Subject: [PATCH v5 01/19] arm/arm64: KVM: rework MPIDR assignment and add accessors

From: [email-masked] (Andre Przywara)
Date: Mon, 08 Dec 2014 15:26:09 +0000

Hi Mark,

On 08/12/14 15:06, Mark Rutland wrote:
> Hi Andre,
> 
> On Mon, Dec 08, 2014 at 12:37:36PM +0000, Andre Przywara wrote:
>> The virtual MPIDR registers (containing topology information) for the
>> guest are currently mapped linearily to the vcpu_id. Improve this
>> mapping for arm64 by using three levels to not artificially limit the
>> number of vCPUs.
> 
> For AArch64, there are four levels in the MPIDR_EL1, Aff{3,2,1,0}, and
> all four are covered by MPIDR_HWID_BITMASK.
> 
> The code below only seems to handle Aff{2,1,0}. Is the vCPU limited at
> creation time such that Aff3 is always zero?

Yes. The GICv3 has a bit to optionally drop Aff3 support from it's own
CPU addressing scheme, which we use to avoid "real" 64-bit register
accesses [1].
So by definition we don't use Aff3 for the VCPUs, which limits our
number of VCPUs to 2**20 (8+8+4), which isn't really a limit right now.
Other parts of the code only allow 255 VCPUs at the moment.

Cheers,
Andre.

[1]
http://www.linux-arm.org/git?p=linux-ap.git;a=blob;f=virt/kvm/arm/vgic-v3-emul.c;h=18af188e8c64da5ed21291f8b7da02cd7aed07c4;hb=8bcfd318e0edabbf9aafa8512af0b56507495661#l261

>> To help this, change and rename the kvm_vcpu_get_mpidr() function to
>> mask off the non-affinity bits in the MPIDR register.
>> Also add an accessor to later allow easier access to a vCPU with a
>> given MPIDR. Use this new accessor in the PSCI emulation.
>>
>> Signed-off-by: Andre Przywara <[email-masked]>
>> Reviewed-by: Christoffer Dall <[email-masked]>
>> ---
>> Changelog v4...v5:
>>  (add Reviewed-by:)
>>
>> Changelog v3...v4:
>> - rename kvm_vcpu_get_mpidr() to kvm_vcpu_get_mpidr_aff()
>> - simplify kvm_mpidr_to_vcpu()
>> - fixup comment
>>
>>  arch/arm/include/asm/kvm_emulate.h   |    5 +++--
>>  arch/arm/include/asm/kvm_host.h      |    2 ++
>>  arch/arm/kvm/arm.c                   |   13 +++++++++++++
>>  arch/arm/kvm/psci.c                  |   17 +++++------------
>>  arch/arm64/include/asm/kvm_emulate.h |    5 +++--
>>  arch/arm64/include/asm/kvm_host.h    |    2 ++
>>  arch/arm64/kvm/sys_regs.c            |   13 +++++++++++--
>>  7 files changed, 39 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
>> index b9db269..3ae88ac 100644
>> --- a/arch/arm/include/asm/kvm_emulate.h
>> +++ b/arch/arm/include/asm/kvm_emulate.h
>> @@ -23,6 +23,7 @@
>>  #include <asm/kvm_asm.h>
>>  #include <asm/kvm_mmio.h>
>>  #include <asm/kvm_arm.h>
>> +#include <asm/cputype.h>
>>  
>>  unsigned long *vcpu_reg(struct kvm_vcpu *vcpu, u8 reg_num);
>>  unsigned long *vcpu_spsr(struct kvm_vcpu *vcpu);
>> @@ -162,9 +163,9 @@ static inline u32 kvm_vcpu_hvc_get_imm(struct kvm_vcpu *vcpu)
>>  	return kvm_vcpu_get_hsr(vcpu) & HSR_HVC_IMM_MASK;
>>  }
>>  
>> -static inline unsigned long kvm_vcpu_get_mpidr(struct kvm_vcpu *vcpu)
>> +static inline unsigned long kvm_vcpu_get_mpidr_aff(struct kvm_vcpu *vcpu)
>>  {
>> -	return vcpu->arch.cp15[c0_MPIDR];
>> +	return vcpu->arch.cp15[c0_MPIDR] & MPIDR_HWID_BITMASK;
>>  }
>>  
>>  static inline void kvm_vcpu_set_be(struct kvm_vcpu *vcpu)
>> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
>> index 53036e2..b443dfe 100644
>> --- a/arch/arm/include/asm/kvm_host.h
>> +++ b/arch/arm/include/asm/kvm_host.h
>> @@ -236,6 +236,8 @@ static inline void vgic_arch_setup(const struct vgic_params *vgic)
>>  int kvm_perf_init(void);
>>  int kvm_perf_teardown(void);
>>  
>> +struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
>> +
>>  static inline void kvm_arch_hardware_disable(void) {}
>>  static inline void kvm_arch_hardware_unsetup(void) {}
>>  static inline void kvm_arch_sync_events(struct kvm *kvm) {}
>> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
>> index 9e193c8..c2a5c69 100644
>> --- a/arch/arm/kvm/arm.c
>> +++ b/arch/arm/kvm/arm.c
>> @@ -977,6 +977,19 @@ static void check_kvm_target_cpu(void *ret)
>>  	*(int *)ret = kvm_target_cpu();
>>  }
>>  
>> +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) {
>> +		if (mpidr == kvm_vcpu_get_mpidr_aff(vcpu))
>> +			return vcpu;
>> +	}
>> +	return NULL;
>> +}
>> +
>>  /**
>>   * Initialize Hyp-mode and memory mappings on all CPUs.
>>   */
>> diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
>> index 09cf377..84121b2 100644
>> --- a/arch/arm/kvm/psci.c
>> +++ b/arch/arm/kvm/psci.c
>> @@ -21,6 +21,7 @@
>>  #include <asm/cputype.h>
>>  #include <asm/kvm_emulate.h>
>>  #include <asm/kvm_psci.h>
>> +#include <asm/kvm_host.h>
>>  
>>  /*
>>   * This is an implementation of the Power State Coordination Interface
>> @@ -65,25 +66,17 @@ static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
>>  static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
>>  {
>>  	struct kvm *kvm = source_vcpu->kvm;
>> -	struct kvm_vcpu *vcpu = NULL, *tmp;
>> +	struct kvm_vcpu *vcpu = NULL;
>>  	wait_queue_head_t *wq;
>>  	unsigned long cpu_id;
>>  	unsigned long context_id;
>> -	unsigned long mpidr;
>>  	phys_addr_t target_pc;
>> -	int i;
>>  
>> -	cpu_id = *vcpu_reg(source_vcpu, 1);
>> +	cpu_id = *vcpu_reg(source_vcpu, 1) & MPIDR_HWID_BITMASK;
>>  	if (vcpu_mode_is_32bit(source_vcpu))
>>  		cpu_id &= ~((u32) 0);
>>  
>> -	kvm_for_each_vcpu(i, tmp, kvm) {
>> -		mpidr = kvm_vcpu_get_mpidr(tmp);
>> -		if ((mpidr & MPIDR_HWID_BITMASK) == (cpu_id & MPIDR_HWID_BITMASK)) {
>> -			vcpu = tmp;
>> -			break;
>> -		}
>> -	}
>> +	vcpu = kvm_mpidr_to_vcpu(kvm, cpu_id);
>>  
>>  	/*
>>  	 * Make sure the caller requested a valid CPU and that the CPU is
>> @@ -154,7 +147,7 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
>>  	 * then ON else OFF
>>  	 */
>>  	kvm_for_each_vcpu(i, tmp, kvm) {
>> -		mpidr = kvm_vcpu_get_mpidr(tmp);
>> +		mpidr = kvm_vcpu_get_mpidr_aff(tmp);
>>  		if (((mpidr & target_affinity_mask) == target_affinity) &&
>>  		    !tmp->arch.pause) {
>>  			return PSCI_0_2_AFFINITY_LEVEL_ON;
>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>> index 5674a55..d4daaa5 100644
>> --- a/arch/arm64/include/asm/kvm_emulate.h
>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>> @@ -27,6 +27,7 @@
>>  #include <asm/kvm_arm.h>
>>  #include <asm/kvm_mmio.h>
>>  #include <asm/ptrace.h>
>> +#include <asm/cputype.h>
>>  
>>  unsigned long *vcpu_reg32(const struct kvm_vcpu *vcpu, u8 reg_num);
>>  unsigned long *vcpu_spsr32(const struct kvm_vcpu *vcpu);
>> @@ -182,9 +183,9 @@ static inline u8 kvm_vcpu_trap_get_fault_type(const struct kvm_vcpu *vcpu)
>>  	return kvm_vcpu_get_hsr(vcpu) & ESR_EL2_FSC_TYPE;
>>  }
>>  
>> -static inline unsigned long kvm_vcpu_get_mpidr(struct kvm_vcpu *vcpu)
>> +static inline unsigned long kvm_vcpu_get_mpidr_aff(struct kvm_vcpu *vcpu)
>>  {
>> -	return vcpu_sys_reg(vcpu, MPIDR_EL1);
>> +	return vcpu_sys_reg(vcpu, MPIDR_EL1) & MPIDR_HWID_BITMASK;
>>  }
>>  
>>  static inline void kvm_vcpu_set_be(struct kvm_vcpu *vcpu)
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 2012c4b..286bb61 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -207,6 +207,8 @@ int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
>>  int kvm_perf_init(void);
>>  int kvm_perf_teardown(void);
>>  
>> +struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
>> +
>>  static inline void __cpu_init_hyp_mode(phys_addr_t boot_pgd_ptr,
>>  				       phys_addr_t pgd_ptr,
>>  				       unsigned long hyp_stack_ptr,
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index 3d7c2df..136e679 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -252,10 +252,19 @@ static void reset_amair_el1(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
>>  
>>  static void reset_mpidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
>>  {
>> +	u64 mpidr;
>> +
>>  	/*
>> -	 * Simply map the vcpu_id into the Aff0 field of the MPIDR.
>> +	 * Map the vcpu_id into the first three affinity level fields of
>> +	 * the MPIDR. We limit the number of VCPUs in level 0 due to a
>> +	 * limitation to 16 CPUs in that level in the ICC_SGIxR registers
>> +	 * of the GICv3 to be able to address each CPU directly when
>> +	 * sending IPIs.
>>  	 */
>> -	vcpu_sys_reg(vcpu, MPIDR_EL1) = (1UL << 31) | (vcpu->vcpu_id & 0xff);
>> +	mpidr = (vcpu->vcpu_id & 0x0f) << MPIDR_LEVEL_SHIFT(0);
>> +	mpidr |= ((vcpu->vcpu_id >> 4) & 0xff) << MPIDR_LEVEL_SHIFT(1);
>> +	mpidr |= ((vcpu->vcpu_id >> 12) & 0xff) << MPIDR_LEVEL_SHIFT(2);
>> +	vcpu_sys_reg(vcpu, MPIDR_EL1) = (1ULL << 31) | mpidr;
>>  }
>>  
>>  /* Silly macro to expand the DBG{BCR,BVR,WVR,WCR}n_EL1 registers in one go */
>> -- 
>> 1.7.9.5
>>
>>
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