Subject: [PATCH RFC v3 8/9] KVM: implement kvm_for_each_vcpu with a list

From: [email-masked] (Christoffer Dall)
Date: Tue, 29 Aug 2017 11:58:59 +0200

On Mon, Aug 21, 2017 at 10:35:29PM +0200, Radim Kr?m?? wrote:
> Going through all VCPUs is more natural with a list and the RCU list can
> work as lockless with our constraints.
> 
> This makes kvm->vcpus lose most users, so it will be easier to make
> something out of it.
> 
> A nice side-effect is that the first argument to the macro is gone.
> ARM code was changed a bit to cope with the loss when working with a
> range 0-n and most other places switched to vcpu->vcpus_idx.
> 
> Signed-off-by: Radim Kr?m?? <[email-masked]>
> ---
>  arch/mips/kvm/mips.c                |  4 +---
>  arch/powerpc/kvm/book3s_32_mmu.c    |  3 +--
>  arch/powerpc/kvm/book3s_64_mmu.c    |  3 +--
>  arch/powerpc/kvm/book3s_hv.c        |  7 +++----
>  arch/powerpc/kvm/book3s_pr.c        |  5 ++---
>  arch/powerpc/kvm/book3s_xics.c      |  2 +-
>  arch/powerpc/kvm/book3s_xics.h      |  3 +--
>  arch/powerpc/kvm/book3s_xive.c      | 18 ++++++++----------
>  arch/powerpc/kvm/book3s_xive.h      |  3 +--
>  arch/powerpc/kvm/e500_emulate.c     |  3 +--
>  arch/powerpc/kvm/powerpc.c          |  3 +--
>  arch/s390/kvm/interrupt.c           |  3 +--
>  arch/s390/kvm/kvm-s390.c            | 31 ++++++++++---------------------
>  arch/s390/kvm/kvm-s390.h            |  6 ++----
>  arch/s390/kvm/sigp.c                |  3 +--
>  arch/x86/kvm/hyperv.c               |  3 +--
>  arch/x86/kvm/i8254.c                |  3 +--
>  arch/x86/kvm/i8259.c                |  7 +++----
>  arch/x86/kvm/ioapic.c               |  3 +--
>  arch/x86/kvm/irq_comm.c             | 10 +++++-----
>  arch/x86/kvm/lapic.c                |  5 ++---
>  arch/x86/kvm/svm.c                  |  3 +--
>  arch/x86/kvm/vmx.c                  |  3 +--
>  arch/x86/kvm/x86.c                  | 25 ++++++++++---------------
>  include/linux/kvm_host.h            | 30 +++++++++++++-----------------
>  virt/kvm/arm/arch_timer.c           | 10 ++++------
>  virt/kvm/arm/arm.c                  | 12 ++++--------
>  virt/kvm/arm/pmu.c                  |  3 +--
>  virt/kvm/arm/psci.c                 |  7 +++----
>  virt/kvm/arm/vgic/vgic-init.c       | 11 +++++------
>  virt/kvm/arm/vgic/vgic-kvm-device.c | 28 ++++++++++++++++------------
>  virt/kvm/arm/vgic/vgic-mmio-v2.c    |  5 ++---
>  virt/kvm/arm/vgic/vgic-mmio-v3.c    | 19 +++++++++++--------
>  virt/kvm/arm/vgic/vgic.c            |  3 +--
>  virt/kvm/kvm_main.c                 | 22 +++++++++++-----------
>  35 files changed, 131 insertions(+), 178 deletions(-)
> 
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index 770c40b9df37..c841cb434486 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -162,12 +162,10 @@ int kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu)
>  
>  void kvm_arch_free_vcpus(struct kvm *kvm)
>  {
> -	unsigned int i;
>  	struct kvm_vcpu *vcpu;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		kvm_arch_vcpu_free(vcpu);
> -	}
>  }
>  
>  static void kvm_mips_free_gpa_pt(struct kvm *kvm)
> diff --git a/arch/powerpc/kvm/book3s_32_mmu.c b/arch/powerpc/kvm/book3s_32_mmu.c
> index 1992676c7a94..1ac7cace49fc 100644
> --- a/arch/powerpc/kvm/book3s_32_mmu.c
> +++ b/arch/powerpc/kvm/book3s_32_mmu.c
> @@ -353,11 +353,10 @@ static void kvmppc_mmu_book3s_32_mtsrin(struct kvm_vcpu *vcpu, u32 srnum,
>  
>  static void kvmppc_mmu_book3s_32_tlbie(struct kvm_vcpu *vcpu, ulong ea, bool large)
>  {
> -	int i;
>  	struct kvm_vcpu *v;
>  
>  	/* flush this VA on all cpus */
> -	kvm_for_each_vcpu(i, v, vcpu->kvm)
> +	kvm_for_each_vcpu(v, vcpu->kvm)
>  		kvmppc_mmu_pte_flush(v, ea, 0x0FFFF000);
>  }
>  
> diff --git a/arch/powerpc/kvm/book3s_64_mmu.c b/arch/powerpc/kvm/book3s_64_mmu.c
> index 29ebe2fd5867..7b043fcc8c88 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu.c
> @@ -534,7 +534,6 @@ static void kvmppc_mmu_book3s_64_tlbie(struct kvm_vcpu *vcpu, ulong va,
>  				       bool large)
>  {
>  	u64 mask = 0xFFFFFFFFFULL;
> -	long i;
>  	struct kvm_vcpu *v;
>  
>  	dprintk("KVM MMU: tlbie(0x%lx)\n", va);
> @@ -559,7 +558,7 @@ static void kvmppc_mmu_book3s_64_tlbie(struct kvm_vcpu *vcpu, ulong va,
>  			mask = 0xFFFFFF000ULL;
>  	}
>  	/* flush this VA on all vcpus */
> -	kvm_for_each_vcpu(i, v, vcpu->kvm)
> +	kvm_for_each_vcpu(v, vcpu->kvm)
>  		kvmppc_mmu_pte_vflush(v, va >> 12, mask);
>  }
>  
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 359c79cdf0cc..4d40537fad20 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -1253,9 +1253,8 @@ static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr,
>  	 */
>  	if ((new_lpcr & LPCR_ILE) != (vc->lpcr & LPCR_ILE)) {
>  		struct kvm_vcpu *vcpu;
> -		int i;
>  
> -		kvm_for_each_vcpu(i, vcpu, kvm) {
> +		kvm_for_each_vcpu(vcpu, kvm) {
>  			if (vcpu->arch.vcore != vc)
>  				continue;
>  			if (new_lpcr & LPCR_ILE)
> @@ -3347,7 +3346,7 @@ static int kvm_vm_ioctl_get_dirty_log_hv(struct kvm *kvm,
>  {
>  	struct kvm_memslots *slots;
>  	struct kvm_memory_slot *memslot;
> -	int i, r;
> +	int r;
>  	unsigned long n;
>  	unsigned long *buf;
>  	struct kvm_vcpu *vcpu;
> @@ -3381,7 +3380,7 @@ static int kvm_vm_ioctl_get_dirty_log_hv(struct kvm *kvm,
>  
>  	/* Harvest dirty bits from VPA and DTL updates */
>  	/* Note: we never modify the SLB shadow buffer areas */
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		spin_lock(&vcpu->arch.vpa_update_lock);
>  		kvmppc_harvest_vpa_dirty(&vcpu->arch.vpa, memslot, buf);
>  		kvmppc_harvest_vpa_dirty(&vcpu->arch.dtl, memslot, buf);
> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
> index 69a09444d46e..9ef1b9b7e48a 100644
> --- a/arch/powerpc/kvm/book3s_pr.c
> +++ b/arch/powerpc/kvm/book3s_pr.c
> @@ -251,7 +251,6 @@ static int kvmppc_core_check_requests_pr(struct kvm_vcpu *vcpu)
>  static void do_kvm_unmap_hva(struct kvm *kvm, unsigned long start,
>  			     unsigned long end)
>  {
> -	long i;
>  	struct kvm_vcpu *vcpu;
>  	struct kvm_memslots *slots;
>  	struct kvm_memory_slot *memslot;
> @@ -272,7 +271,7 @@ static void do_kvm_unmap_hva(struct kvm *kvm, unsigned long start,
>  		 */
>  		gfn = hva_to_gfn_memslot(hva_start, memslot);
>  		gfn_end = hva_to_gfn_memslot(hva_end + PAGE_SIZE - 1, memslot);
> -		kvm_for_each_vcpu(i, vcpu, kvm)
> +		kvm_for_each_vcpu(vcpu, kvm)
>  			kvmppc_mmu_pte_pflush(vcpu, gfn << PAGE_SHIFT,
>  					      gfn_end << PAGE_SHIFT);
>  	}
> @@ -1593,7 +1592,7 @@ static int kvm_vm_ioctl_get_dirty_log_pr(struct kvm *kvm,
>  		ga = memslot->base_gfn << PAGE_SHIFT;
>  		ga_end = ga + (memslot->npages << PAGE_SHIFT);
>  
> -		kvm_for_each_vcpu(n, vcpu, kvm)
> +		kvm_for_each_vcpu(vcpu, kvm)
>  			kvmppc_mmu_pte_pflush(vcpu, ga, ga_end);
>  
>  		n = kvm_dirty_bitmap_bytes(memslot);
> diff --git a/arch/powerpc/kvm/book3s_xics.c b/arch/powerpc/kvm/book3s_xics.c
> index d329b2add7e2..9871b76368bd 100644
> --- a/arch/powerpc/kvm/book3s_xics.c
> +++ b/arch/powerpc/kvm/book3s_xics.c
> @@ -966,7 +966,7 @@ static int xics_debug_show(struct seq_file *m, void *private)
>  
>  	seq_printf(m, "=========\nICP state\n=========\n");
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		struct kvmppc_icp *icp = vcpu->arch.icp;
>  		union kvmppc_icp_state state;
>  
> diff --git a/arch/powerpc/kvm/book3s_xics.h b/arch/powerpc/kvm/book3s_xics.h
> index 453c9e518c19..71e33af1e119 100644
> --- a/arch/powerpc/kvm/book3s_xics.h
> +++ b/arch/powerpc/kvm/book3s_xics.h
> @@ -119,9 +119,8 @@ static inline struct kvmppc_icp *kvmppc_xics_find_server(struct kvm *kvm,
>  							 u32 nr)
>  {
>  	struct kvm_vcpu *vcpu = NULL;
> -	int i;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		if (vcpu->arch.icp && nr == vcpu->arch.icp->server_num)
>  			return vcpu->arch.icp;
>  	}
> diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c
> index 08b200a0bbce..22222a540439 100644
> --- a/arch/powerpc/kvm/book3s_xive.c
> +++ b/arch/powerpc/kvm/book3s_xive.c
> @@ -182,7 +182,7 @@ static int xive_check_provisioning(struct kvm *kvm, u8 prio)
>  {
>  	struct kvmppc_xive *xive = kvm->arch.xive;
>  	struct kvm_vcpu *vcpu;
> -	int i, rc;
> +	int rc;
>  
>  	lockdep_assert_held(&kvm->lock);
>  
> @@ -193,7 +193,7 @@ static int xive_check_provisioning(struct kvm *kvm, u8 prio)
>  	pr_devel("Provisioning prio... %d\n", prio);
>  
>  	/* Provision each VCPU and enable escalations */
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		if (!vcpu->arch.xive_vcpu)
>  			continue;
>  		rc = xive_provision_queue(vcpu, prio);
> @@ -252,7 +252,7 @@ static int xive_try_pick_queue(struct kvm_vcpu *vcpu, u8 prio)
>  static int xive_select_target(struct kvm *kvm, u32 *server, u8 prio)
>  {
>  	struct kvm_vcpu *vcpu;
> -	int i, rc;
> +	int rc;
>  
>  	/* Locate target server */
>  	vcpu = kvmppc_xive_find_server(kvm, *server);
> @@ -271,7 +271,7 @@ static int xive_select_target(struct kvm *kvm, u32 *server, u8 prio)
>  	pr_devel(" .. failed, looking up candidate...\n");
>  
>  	/* Failed, pick another VCPU */
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		if (!vcpu->arch.xive_vcpu)
>  			continue;
>  		rc = xive_try_pick_queue(vcpu, prio);
> @@ -1237,7 +1237,7 @@ static void xive_pre_save_queue(struct kvmppc_xive *xive, struct xive_q *q)
>  static void xive_pre_save_scan(struct kvmppc_xive *xive)
>  {
>  	struct kvm_vcpu *vcpu = NULL;
> -	int i, j;
> +	int j;
>  
>  	/*
>  	 * See comment in xive_get_source() about how this
> @@ -1252,7 +1252,7 @@ static void xive_pre_save_scan(struct kvmppc_xive *xive)
>  	}
>  
>  	/* Then scan the queues and update the "in_queue" flag */
> -	kvm_for_each_vcpu(i, vcpu, xive->kvm) {
> +	kvm_for_each_vcpu(vcpu, xive->kvm) {
>  		struct kvmppc_xive_vcpu *xc = vcpu->arch.xive_vcpu;
>  		if (!xc)
>  			continue;
> @@ -1418,9 +1418,8 @@ static bool xive_check_delayed_irq(struct kvmppc_xive *xive, u32 irq)
>  {
>  	struct kvm *kvm = xive->kvm;
>  	struct kvm_vcpu *vcpu = NULL;
> -	int i;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		struct kvmppc_xive_vcpu *xc = vcpu->arch.xive_vcpu;
>  
>  		if (!xc)
> @@ -1787,14 +1786,13 @@ static int xive_debug_show(struct seq_file *m, void *private)
>  	u64 t_vm_h_cppr = 0;
>  	u64 t_vm_h_eoi = 0;
>  	u64 t_vm_h_ipi = 0;
> -	unsigned int i;
>  
>  	if (!kvm)
>  		return 0;
>  
>  	seq_printf(m, "=========\nVCPU state\n=========\n");
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		struct kvmppc_xive_vcpu *xc = vcpu->arch.xive_vcpu;
>  
>  		if (!xc)
> diff --git a/arch/powerpc/kvm/book3s_xive.h b/arch/powerpc/kvm/book3s_xive.h
> index 5938f7644dc1..5bc33db0924c 100644
> --- a/arch/powerpc/kvm/book3s_xive.h
> +++ b/arch/powerpc/kvm/book3s_xive.h
> @@ -175,9 +175,8 @@ struct kvmppc_xive_vcpu {
>  static inline struct kvm_vcpu *kvmppc_xive_find_server(struct kvm *kvm, u32 nr)
>  {
>  	struct kvm_vcpu *vcpu = NULL;
> -	int i;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		if (vcpu->arch.xive_vcpu && nr == vcpu->arch.xive_vcpu->server_num)
>  			return vcpu;
>  	}
> diff --git a/arch/powerpc/kvm/e500_emulate.c b/arch/powerpc/kvm/e500_emulate.c
> index 990db69a1d0b..56151681afcc 100644
> --- a/arch/powerpc/kvm/e500_emulate.c
> +++ b/arch/powerpc/kvm/e500_emulate.c
> @@ -68,13 +68,12 @@ static int kvmppc_e500_emul_msgsnd(struct kvm_vcpu *vcpu, int rb)
>  	ulong param = vcpu->arch.gpr[rb];
>  	int prio = dbell2prio(rb);
>  	int pir = param & PPC_DBELL_PIR_MASK;
> -	int i;
>  	struct kvm_vcpu *cvcpu;
>  
>  	if (prio < 0)
>  		return EMULATE_FAIL;
>  
> -	kvm_for_each_vcpu(i, cvcpu, vcpu->kvm) {
> +	kvm_for_each_vcpu(cvcpu, vcpu->kvm) {
>  		int cpir = cvcpu->arch.shared->pir;
>  		if ((param & PPC_DBELL_MSG_BRDCAST) || (cpir == pir)) {
>  			set_bit(prio, &cvcpu->arch.pending_exceptions);
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 1c563545473c..633d3bb501c1 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -458,10 +458,9 @@ int kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu)
>  
>  void kvm_arch_free_vcpus(struct kvm *kvm)
>  {
> -	int i;
>  	struct kvm_vcpu *vcpu;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		kvm_arch_vcpu_free(vcpu);
>  }
>  
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index a619ddae610d..d503b25638af 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -2287,7 +2287,6 @@ static int flic_ais_mode_set_all(struct kvm *kvm, struct kvm_device_attr *attr)
>  static int flic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
>  {
>  	int r = 0;
> -	unsigned int i;
>  	struct kvm_vcpu *vcpu;
>  
>  	switch (attr->group) {
> @@ -2308,7 +2307,7 @@ static int flic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
>  		 * about late coming workers.
>  		 */
>  		synchronize_srcu(&dev->kvm->srcu);
> -		kvm_for_each_vcpu(i, vcpu, dev->kvm)
> +		kvm_for_each_vcpu(vcpu, dev->kvm)
>  			kvm_clear_async_pf_completion_queue(vcpu);
>  		break;
>  	case KVM_DEV_FLIC_ADAPTER_REGISTER:
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index bb6278d45a25..3e64e3eb2a63 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -174,12 +174,11 @@ static int kvm_clock_sync(struct notifier_block *notifier, unsigned long val,
>  {
>  	struct kvm *kvm;
>  	struct kvm_vcpu *vcpu;
> -	int i;
>  	unsigned long long *delta = v;
>  
>  	list_for_each_entry(kvm, &vm_list, vm_list) {
>  		kvm->arch.epoch -= *delta;
> -		kvm_for_each_vcpu(i, vcpu, kvm) {
> +		kvm_for_each_vcpu(vcpu, kvm) {
>  			vcpu->arch.sie_block->epoch -= *delta;
>  			if (vcpu->arch.cputm_enabled)
>  				vcpu->arch.cputm_start += *delta;
> @@ -491,12 +490,10 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
>  
>  static void icpt_operexc_on_all_vcpus(struct kvm *kvm)
>  {
> -	unsigned int i;
>  	struct kvm_vcpu *vcpu;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		kvm_s390_sync_request(KVM_REQ_ICPT_OPEREXC, vcpu);
> -	}
>  }
>  
>  static int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
> @@ -705,7 +702,6 @@ static void kvm_s390_vcpu_crypto_setup(struct kvm_vcpu *vcpu);
>  static int kvm_s390_vm_set_crypto(struct kvm *kvm, struct kvm_device_attr *attr)
>  {
>  	struct kvm_vcpu *vcpu;
> -	int i;
>  
>  	if (!test_kvm_facility(kvm, 76))
>  		return -EINVAL;
> @@ -743,7 +739,7 @@ static int kvm_s390_vm_set_crypto(struct kvm *kvm, struct kvm_device_attr *attr)
>  		return -ENXIO;
>  	}
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		kvm_s390_vcpu_crypto_setup(vcpu);
>  		exit_sie(vcpu);
>  	}
> @@ -753,10 +749,9 @@ static int kvm_s390_vm_set_crypto(struct kvm *kvm, struct kvm_device_attr *attr)
>  
>  static void kvm_s390_sync_request_broadcast(struct kvm *kvm, int req)
>  {
> -	int cx;
>  	struct kvm_vcpu *vcpu;
>  
> -	kvm_for_each_vcpu(cx, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		kvm_s390_sync_request(req, vcpu);
>  }
>  
> @@ -1943,10 +1938,9 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
>  
>  void kvm_arch_free_vcpus(struct kvm *kvm)
>  {
> -	unsigned int i;
>  	struct kvm_vcpu *vcpu;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		kvm_arch_vcpu_destroy(vcpu);
>  }
>  
> @@ -2050,7 +2044,6 @@ static int sca_switch_to_extended(struct kvm *kvm)
>  	struct bsca_block *old_sca = kvm->arch.sca;
>  	struct esca_block *new_sca;
>  	struct kvm_vcpu *vcpu;
> -	unsigned int vcpu_idx;
>  	u32 scaol, scaoh;
>  
>  	new_sca = alloc_pages_exact(sizeof(*new_sca), GFP_KERNEL|__GFP_ZERO);
> @@ -2065,7 +2058,7 @@ static int sca_switch_to_extended(struct kvm *kvm)
>  
>  	sca_copy_b_to_e(new_sca, old_sca);
>  
> -	kvm_for_each_vcpu(vcpu_idx, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		vcpu->arch.sie_block->scaoh = scaoh;
>  		vcpu->arch.sie_block->scaol = scaol;
>  		vcpu->arch.sie_block->ecb2 |= ECB2_ESCA;
> @@ -2491,14 +2484,13 @@ static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start,
>  	struct kvm *kvm = gmap->private;
>  	struct kvm_vcpu *vcpu;
>  	unsigned long prefix;
> -	int i;
>  
>  	if (gmap_is_shadow(gmap))
>  		return;
>  	if (start >= 1UL << 31)
>  		/* We are only interested in prefix pages */
>  		return;
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		/* match against both prefix pages */
>  		prefix = kvm_s390_get_prefix(vcpu);
>  		if (prefix <= end && start <= prefix + 2*PAGE_SIZE - 1) {
> @@ -2856,13 +2848,12 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
>  void kvm_s390_set_tod_clock(struct kvm *kvm, u64 tod)
>  {
>  	struct kvm_vcpu *vcpu;
> -	int i;
>  
>  	mutex_lock(&kvm->lock);
>  	preempt_disable();
>  	kvm->arch.epoch = tod - get_tod_clock();
>  	kvm_s390_vcpu_block_all(kvm);
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		vcpu->arch.sie_block->epoch = kvm->arch.epoch;
>  	kvm_s390_vcpu_unblock_all(kvm);
>  	preempt_enable();
> @@ -3389,12 +3380,10 @@ static void __disable_ibs_on_vcpu(struct kvm_vcpu *vcpu)
>  
>  static void __disable_ibs_on_all_vcpus(struct kvm *kvm)
>  {
> -	unsigned int i;
>  	struct kvm_vcpu *vcpu;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		__disable_ibs_on_vcpu(vcpu);
> -	}
>  }
>  
>  static void __enable_ibs_on_vcpu(struct kvm_vcpu *vcpu)
> @@ -3462,7 +3451,7 @@ void kvm_s390_vcpu_stop(struct kvm_vcpu *vcpu)
>  		 * As we only have one VCPU left, we want to enable the IBS
>  		 * facility for that VCPU to speed it up.
>  		 */
> -		kvm_for_each_vcpu(i, started_vcpu, vcpu->kvm)
> +		kvm_for_each_vcpu(started_vcpu, vcpu->kvm)
>  			if (!is_vcpu_stopped(started_vcpu)) {
>  				__enable_ibs_on_vcpu(started_vcpu);
>  				break;
> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
> index 6fedc8bc7a37..6077a724630c 100644
> --- a/arch/s390/kvm/kvm-s390.h
> +++ b/arch/s390/kvm/kvm-s390.h
> @@ -294,20 +294,18 @@ int kvm_s390_handle_diag(struct kvm_vcpu *vcpu);
>  
>  static inline void kvm_s390_vcpu_block_all(struct kvm *kvm)
>  {
> -	int i;
>  	struct kvm_vcpu *vcpu;
>  
>  	WARN_ON(!mutex_is_locked(&kvm->lock));
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		kvm_s390_vcpu_block(vcpu);
>  }
>  
>  static inline void kvm_s390_vcpu_unblock_all(struct kvm *kvm)
>  {
> -	int i;
>  	struct kvm_vcpu *vcpu;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		kvm_s390_vcpu_unblock(vcpu);
>  }
>  
> diff --git a/arch/s390/kvm/sigp.c b/arch/s390/kvm/sigp.c
> index 1a252f537081..a31e1c2a994d 100644
> --- a/arch/s390/kvm/sigp.c
> +++ b/arch/s390/kvm/sigp.c
> @@ -158,7 +158,6 @@ static int __sigp_stop_and_store_status(struct kvm_vcpu *vcpu,
>  static int __sigp_set_arch(struct kvm_vcpu *vcpu, u32 parameter)
>  {
>  	int rc;
> -	unsigned int i;
>  	struct kvm_vcpu *v;
>  
>  	switch (parameter & 0xff) {
> @@ -167,7 +166,7 @@ static int __sigp_set_arch(struct kvm_vcpu *vcpu, u32 parameter)
>  		break;
>  	case 1:
>  	case 2:
> -		kvm_for_each_vcpu(i, v, vcpu->kvm) {
> +		kvm_for_each_vcpu(v, vcpu->kvm) {
>  			v->arch.pfault_token = KVM_S390_PFAULT_TOKEN_INVALID;
>  			kvm_clear_async_pf_completion_queue(v);
>  		}
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index dc97f2544b6f..b43cb27bf783 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -109,13 +109,12 @@ static int synic_set_sint(struct kvm_vcpu_hv_synic *synic, int sint,
>  static struct kvm_vcpu *get_vcpu_by_vpidx(struct kvm *kvm, u32 vpidx)
>  {
>  	struct kvm_vcpu *vcpu = NULL;
> -	int i;
>  
>  	if (vpidx < KVM_MAX_VCPUS)
>  		vcpu = kvm_get_vcpu(kvm, vpidx);
>  	if (vcpu && vcpu_to_hv_vcpu(vcpu)->vp_index == vpidx)
>  		return vcpu;
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		if (vcpu_to_hv_vcpu(vcpu)->vp_index == vpidx)
>  			return vcpu;
>  	return NULL;
> diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
> index af192895b1fc..fdd3bff598f3 100644
> --- a/arch/x86/kvm/i8254.c
> +++ b/arch/x86/kvm/i8254.c
> @@ -241,7 +241,6 @@ static void pit_do_work(struct kthread_work *work)
>  	struct kvm_pit *pit = container_of(work, struct kvm_pit, expired);
>  	struct kvm *kvm = pit->kvm;
>  	struct kvm_vcpu *vcpu;
> -	int i;
>  	struct kvm_kpit_state *ps = &pit->pit_state;
>  
>  	if (atomic_read(&ps->reinject) && !atomic_xchg(&ps->irq_ack, 0))
> @@ -260,7 +259,7 @@ static void pit_do_work(struct kthread_work *work)
>  	 * also be simultaneously delivered through PIC and IOAPIC.
>  	 */
>  	if (atomic_read(&kvm->arch.vapics_in_nmi_mode) > 0)
> -		kvm_for_each_vcpu(i, vcpu, kvm)
> +		kvm_for_each_vcpu(vcpu, kvm)
>  			kvm_apic_nmi_wd_deliver(vcpu);
>  }
>  
> diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
> index bdcd4139eca9..c4f57fbd7316 100644
> --- a/arch/x86/kvm/i8259.c
> +++ b/arch/x86/kvm/i8259.c
> @@ -50,14 +50,13 @@ static void pic_unlock(struct kvm_pic *s)
>  {
>  	bool wakeup = s->wakeup_needed;
>  	struct kvm_vcpu *vcpu;
> -	int i;
>  
>  	s->wakeup_needed = false;
>  
>  	spin_unlock(&s->lock);
>  
>  	if (wakeup) {
> -		kvm_for_each_vcpu(i, vcpu, s->kvm) {
> +		kvm_for_each_vcpu(vcpu, s->kvm) {
>  			if (kvm_apic_accept_pic_intr(vcpu)) {
>  				kvm_make_request(KVM_REQ_EVENT, vcpu);
>  				kvm_vcpu_kick(vcpu);
> @@ -270,7 +269,7 @@ int kvm_pic_read_irq(struct kvm *kvm)
>  
>  static void kvm_pic_reset(struct kvm_kpic_state *s)
>  {
> -	int irq, i;
> +	int irq;
>  	struct kvm_vcpu *vcpu;
>  	u8 edge_irr = s->irr & ~s->elcr;
>  	bool found = false;
> @@ -287,7 +286,7 @@ static void kvm_pic_reset(struct kvm_kpic_state *s)
>  	}
>  	s->init_state = 1;
>  
> -	kvm_for_each_vcpu(i, vcpu, s->pics_state->kvm)
> +	kvm_for_each_vcpu(vcpu, s->pics_state->kvm)
>  		if (kvm_apic_accept_pic_intr(vcpu)) {
>  			found = true;
>  			break;
> diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
> index 1a29da6c0558..2216e6d34fb7 100644
> --- a/arch/x86/kvm/ioapic.c
> +++ b/arch/x86/kvm/ioapic.c
> @@ -146,13 +146,12 @@ void kvm_rtc_eoi_tracking_restore_one(struct kvm_vcpu *vcpu)
>  static void kvm_rtc_eoi_tracking_restore_all(struct kvm_ioapic *ioapic)
>  {
>  	struct kvm_vcpu *vcpu;
> -	int i;
>  
>  	if (RTC_GSI >= IOAPIC_NUM_PINS)
>  		return;
>  
>  	rtc_irq_eoi_tracking_reset(ioapic);
> -	kvm_for_each_vcpu(i, vcpu, ioapic->kvm)
> +	kvm_for_each_vcpu(vcpu, ioapic->kvm)
>  	    __rtc_irq_eoi_tracking_restore_one(vcpu);
>  }
>  
> diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
> index 3cc3b2d130a0..a8f777f2b0e6 100644
> --- a/arch/x86/kvm/irq_comm.c
> +++ b/arch/x86/kvm/irq_comm.c
> @@ -58,7 +58,7 @@ static int kvm_set_ioapic_irq(struct kvm_kernel_irq_routing_entry *e,
>  int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
>  		struct kvm_lapic_irq *irq, struct dest_map *dest_map)
>  {
> -	int i, r = -1;
> +	int r = -1;
>  	struct kvm_vcpu *vcpu, *lowest = NULL;
>  	unsigned long dest_vcpu_bitmap[BITS_TO_LONGS(KVM_MAX_VCPUS)];
>  	unsigned int dest_vcpus = 0;
> @@ -74,7 +74,7 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
>  
>  	memset(dest_vcpu_bitmap, 0, sizeof(dest_vcpu_bitmap));
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		if (!kvm_apic_present(vcpu))
>  			continue;
>  
> @@ -93,7 +93,7 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
>  				else if (kvm_apic_compare_prio(vcpu, lowest) < 0)
>  					lowest = vcpu;
>  			} else {
> -				__set_bit(i, dest_vcpu_bitmap);
> +				__set_bit(vcpu->vcpus_idx, dest_vcpu_bitmap);
>  				dest_vcpus++;
>  			}
>  		}
> @@ -335,13 +335,13 @@ int kvm_set_routing_entry(struct kvm *kvm,
>  bool kvm_intr_is_single_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
>  			     struct kvm_vcpu **dest_vcpu)
>  {
> -	int i, r = 0;
> +	int r = 0;
>  	struct kvm_vcpu *vcpu;
>  
>  	if (kvm_intr_is_single_vcpu_fast(kvm, irq, dest_vcpu))
>  		return true;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		if (!kvm_apic_present(vcpu))
>  			continue;
>  
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 4f38818db929..a7cdd6baa38b 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -166,12 +166,11 @@ static void recalculate_apic_map(struct kvm *kvm)
>  {
>  	struct kvm_apic_map *new, *old = NULL;
>  	struct kvm_vcpu *vcpu;
> -	int i;
>  	u32 max_id = 255; /* enough space for any xAPIC ID */
>  
>  	mutex_lock(&kvm->arch.apic_map_lock);
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		if (kvm_apic_present(vcpu))
>  			max_id = max(max_id, kvm_x2apic_id(vcpu->arch.apic));
>  
> @@ -183,7 +182,7 @@ static void recalculate_apic_map(struct kvm *kvm)
>  
>  	new->max_apic_id = max_id;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		struct kvm_lapic *apic = vcpu->arch.apic;
>  		struct kvm_lapic **cluster;
>  		u16 mask;
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 1fa9ee5660f4..605c18003f55 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -3807,7 +3807,6 @@ static int avic_incomplete_ipi_interception(struct vcpu_svm *svm)
>  		kvm_lapic_reg_write(apic, APIC_ICR, icrl);
>  		break;
>  	case AVIC_IPI_FAILURE_TARGET_NOT_RUNNING: {
> -		int i;
>  		struct kvm_vcpu *vcpu;
>  		struct kvm *kvm = svm->vcpu.kvm;
>  		struct kvm_lapic *apic = svm->vcpu.arch.apic;
> @@ -3817,7 +3816,7 @@ static int avic_incomplete_ipi_interception(struct vcpu_svm *svm)
>  		 * set the appropriate IRR bits on the valid target
>  		 * vcpus. So, we just need to kick the appropriate vcpu.
>  		 */
> -		kvm_for_each_vcpu(i, vcpu, kvm) {
> +		kvm_for_each_vcpu(vcpu, kvm) {
>  			bool m = kvm_apic_match_dest(vcpu, apic,
>  						     icrl & KVM_APIC_SHORT_MASK,
>  						     GET_APIC_DEST_FIELD(icrh),
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index df8d2f127508..ae0f04e26fec 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -8472,7 +8472,6 @@ static void vmx_flush_pml_buffer(struct kvm_vcpu *vcpu)
>   */
>  static void kvm_flush_pml_buffers(struct kvm *kvm)
>  {
> -	int i;
>  	struct kvm_vcpu *vcpu;
>  	/*
>  	 * We only need to kick vcpu out of guest mode here, as PML buffer
> @@ -8480,7 +8479,7 @@ static void kvm_flush_pml_buffers(struct kvm *kvm)
>  	 * vcpus running in guest are possible to have unflushed GPAs in PML
>  	 * buffer.
>  	 */
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		kvm_vcpu_kick(vcpu);
>  }
>  
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index d021746f1fdf..caea24d3ddb0 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1734,7 +1734,6 @@ void kvm_make_mclock_inprogress_request(struct kvm *kvm)
>  static void kvm_gen_update_masterclock(struct kvm *kvm)
>  {
>  #ifdef CONFIG_X86_64
> -	int i;
>  	struct kvm_vcpu *vcpu;
>  	struct kvm_arch *ka = &kvm->arch;
>  
> @@ -1743,11 +1742,11 @@ static void kvm_gen_update_masterclock(struct kvm *kvm)
>  	/* no guest entries from this point */
>  	pvclock_update_vm_gtod_copy(kvm);
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
>  
>  	/* guest entries allowed */
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		kvm_clear_request(KVM_REQ_MCLOCK_INPROGRESS, vcpu);
>  
>  	spin_unlock(&ka->pvclock_gtod_sync_lock);
> @@ -1945,14 +1944,13 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
>  
>  static void kvmclock_update_fn(struct work_struct *work)
>  {
> -	int i;
>  	struct delayed_work *dwork = to_delayed_work(work);
>  	struct kvm_arch *ka = container_of(dwork, struct kvm_arch,
>  					   kvmclock_update_work);
>  	struct kvm *kvm = container_of(ka, struct kvm, arch);
>  	struct kvm_vcpu *vcpu;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
>  		kvm_vcpu_kick(vcpu);
>  	}
> @@ -5844,7 +5842,7 @@ static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long va
>  	struct cpufreq_freqs *freq = data;
>  	struct kvm *kvm;
>  	struct kvm_vcpu *vcpu;
> -	int i, send_ipi = 0;
> +	int send_ipi = 0;
>  
>  	/*
>  	 * We allow guests to temporarily run on slowing clocks,
> @@ -5894,7 +5892,7 @@ static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long va
>  
>  	spin_lock(&kvm_lock);
>  	list_for_each_entry(kvm, &vm_list, vm_list) {
> -		kvm_for_each_vcpu(i, vcpu, kvm) {
> +		kvm_for_each_vcpu(vcpu, kvm) {
>  			if (vcpu->cpu != freq->cpu)
>  				continue;
>  			kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
> @@ -6035,11 +6033,10 @@ static void pvclock_gtod_update_fn(struct work_struct *work)
>  	struct kvm *kvm;
>  
>  	struct kvm_vcpu *vcpu;
> -	int i;
>  
>  	spin_lock(&kvm_lock);
>  	list_for_each_entry(kvm, &vm_list, vm_list)
> -		kvm_for_each_vcpu(i, vcpu, kvm)
> +		kvm_for_each_vcpu(vcpu, kvm)
>  			kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);
>  	atomic_set(&kvm_guest_has_master_clock, 0);
>  	spin_unlock(&kvm_lock);
> @@ -7783,7 +7780,6 @@ int kvm_arch_hardware_enable(void)
>  {
>  	struct kvm *kvm;
>  	struct kvm_vcpu *vcpu;
> -	int i;
>  	int ret;
>  	u64 local_tsc;
>  	u64 max_tsc = 0;
> @@ -7797,7 +7793,7 @@ int kvm_arch_hardware_enable(void)
>  	local_tsc = rdtsc();
>  	stable = !check_tsc_unstable();
>  	list_for_each_entry(kvm, &vm_list, vm_list) {
> -		kvm_for_each_vcpu(i, vcpu, kvm) {
> +		kvm_for_each_vcpu(vcpu, kvm) {
>  			if (!stable && vcpu->cpu == smp_processor_id())
>  				kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
>  			if (stable && vcpu->arch.last_host_tsc > local_tsc) {
> @@ -7850,7 +7846,7 @@ int kvm_arch_hardware_enable(void)
>  		u64 delta_cyc = max_tsc - local_tsc;
>  		list_for_each_entry(kvm, &vm_list, vm_list) {
>  			kvm->arch.backwards_tsc_observed = true;
> -			kvm_for_each_vcpu(i, vcpu, kvm) {
> +			kvm_for_each_vcpu(vcpu, kvm) {
>  				vcpu->arch.tsc_offset_adjustment += delta_cyc;
>  				vcpu->arch.last_host_tsc = local_tsc;
>  				kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);
> @@ -8079,17 +8075,16 @@ static void kvm_unload_vcpu_mmu(struct kvm_vcpu *vcpu)
>  
>  void kvm_arch_free_vcpus(struct kvm *kvm)
>  {
> -	unsigned int i;
>  	struct kvm_vcpu *vcpu;
>  
>  	/*
>  	 * Unpin any mmu pages first.
>  	 */
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		kvm_clear_async_pf_completion_queue(vcpu);
>  		kvm_unload_vcpu_mmu(vcpu);
>  	}
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		kvm_arch_vcpu_free(vcpu);
>  }
>  
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index a8b9aa563834..5417dac55272 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -216,6 +216,7 @@ struct kvm_mmio_fragment {
>  
>  struct kvm_vcpu {
>  	struct kvm *kvm;
> +	struct list_head vcpu_list;
>  #ifdef CONFIG_PREEMPT_NOTIFIERS
>  	struct preempt_notifier preempt_notifier;
>  #endif
> @@ -393,6 +394,7 @@ struct kvm {
>  	struct mm_struct *mm; /* userspace tied to this vm */
>  	struct kvm_memslots __rcu *memslots[KVM_ADDRESS_SPACE_NUM];
>  	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
> +	struct list_head vcpu_list;
>  
>  	/*
>  	 * created_vcpus is protected by kvm->lock, and is incremented
> @@ -402,7 +404,7 @@ struct kvm {
>  	 */
>  	atomic_t online_vcpus;
>  	int created_vcpus;
> -	int last_boosted_vcpu;
> +	struct kvm_vcpu *last_boosted_vcpu;
>  	struct list_head vm_list;
>  	struct mutex lock;
>  	struct kvm_io_bus __rcu *buses[KVM_NR_BUSES];
> @@ -492,29 +494,23 @@ static inline struct kvm_vcpu *kvm_get_vcpu(struct kvm *kvm, int i)
>  	return kvm->vcpus[i];
>  }
>  
> -#define kvm_for_each_vcpu(idx, vcpup, kvm) \
> -	for (idx = 0; \
> -	     idx < atomic_read(&kvm->online_vcpus) && \
> -	     (vcpup = kvm_get_vcpu(kvm, idx)) != NULL; \
> -	     idx++)
> +#define kvm_for_each_vcpu(vcpup, kvm) \
> +	list_for_each_entry_rcu(vcpup, &kvm->vcpu_list, vcpu_list)
>  
> -#define kvm_for_each_vcpu_from(idx, vcpup, from, kvm) \
> -	for (idx = from, vcpup = kvm_get_vcpu(kvm, idx); \
> +#define kvm_for_each_vcpu_from(vcpup, from, kvm) \
> +	for (vcpup = from; \
>  	     vcpup; \
>  	     ({ \
> -		idx++; \
> -		if (idx >= atomic_read(&kvm->online_vcpus)) \
> -			idx = 0; \
> -		if (idx == from) \
> +		vcpup = list_entry_rcu(vcpup->vcpu_list.next, typeof(*vcpup), vcpu_list); \
> +		if (&vcpup->vcpu_list == &kvm->vcpu_list) \
> +			vcpup = list_entry_rcu(kvm->vcpu_list.next, typeof(*vcpup), vcpu_list); \
> +		if (vcpup == from) \
>  			vcpup = NULL; \
> -		else \
> -			vcpup = kvm_get_vcpu(kvm, idx); \
> -	      }))
> +	     }))
>  
>  static inline struct kvm_vcpu *kvm_get_vcpu_by_id(struct kvm *kvm, int id)
>  {
>  	struct kvm_vcpu *vcpu = NULL;
> -	int i;
>  
>  	if (id < 0)
>  		return NULL;
> @@ -522,7 +518,7 @@ static inline struct kvm_vcpu *kvm_get_vcpu_by_id(struct kvm *kvm, int id)
>  		vcpu = kvm_get_vcpu(kvm, id);
>  	if (vcpu && vcpu->vcpu_id == id)
>  		return vcpu;
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		if (vcpu->vcpu_id == id)
>  			return vcpu;
>  	return NULL;
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index 8e89d63005c7..3e311fa5c7a1 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -478,12 +478,11 @@ int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu)
>  /* Make the updates of cntvoff for all vtimer contexts atomic */
>  static void update_vtimer_cntvoff(struct kvm_vcpu *vcpu, u64 cntvoff)
>  {
> -	int i;
>  	struct kvm *kvm = vcpu->kvm;
>  	struct kvm_vcpu *tmp;
>  
>  	mutex_lock(&kvm->lock);
> -	kvm_for_each_vcpu(i, tmp, kvm)
> +	kvm_for_each_vcpu(tmp, kvm)
>  		vcpu_vtimer(tmp)->cntvoff = cntvoff;
>  
>  	/*
> @@ -622,7 +621,7 @@ void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu)
>  static bool timer_irqs_are_valid(struct kvm_vcpu *vcpu)
>  {
>  	int vtimer_irq, ptimer_irq;
> -	int i, ret;
> +	int ret;
>  
>  	vtimer_irq = vcpu_vtimer(vcpu)->irq.irq;
>  	ret = kvm_vgic_set_owner(vcpu, vtimer_irq, vcpu_vtimer(vcpu));
> @@ -634,7 +633,7 @@ static bool timer_irqs_are_valid(struct kvm_vcpu *vcpu)
>  	if (ret)
>  		return false;
>  
> -	kvm_for_each_vcpu(i, vcpu, vcpu->kvm) {
> +	kvm_for_each_vcpu(vcpu, vcpu->kvm) {
>  		if (vcpu_vtimer(vcpu)->irq.irq != vtimer_irq ||
>  		    vcpu_ptimer(vcpu)->irq.irq != ptimer_irq)
>  			return false;
> @@ -720,9 +719,8 @@ void kvm_timer_init_vhe(void)
>  static void set_timer_irqs(struct kvm *kvm, int vtimer_irq, int ptimer_irq)
>  {
>  	struct kvm_vcpu *vcpu;
> -	int i;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		vcpu_vtimer(vcpu)->irq.irq = vtimer_irq;
>  		vcpu_ptimer(vcpu)->irq.irq = ptimer_irq;
>  	}
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index d63aa1107fdb..e105f6b307cc 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -168,10 +168,9 @@ int kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf)
>  
>  void kvm_arch_free_vcpus(struct kvm *kvm)
>  {
> -	int i;
>  	struct kvm_vcpu *vcpu;
>  
> -	for_each_online_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		kvm_arch_vcpu_free(vcpu);
>  }
>  
> @@ -548,20 +547,18 @@ bool kvm_arch_intc_initialized(struct kvm *kvm)
>  
>  void kvm_arm_halt_guest(struct kvm *kvm)
>  {
> -	int i;
>  	struct kvm_vcpu *vcpu;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		vcpu->arch.pause = true;
>  	kvm_make_all_cpus_request(kvm, KVM_REQ_SLEEP);
>  }
>  
>  void kvm_arm_resume_guest(struct kvm *kvm)
>  {
> -	int i;
>  	struct kvm_vcpu *vcpu;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		vcpu->arch.pause = false;
>  		swake_up(kvm_arch_vcpu_wq(vcpu));
>  	}
> @@ -1440,10 +1437,9 @@ static void check_kvm_target_cpu(void *ret)
>  struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr)
>  {
>  	struct kvm_vcpu *vcpu;
> -	int i;
>  
>  	mpidr &= MPIDR_HWID_BITMASK;
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		if (mpidr == kvm_vcpu_get_mpidr_aff(vcpu))
>  			return vcpu;
>  	}
> diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> index 8a9c42366db7..84f526cfdb35 100644
> --- a/virt/kvm/arm/pmu.c
> +++ b/virt/kvm/arm/pmu.c
> @@ -512,10 +512,9 @@ static int kvm_arm_pmu_v3_init(struct kvm_vcpu *vcpu)
>   */
>  static bool pmu_irq_is_valid(struct kvm *kvm, int irq)
>  {
> -	int i;
>  	struct kvm_vcpu *vcpu;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> +	kvm_for_each_vcpu(vcpu, kvm) {
>  		if (!kvm_arm_pmu_irq_initialized(vcpu))
>  			continue;
>  
> diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c
> index f1e363bab5e8..876c965e0886 100644
> --- a/virt/kvm/arm/psci.c
> +++ b/virt/kvm/arm/psci.c
> @@ -129,7 +129,7 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
>  
>  static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
>  {
> -	int i, matching_cpus = 0;
> +	int matching_cpus = 0;
>  	unsigned long mpidr;
>  	unsigned long target_affinity;
>  	unsigned long target_affinity_mask;
> @@ -152,7 +152,7 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
>  	 * If one or more VCPU matching target affinity are running
>  	 * then ON else OFF
>  	 */
> -	kvm_for_each_vcpu(i, tmp, kvm) {
> +	kvm_for_each_vcpu(tmp, kvm) {
>  		mpidr = kvm_vcpu_get_mpidr_aff(tmp);
>  		if ((mpidr & target_affinity_mask) == target_affinity) {
>  			matching_cpus++;
> @@ -169,7 +169,6 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
>  
>  static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
>  {
> -	int i;
>  	struct kvm_vcpu *tmp;
>  
>  	/*
> @@ -181,7 +180,7 @@ static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
>  	 * after this call is handled and before the VCPUs have been
>  	 * re-initialized.
>  	 */
> -	kvm_for_each_vcpu(i, tmp, vcpu->kvm)
> +	kvm_for_each_vcpu(tmp, vcpu->kvm)
>  		tmp->arch.power_off = true;
>  	kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_SLEEP);
>  
> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
> index feb766f74c34..c926d7b30149 100644
> --- a/virt/kvm/arm/vgic/vgic-init.c
> +++ b/virt/kvm/arm/vgic/vgic-init.c
> @@ -119,7 +119,7 @@ void kvm_vgic_vcpu_early_init(struct kvm_vcpu *vcpu)
>   */
>  int kvm_vgic_create(struct kvm *kvm, u32 type)
>  {
> -	int i, ret;
> +	int ret;
>  	struct kvm_vcpu *vcpu;
>  
>  	if (irqchip_in_kernel(kvm))
> @@ -143,7 +143,7 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
>  	if (!lock_all_vcpus(kvm))
>  		return -EBUSY;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		if (vcpu->arch.has_run_once) {
>  			ret = -EBUSY;
>  			goto out_unlock;
> @@ -266,7 +266,7 @@ int vgic_init(struct kvm *kvm)
>  {
>  	struct vgic_dist *dist = &kvm->arch.vgic;
>  	struct kvm_vcpu *vcpu;
> -	int ret = 0, i;
> +	int ret = 0;
>  
>  	if (vgic_initialized(kvm))
>  		return 0;
> @@ -279,7 +279,7 @@ int vgic_init(struct kvm *kvm)
>  	if (ret)
>  		goto out;
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		kvm_vgic_vcpu_enable(vcpu);
>  
>  	ret = kvm_vgic_setup_default_irq_routing(kvm);
> @@ -327,13 +327,12 @@ void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu)
>  static void __kvm_vgic_destroy(struct kvm *kvm)
>  {
>  	struct kvm_vcpu *vcpu;
> -	int i;
>  
>  	vgic_debug_destroy(kvm);
>  
>  	kvm_vgic_dist_destroy(kvm);
>  
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(vcpu, kvm)
>  		kvm_vgic_vcpu_destroy(vcpu);
>  }
>  
> diff --git a/virt/kvm/arm/vgic/vgic-kvm-device.c b/virt/kvm/arm/vgic/vgic-kvm-device.c
> index c5124737c7fc..3c3e865dc98b 100644
> --- a/virt/kvm/arm/vgic/vgic-kvm-device.c
> +++ b/virt/kvm/arm/vgic/vgic-kvm-device.c
> @@ -257,31 +257,33 @@ int vgic_v2_parse_attr(struct kvm_device *dev, struct kvm_device_attr *attr,
>  	return 0;
>  }
>  
> -/* unlocks vcpus from @vcpu_lock_idx and smaller */
> -static void unlock_vcpus(struct kvm *kvm, int vcpu_lock_idx)
> +/* unlocks vcpus from up to @last_locked */

from up to ?

I think you mean up to and including.

> +static void unlock_vcpus(struct kvm *kvm, struct kvm_vcpu *last_locked)
>  {
> -	struct kvm_vcpu *tmp_vcpu;
> +	if (last_locked) {
> +		struct kvm_vcpu *tmp_vcpu;

That would be more nicely written as 
	if (!last_locked)
		return

	kvm_for_each_vcpu(...)

But why not accept a NULL poiner here and call unlock_vcpus from
unlock_all_vcpus ?

>  
> -	for (; vcpu_lock_idx >= 0; vcpu_lock_idx--) {
> -		tmp_vcpu = kvm_get_vcpu(kvm, vcpu_lock_idx);
> -		mutex_unlock(&tmp_vcpu->mutex);
> +		kvm_for_each_vcpu(tmp_vcpu, kvm) {
> +			mutex_unlock(&tmp_vcpu->mutex);
> +
> +			if (tmp_vcpu == last_locked)
> +				return;
> +		}
>  	}
>  }
>  
>  void unlock_all_vcpus(struct kvm *kvm)
>  {
> -	int i;
>  	struct kvm_vcpu *tmp_vcpu;
>  
> -	kvm_for_each_vcpu(i, tmp_vcpu, kvm)
> +	kvm_for_each_vcpu(tmp_vcpu, kvm)
>  		mutex_unlock(&tmp_vcpu->mutex);
>  }
>  
>  /* Returns true if all vcpus were locked, false otherwise */
>  bool lock_all_vcpus(struct kvm *kvm)
>  {
> -	struct kvm_vcpu *tmp_vcpu;
> -	int c;
> +	struct kvm_vcpu *tmp_vcpu, *last_locked = NULL;
>  
>  	/*
>  	 * Any time a vcpu is run, vcpu_load is called which tries to grab the
> @@ -289,11 +291,13 @@ bool lock_all_vcpus(struct kvm *kvm)
>  	 * that no other VCPUs are run and fiddle with the vgic state while we
>  	 * access it.
>  	 */
> -	kvm_for_each_vcpu(c, tmp_vcpu, kvm) {
> +	kvm_for_each_vcpu(tmp_vcpu, kvm) {
>  		if (!mutex_trylock(&tmp_vcpu->mutex)) {
> -			unlock_vcpus(kvm, c - 1);
> +			unlock_vcpus(kvm, last_locked);

I don't fully understand the split of the patches (which I assume aim
for bisectability) and why unlock_all_vcpus had to be changed in the
previous patch but this call to unlock_vcpus() was allowed to remain
until here?

Thanks,
-Christoffer