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?
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() ?
> __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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