On Fri, Oct 30, 2015 at 02:56:33PM -0700, Mario Smarduch wrote:
> This patch enables arm64 lazy fp/simd switch, similar to arm described in
> second patch. Change from previous version - restore function is moved to
> host.
>
> Signed-off-by: Mario Smarduch <m.smarduch@xxxxxxxxxxx>
> ---
> arch/arm64/include/asm/kvm_host.h | 2 +-
> arch/arm64/kernel/asm-offsets.c | 1 +
> arch/arm64/kvm/hyp.S | 37 +++++++++++++++++++++++++++++++------
> 3 files changed, 33 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 26a2347..dcecf92 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -251,11 +251,11 @@ static inline void kvm_arch_hardware_unsetup(void) {}
> static inline void kvm_arch_sync_events(struct kvm *kvm) {}
> static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
> static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
> -static inline void kvm_restore_host_vfp_state(struct kvm_vcpu *vcpu) {}
>
> void kvm_arm_init_debug(void);
> void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
> void kvm_arm_clear_debug(struct kvm_vcpu *vcpu);
> void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu);
> +void kvm_restore_host_vfp_state(struct kvm_vcpu *vcpu);
>
> #endif /* __ARM64_KVM_HOST_H__ */
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index 8d89cf8..c9c5242 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -124,6 +124,7 @@ int main(void)
> DEFINE(VCPU_HCR_EL2, offsetof(struct kvm_vcpu, arch.hcr_el2));
> DEFINE(VCPU_MDCR_EL2, offsetof(struct kvm_vcpu, arch.mdcr_el2));
> DEFINE(VCPU_IRQ_LINES, offsetof(struct kvm_vcpu, arch.irq_lines));
> + DEFINE(VCPU_VFP_DIRTY, offsetof(struct kvm_vcpu, arch.vfp_dirty));
> DEFINE(VCPU_HOST_CONTEXT, offsetof(struct kvm_vcpu, arch.host_cpu_context));
> DEFINE(VCPU_HOST_DEBUG_STATE, offsetof(struct kvm_vcpu, arch.host_debug_state));
> DEFINE(VCPU_TIMER_CNTV_CTL, offsetof(struct kvm_vcpu, arch.timer_cpu.cntv_ctl));
> diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
> index e583613..ed2c4cf 100644
> --- a/arch/arm64/kvm/hyp.S
> +++ b/arch/arm64/kvm/hyp.S
> @@ -36,6 +36,28 @@
> #define CPU_SYSREG_OFFSET(x) (CPU_SYSREGS + 8*x)
>
> .text
> +
> +/**
> + * void kvm_restore_host_vfp_state(struct vcpu *vcpu) - Executes lazy
> + * fp/simd switch, saves the guest, restores host. Called from host
> + * mode, placed outside of hyp section.
same comments on style as previous patch
> + */
> +ENTRY(kvm_restore_host_vfp_state)
> + push xzr, lr
> +
> + add x2, x0, #VCPU_CONTEXT
> + mov w3, #0
> + strb w3, [x0, #VCPU_VFP_DIRTY]
I've been discussing with myself if it would make more sense to clear
the dirty flag in the C-code...
> +
> + bl __save_fpsimd
> +
> + ldr x2, [x0, #VCPU_HOST_CONTEXT]
> + bl __restore_fpsimd
> +
> + pop xzr, lr
> + ret
> +ENDPROC(kvm_restore_host_vfp_state)
> +
> .pushsection .hyp.text, "ax"
> .align PAGE_SHIFT
>
> @@ -482,7 +504,11 @@
> 99:
> msr hcr_el2, x2
> mov x2, #CPTR_EL2_TTA
> +
> + ldrb w3, [x0, #VCPU_VFP_DIRTY]
> + tbnz w3, #0, 98f
> orr x2, x2, #CPTR_EL2_TFP
> +98:
mmm, don't you need to only set the fpexc32 when you're actually going
to trap the guest accesses?
also, you can consider only setting this in vcpu_load (jumping quickly
to EL2 to do so) if we're running a 32-bit guest. Probably worth
measuring the difference between the extra EL2 jump on vcpu_load
compared to hitting this register on every entry/exit.
Code-wise, it will be nicer to do it on vcpu_load.
> msr cptr_el2, x2
>
> mov x2, #(1 << 15) // Trap CP15 Cr=15
> @@ -669,14 +695,12 @@ __restore_debug:
> ret
>
> __save_fpsimd:
> - skip_fpsimd_state x3, 1f
> save_fpsimd
> -1: ret
> + ret
>
> __restore_fpsimd:
> - skip_fpsimd_state x3, 1f
> restore_fpsimd
> -1: ret
> + ret
>
> switch_to_guest_fpsimd:
> push x4, lr
> @@ -688,6 +712,9 @@ switch_to_guest_fpsimd:
>
> mrs x0, tpidr_el2
>
> + mov w2, #1
> + strb w2, [x0, #VCPU_VFP_DIRTY]
hmm, just noticing this. Are you not writing a 32-bit value to a
potentially 8-bit field (ignoring padding in the struct), as the dirty
flag is declared a bool.
Are you also doing this on the 32-bit side?
> +
> ldr x2, [x0, #VCPU_HOST_CONTEXT]
> kern_hyp_va x2
> bl __save_fpsimd
> @@ -763,7 +790,6 @@ __kvm_vcpu_return:
> add x2, x0, #VCPU_CONTEXT
>
> save_guest_regs
> - bl __save_fpsimd
> bl __save_sysregs
>
> skip_debug_state x3, 1f
> @@ -784,7 +810,6 @@ __kvm_vcpu_return:
> kern_hyp_va x2
>
> bl __restore_sysregs
> - bl __restore_fpsimd
> /* Clear FPSIMD and Trace trapping */
> msr cptr_el2, xzr
>
> --
> 1.9.1
>
Thanks,
-Christoffer
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