On Mon, Jan 11, 2016 at 04:51:58PM -0800, Mario Smarduch wrote:
>
>
> 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 <m.smarduch@xxxxxxxxxxx>
> >> ---
> >> 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.
>
ok, thanks,
-Christoffer
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