Subject: Re: [PATCH v8 7/8] kvmppc: Support reset of secure guest

From: Sukadev Bhattiprolu <[email-masked]>
Date: Tue, 17 Sep 2019 16:27:36 -0700

Bharata B Rao [[email-masked]] wrote:
> Add support for reset of secure guest via a new ioctl KVM_PPC_SVM_OFF.
> This ioctl will be issued by QEMU during reset and includes the
> the following steps:
> 
> - Ask UV to terminate the guest via UV_SVM_TERMINATE ucall
> - Unpin the VPA pages so that they can be migrated back to secure
>   side when guest becomes secure again. This is required because
>   pinned pages can't be migrated.
> - Reinitialize guest's partitioned scoped page tables. These are
>   freed when guest becomes secure (H_SVM_INIT_DONE)
> - Release all device pages of the secure guest.
> 
> After these steps, guest is ready to issue UV_ESM call once again
> to switch to secure mode.
> 
> Signed-off-by: Bharata B Rao <[email-masked]>
> Signed-off-by: Sukadev Bhattiprolu <[email-masked]>
> 	[Implementation of uv_svm_terminate() and its call from
> 	guest shutdown path]
> Signed-off-by: Ram Pai <[email-masked]>
> 	[Unpinning of VPA pages]
> ---
>  Documentation/virt/kvm/api.txt              | 19 ++++++
>  arch/powerpc/include/asm/kvm_book3s_uvmem.h |  7 ++
>  arch/powerpc/include/asm/kvm_ppc.h          |  2 +
>  arch/powerpc/include/asm/ultravisor-api.h   |  1 +
>  arch/powerpc/include/asm/ultravisor.h       |  5 ++
>  arch/powerpc/kvm/book3s_hv.c                | 74 +++++++++++++++++++++
>  arch/powerpc/kvm/book3s_hv_uvmem.c          | 62 ++++++++++++++++-
>  arch/powerpc/kvm/powerpc.c                  | 12 ++++
>  include/uapi/linux/kvm.h                    |  1 +
>  9 files changed, 182 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
> index 2d067767b617..8e7a02e547e9 100644
> --- a/Documentation/virt/kvm/api.txt
> +++ b/Documentation/virt/kvm/api.txt
> @@ -4111,6 +4111,25 @@ Valid values for 'action':
>  #define KVM_PMU_EVENT_ALLOW 0
>  #define KVM_PMU_EVENT_DENY 1
> 
> +4.121 KVM_PPC_SVM_OFF
> +
> +Capability: basic
> +Architectures: powerpc
> +Type: vm ioctl
> +Parameters: none
> +Returns: 0 on successful completion,
> +Errors:
> +  EINVAL:    if ultravisor failed to terminate the secure guest
> +  ENOMEM:    if hypervisor failed to allocate new radix page tables for guest
> +
> +This ioctl is used to turn off the secure mode of the guest or transition
> +the guest from secure mode to normal mode. This is invoked when the guest
> +is reset. This has no effect if called for a normal guest.
> +
> +This ioctl issues an ultravisor call to terminate the secure guest,
> +unpins the VPA pages, reinitializes guest's partition scoped page
> +tables and releases all the device pages that are used to track the
> +secure pages by hypervisor.
> 
>  5. The kvm_run structure
>  ------------------------
> diff --git a/arch/powerpc/include/asm/kvm_book3s_uvmem.h b/arch/powerpc/include/asm/kvm_book3s_uvmem.h
> index fc924ef00b91..6b8cc8edd0ab 100644
> --- a/arch/powerpc/include/asm/kvm_book3s_uvmem.h
> +++ b/arch/powerpc/include/asm/kvm_book3s_uvmem.h
> @@ -13,6 +13,8 @@ unsigned long kvmppc_h_svm_page_out(struct kvm *kvm,
>  				    unsigned long page_shift);
>  unsigned long kvmppc_h_svm_init_start(struct kvm *kvm);
>  unsigned long kvmppc_h_svm_init_done(struct kvm *kvm);
> +void kvmppc_uvmem_free_memslot_pfns(struct kvm *kvm,
> +				    struct kvm_memslots *slots);
>  #else
>  static inline unsigned long
>  kvmppc_h_svm_page_in(struct kvm *kvm, unsigned long gra,
> @@ -37,5 +39,10 @@ static inline unsigned long kvmppc_h_svm_init_done(struct kvm *kvm)
>  {
>  	return H_UNSUPPORTED;
>  }
> +
> +static inline void kvmppc_uvmem_free_memslot_pfns(struct kvm *kvm,
> +						  struct kvm_memslots *slots)
> +{
> +}
>  #endif /* CONFIG_PPC_UV */
>  #endif /* __POWERPC_KVM_PPC_HMM_H__ */
> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
> index 2484e6a8f5ca..e4093d067354 100644
> --- a/arch/powerpc/include/asm/kvm_ppc.h
> +++ b/arch/powerpc/include/asm/kvm_ppc.h
> @@ -177,6 +177,7 @@ extern void kvm_spapr_tce_release_iommu_group(struct kvm *kvm,
>  extern int kvmppc_switch_mmu_to_hpt(struct kvm *kvm);
>  extern int kvmppc_switch_mmu_to_radix(struct kvm *kvm);
>  extern void kvmppc_setup_partition_table(struct kvm *kvm);
> +extern int kvmppc_reinit_partition_table(struct kvm *kvm);
> 
>  extern long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
>  				struct kvm_create_spapr_tce_64 *args);
> @@ -321,6 +322,7 @@ struct kvmppc_ops {
>  			       int size);
>  	int (*store_to_eaddr)(struct kvm_vcpu *vcpu, ulong *eaddr, void *ptr,
>  			      int size);
> +	int (*svm_off)(struct kvm *kvm);
>  };
> 
>  extern struct kvmppc_ops *kvmppc_hv_ops;
> diff --git a/arch/powerpc/include/asm/ultravisor-api.h b/arch/powerpc/include/asm/ultravisor-api.h
> index cf200d4ce703..3a27a0c0be05 100644
> --- a/arch/powerpc/include/asm/ultravisor-api.h
> +++ b/arch/powerpc/include/asm/ultravisor-api.h
> @@ -30,5 +30,6 @@
>  #define UV_PAGE_IN			0xF128
>  #define UV_PAGE_OUT			0xF12C
>  #define UV_PAGE_INVAL			0xF138
> +#define UV_SVM_TERMINATE		0xF13C
> 
>  #endif /* _ASM_POWERPC_ULTRAVISOR_API_H */
> diff --git a/arch/powerpc/include/asm/ultravisor.h b/arch/powerpc/include/asm/ultravisor.h
> index b333241bbe4c..754a37de646d 100644
> --- a/arch/powerpc/include/asm/ultravisor.h
> +++ b/arch/powerpc/include/asm/ultravisor.h
> @@ -62,4 +62,9 @@ static inline int uv_page_inval(u64 lpid, u64 gpa, u64 page_shift)
>  	return ucall_norets(UV_PAGE_INVAL, lpid, gpa, page_shift);
>  }
> 
> +static inline int uv_svm_terminate(u64 lpid)
> +{
> +	return ucall_norets(UV_SVM_TERMINATE, lpid);
> +}
> +
>  #endif	/* _ASM_POWERPC_ULTRAVISOR_H */
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index fc93e5ba5683..b128c3c94135 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -2433,6 +2433,15 @@ static void unpin_vpa(struct kvm *kvm, struct kvmppc_vpa *vpa)
>  					vpa->dirty);
>  }
> 
> +static void unpin_vpa_reset(struct kvm *kvm, struct kvmppc_vpa *vpa)
> +{
> +	unpin_vpa(kvm, vpa);
> +	vpa->gpa = 0;
> +	vpa->pinned_addr = NULL;
> +	vpa->dirty = false;
> +	vpa->update_pending = 0;
> +}
> +
>  static void kvmppc_core_vcpu_free_hv(struct kvm_vcpu *vcpu)
>  {
>  	spin_lock(&vcpu->arch.vpa_update_lock);
> @@ -4593,6 +4602,22 @@ void kvmppc_setup_partition_table(struct kvm *kvm)
>  	kvmhv_set_ptbl_entry(kvm->arch.lpid, dw0, dw1);
>  }
> 
> +/*
> + * Called from KVM_PPC_SVM_OFF ioctl at guest reset time when secure
> + * guest is converted back to normal guest.
> + */
> +int kvmppc_reinit_partition_table(struct kvm *kvm)
> +{
> +	int ret;
> +
> +	ret = kvmppc_init_vm_radix(kvm);
> +	if (ret)
> +		return ret;
> +
> +	kvmppc_setup_partition_table(kvm);
> +	return 0;
> +}
> +
>  /*
>   * Set up HPT (hashed page table) and RMA (real-mode area).
>   * Must be called with kvm->arch.mmu_setup_lock held.
> @@ -4980,6 +5005,7 @@ static void kvmppc_core_destroy_vm_hv(struct kvm *kvm)
>  		if (nesting_enabled(kvm))
>  			kvmhv_release_all_nested(kvm);
>  		kvm->arch.process_table = 0;
> +		uv_svm_terminate(kvm->arch.lpid);
>  		kvmhv_set_ptbl_entry(kvm->arch.lpid, 0, 0);
>  	}
>  	kvmppc_free_lpid(kvm->arch.lpid);
> @@ -5421,6 +5447,53 @@ static int kvmhv_store_to_eaddr(struct kvm_vcpu *vcpu, ulong *eaddr, void *ptr,
>  	return rc;
>  }
> 
> +/*
> + *  IOCTL handler to turn off secure mode of guest
> + *
> + * - Issue ucall to terminate the guest on the UV side
> + * - Unpin the VPA pages (Enables these pages to be migrated back
> + *   when VM becomes secure again)
> + * - Recreate partition table as the guest is transitioning back to
> + *   normal mode
> + * - Release all device pages
> + */
> +static int kvmhv_svm_off(struct kvm *kvm)
> +{
> +	struct kvm_vcpu *vcpu;
> +	int srcu_idx;
> +	int ret = 0;
> +	int i;
> +
> +	if (kvmppc_is_guest_secure(kvm)) {

Nit: Since this entire function only applies to secure guests we could
return here for normal guests.

> +		ret = uv_svm_terminate(kvm->arch.lpid);
> +		if (ret != U_SUCCESS) {
> +			ret = -EINVAL;
> +			goto out;
> +		}
> +
> +		kvm_for_each_vcpu(i, vcpu, kvm) {
> +			spin_lock(&vcpu->arch.vpa_update_lock);
> +			unpin_vpa_reset(kvm, &vcpu->arch.dtl);
> +			unpin_vpa_reset(kvm, &vcpu->arch.slb_shadow);
> +			unpin_vpa_reset(kvm, &vcpu->arch.vpa);
> +			spin_unlock(&vcpu->arch.vpa_update_lock);
> +		}
> +
> +		ret = kvmppc_reinit_partition_table(kvm);
> +		if (ret)
> +			goto out;
> +
> +		srcu_idx = srcu_read_lock(&kvm->srcu);
> +		for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
> +			kvmppc_uvmem_free_memslot_pfns(kvm,
> +			__kvm_memslots(kvm, i));

Nit: fix indentation

> +		srcu_read_unlock(&kvm->srcu, srcu_idx);
> +		kvm->arch.secure_guest = 0;
> +	}
> +out:
> +	return ret;
> +}
> +
>  static struct kvmppc_ops kvm_ops_hv = {
>  	.get_sregs = kvm_arch_vcpu_ioctl_get_sregs_hv,
>  	.set_sregs = kvm_arch_vcpu_ioctl_set_sregs_hv,
> @@ -5463,6 +5536,7 @@ static struct kvmppc_ops kvm_ops_hv = {
>  	.enable_nested = kvmhv_enable_nested,
>  	.load_from_eaddr = kvmhv_load_from_eaddr,
>  	.store_to_eaddr = kvmhv_store_to_eaddr,
> +	.svm_off = kvmhv_svm_off,
>  };
> 
>  static int kvm_init_subcore_bitmap(void)
> diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
> index 6e1da68bbdd5..7caed0338fee 100644
> --- a/arch/powerpc/kvm/book3s_hv_uvmem.c
> +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
> @@ -37,6 +37,7 @@
>  #include <linux/migrate.h>
>  #include <linux/kvm_host.h>
>  #include <asm/ultravisor.h>
> +#include <asm/kvm_ppc.h>
> 
>  static struct dev_pagemap kvmppc_uvmem_pgmap;
>  static unsigned long *kvmppc_uvmem_pfn_bitmap;
> @@ -51,7 +52,7 @@ struct kvmppc_uvmem_page_pvt {
> 
>  bool kvmppc_is_guest_secure(struct kvm *kvm)
>  {
> -	return !!(kvm->arch.secure_guest & KVMPPC_SECURE_INIT_DONE);
> +	return (kvm->arch.secure_guest & KVMPPC_SECURE_INIT_DONE);
>  }

This change could be folded into PATCH 6?
> 
>  unsigned long kvmppc_h_svm_init_start(struct kvm *kvm)
> @@ -85,9 +86,68 @@ unsigned long kvmppc_h_svm_init_done(struct kvm *kvm)
>  		return H_UNSUPPORTED;
> 
>  	kvm->arch.secure_guest |= KVMPPC_SECURE_INIT_DONE;
> +	if (kvm_is_radix(kvm)) {
> +		kvmppc_free_radix(kvm);
> +		pr_info("LPID %d went secure, freed HV side radix pgtables\n",
> +			kvm->arch.lpid);
> +	}
>  	return H_SUCCESS;
>  }
> 
> +/*
> + * Drop device pages that we maintain for the secure guest
> + *
> + * We first mark the pages to be skipped from UV_PAGE_OUT when there
> + * is HV side fault on these pages. Next we *get* these pages, forcing

Is that get page implicit? there is no explicit "get" in this 
function?

> + * fault on them, do fault time migration to replace the device PTEs in
> + * QEMU page table with normal PTEs from newly allocated pages.
> + */
> +static void kvmppc_uvmem_drop_pages(struct kvm_memory_slot *free,
> +				   struct kvm *kvm)
> +{
> +	int i;
> +	struct kvmppc_uvmem_page_pvt *pvt;
> +	unsigned long pfn;
> +
> +	for (i = 0; i < free->npages; i++) {
> +		unsigned long *rmap = &free->arch.rmap[i];
> +		struct page *uvmem_page;
> +
> +		if (kvmppc_rmap_type(rmap) == KVMPPC_RMAP_UVMEM_PFN) {
> +			uvmem_page = pfn_to_page(*rmap &
> +						 ~KVMPPC_RMAP_UVMEM_PFN);
> +			pvt = (struct kvmppc_uvmem_page_pvt *)
> +				uvmem_page->zone_device_data;
> +			pvt->skip_page_out = true;
> +
> +			pfn = gfn_to_pfn(kvm, pvt->gpa >> PAGE_SHIFT);
> +			if (is_error_noslot_pfn(pfn))
> +				continue;
> +			kvm_release_pfn_clean(pfn);
> +		}
> +	}
> +}
> +
> +/*
> + * Called from KVM_PPC_SVM_OFF ioctl when secure guest is reset
> + *
> + * UV has already cleaned up the guest, we release any device pages
> + * that we maintain
> + */
> +void kvmppc_uvmem_free_memslot_pfns(struct kvm *kvm, struct kvm_memslots *slots)
> +{
> +	struct kvm_memory_slot *memslot;
> +	int srcu_idx;
> +
> +	if (!slots)
> +		return;
> +
> +	srcu_idx = srcu_read_lock(&kvm->srcu);
> +	kvm_for_each_memslot(memslot, slots)
> +		kvmppc_uvmem_drop_pages(memslot, kvm);
> +	srcu_read_unlock(&kvm->srcu, srcu_idx);
> +}
> +
>  /*
>   * Get a free device PFN from the pool
>   *
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 3e566c2e6066..3f7393177fba 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -31,6 +31,8 @@
>  #include <asm/hvcall.h>
>  #include <asm/plpar_wrappers.h>
>  #endif
> +#include <asm/ultravisor.h>
> +#include <asm/kvm_host.h>
> 
>  #include "timing.h"
>  #include "irq.h"
> @@ -2410,6 +2412,16 @@ long kvm_arch_vm_ioctl(struct file *filp,
>  			r = -EFAULT;
>  		break;
>  	}
> +	case KVM_PPC_SVM_OFF: {
> +		struct kvm *kvm = filp->private_data;
> +
> +		r = 0;
> +		if (!kvm->arch.kvm_ops->svm_off)
> +			goto out;
> +
> +		r = kvm->arch.kvm_ops->svm_off(kvm);
> +		break;
> +	}
>  	default: {
>  		struct kvm *kvm = filp->private_data;
>  		r = kvm->arch.kvm_ops->arch_vm_ioctl(filp, ioctl, arg);
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 5e3f12d5359e..c2393a347680 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1332,6 +1332,7 @@ struct kvm_s390_ucas_mapping {
>  #define KVM_PPC_GET_CPU_CHAR	  _IOR(KVMIO,  0xb1, struct kvm_ppc_cpu_char)
>  /* Available with KVM_CAP_PMU_EVENT_FILTER */
>  #define KVM_SET_PMU_EVENT_FILTER  _IOW(KVMIO,  0xb2, struct kvm_pmu_event_filter)
> +#define KVM_PPC_SVM_OFF		  _IO(KVMIO,  0xb3)
> 
>  /* ioctl for vm fd */
>  #define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)
> -- 
> 2.21.0