On 1/10/2016 8:32 AM, Christoffer Dall wrote:
> On Sat, Dec 26, 2015 at 01:56:56PM -0800, Mario Smarduch wrote:
>> Enable armv8 enhanced fp/simd context switch. Guest and host registers are
>> only
>> context switched on first access and vcpu put.
>>
>> Signed-off-by: Mario Smarduch <[email protected]>
>> ---
>> arch/arm/kvm/arm.c | 13 +++++++++++--
>> arch/arm64/kernel/asm-offsets.c | 1 +
>> arch/arm64/kvm/hyp/entry.S | 1 +
>> arch/arm64/kvm/hyp/switch.c | 26 ++------------------------
>> 4 files changed, 15 insertions(+), 26 deletions(-)
>>
>> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
>> index b16ed98..633a208 100644
>> --- a/arch/arm/kvm/arm.c
>> +++ b/arch/arm/kvm/arm.c
>> @@ -316,10 +316,19 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>> void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>> {
>> /* If the fp/simd registers are dirty save guest, restore host. */
>> - if (vcpu_vfp_isdirty(vcpu))
>> + if (vcpu_vfp_isdirty(vcpu)) {
>> +
>> vcpu_restore_host_vfp_state(vcpu);
>>
>> - /* Restore host FPEXC trashed in vcpu_load */
>> + /*
>> + * For 32bit guest on arm64 save the guest fpexc register
>> + * in EL2 mode.
>> + */
>> + if (vcpu_guest_is_32bit(vcpu))
>> + vcpu_save_fpexc(vcpu);
>> + }
>> +
>> + /* For arm32 restore host FPEXC trashed in vcpu_load. */
>> vcpu_restore_host_fpexc(vcpu);
>>
>> /*
>> diff --git a/arch/arm64/kernel/asm-offsets.c
>> b/arch/arm64/kernel/asm-offsets.c
>> index 94090a6..d69145c 100644
>> --- a/arch/arm64/kernel/asm-offsets.c
>> +++ b/arch/arm64/kernel/asm-offsets.c
>> @@ -112,6 +112,7 @@ int main(void)
>> DEFINE(VCPU_ESR_EL2, offsetof(struct kvm_vcpu,
>> arch.fault.esr_el2));
>> DEFINE(VCPU_FAR_EL2, offsetof(struct kvm_vcpu,
>> arch.fault.far_el2));
>> DEFINE(VCPU_HPFAR_EL2, offsetof(struct kvm_vcpu,
>> arch.fault.hpfar_el2));
>> + DEFINE(VCPU_CPTR_EL2, offsetof(struct kvm_vcpu,
>> arch.cptr_el2));
>> DEFINE(VCPU_HOST_CONTEXT, offsetof(struct kvm_vcpu,
>> arch.host_cpu_context));
>> #endif
>> #ifdef CONFIG_CPU_PM
>> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
>> index fd0fbe9..ce7e903 100644
>> --- a/arch/arm64/kvm/hyp/entry.S
>> +++ b/arch/arm64/kvm/hyp/entry.S
>> @@ -136,6 +136,7 @@ ENTRY(__fpsimd_guest_restore)
>> isb
>>
>> mrs x3, tpidr_el2
>> + str w2, [x3, #VCPU_CPTR_EL2]
>
> I'm confused here, why do we need to do this now and not in the previous
> patch?
There should be no harm doing it in previous patch, but this patch
activates the lazy switch and I thought this would be a better
place for it.
>
> Maybe it helps if we merge these last two patches into one.
>
>>
>> ldr x0, [x3, #VCPU_HOST_CONTEXT]
>> kern_hyp_va x0
>> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
>> index ca8f5a5..962d179 100644
>> --- a/arch/arm64/kvm/hyp/switch.c
>> +++ b/arch/arm64/kvm/hyp/switch.c
>> @@ -19,24 +19,10 @@
>>
>> static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
>> {
>> - u64 val;
>> -
>> - /*
>> - * We are about to set CPTR_EL2.TFP to trap all floating point
>> - * register accesses to EL2, however, the ARM ARM clearly states that
>> - * traps are only taken to EL2 if the operation would not otherwise
>> - * trap to EL1. Therefore, always make sure that for 32-bit guests,
>> - * we set FPEXC.EN to prevent traps to EL1, when setting the TFP bit.
>> - */
>> - val = vcpu->arch.hcr_el2;
>> - if (!(val & HCR_RW)) {
>> - write_sysreg(1 << 30, fpexc32_el2);
>> - isb();
>> - }
>> - write_sysreg(val, hcr_el2);
>> + write_sysreg(vcpu->arch.hcr_el2, hcr_el2);
>> /* Trap on AArch32 cp15 c15 accesses (EL1 or EL0) */
>> write_sysreg(1 << 15, hstr_el2);
>> - write_sysreg(CPTR_EL2_TTA | CPTR_EL2_TFP, cptr_el2);
>> + write_sysreg(vcpu->arch.cptr_el2, cptr_el2);
>> write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
>> }
>>
>> @@ -89,7 +75,6 @@ static int __hyp_text __guest_run(struct kvm_vcpu *vcpu)
>> {
>> struct kvm_cpu_context *host_ctxt;
>> struct kvm_cpu_context *guest_ctxt;
>> - bool fp_enabled;
>> u64 exit_code;
>>
>> vcpu = kern_hyp_va(vcpu);
>> @@ -119,8 +104,6 @@ static int __hyp_text __guest_run(struct kvm_vcpu *vcpu)
>> exit_code = __guest_enter(vcpu, host_ctxt);
>> /* And we're baaack! */
>>
>> - fp_enabled = __fpsimd_enabled();
>> -
>> __sysreg_save_state(guest_ctxt);
>> __sysreg32_save_state(vcpu);
>> __timer_save_state(vcpu);
>> @@ -131,11 +114,6 @@ static int __hyp_text __guest_run(struct kvm_vcpu *vcpu)
>>
>> __sysreg_restore_state(host_ctxt);
>>
>> - if (fp_enabled) {
>> - __fpsimd_save_state(&guest_ctxt->gp_regs.fp_regs);
>> - __fpsimd_restore_state(&host_ctxt->gp_regs.fp_regs);
>> - }
>> -
>
> why do we remove this logic here but preserve something in
> __sysreg32_save_state() ?
Missed it, fpexec code should be removed, that's taken care of
in vcpu_put which stores it to same memory. Thanks for spotting it.
>
>
>
>> __debug_save_state(vcpu, kern_hyp_va(vcpu->arch.debug_ptr), guest_ctxt);
>> __debug_cond_restore_host_state(vcpu);
>>
>> --
>> 1.9.1
>>
> Thanks,
> -Christoffer
>
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