On Wed, Jun 24, 2015 at 05:04:11PM -0700, Mario Smarduch wrote: > This patch only saves and restores FP/SIMD registers on Guest access. To do > this cptr_el2 FP/SIMD trap is set on Guest entry and later checked on exit. > lmbench, hackbench show significant improvements, for 30-50% exits FP/SIMD > context is not saved/restored > > Signed-off-by: Mario Smarduch <m.smarduch@xxxxxxxxxxx> > --- > arch/arm64/include/asm/kvm_arm.h | 5 ++++- > arch/arm64/kvm/hyp.S | 46 +++++++++++++++++++++++++++++++++++--- > 2 files changed, 47 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h > index ac6fafb..7605e09 100644 > --- a/arch/arm64/include/asm/kvm_arm.h > +++ b/arch/arm64/include/asm/kvm_arm.h > @@ -171,10 +171,13 @@ > #define HSTR_EL2_TTEE (1 << 16) > #define HSTR_EL2_T(x) (1 << x) > > +/* Hyp Coproccessor Trap Register Shifts */ > +#define CPTR_EL2_TFP_SHIFT 10 > + > /* Hyp Coprocessor Trap Register */ > #define CPTR_EL2_TCPAC (1 << 31) > #define CPTR_EL2_TTA (1 << 20) > -#define CPTR_EL2_TFP (1 << 10) > +#define CPTR_EL2_TFP (1 << CPTR_EL2_TFP_SHIFT) > > /* Hyp Debug Configuration Register bits */ > #define MDCR_EL2_TDRA (1 << 11) > diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S > index 5befd01..de0788f 100644 > --- a/arch/arm64/kvm/hyp.S > +++ b/arch/arm64/kvm/hyp.S > @@ -673,6 +673,15 @@ > tbz \tmp, #KVM_ARM64_DEBUG_DIRTY_SHIFT, \target > .endm > > +/* > + * Check cptr VFP/SIMD accessed bit, if set VFP/SIMD not accessed by guest. This comment doesn't really help me understand the function, may I suggest: Branch to target if CPTR_EL2.TFP bit is set (VFP/SIMD trapping enabled) > + */ > +.macro skip_fpsimd_state tmp, target > + mrs \tmp, cptr_el2 > + tbnz \tmp, #CPTR_EL2_TFP_SHIFT, \target > +.endm > + > + > .macro compute_debug_state target > // Compute debug state: If any of KDE, MDE or KVM_ARM64_DEBUG_DIRTY > // is set, we do a full save/restore cycle and disable trapping. > @@ -763,6 +772,7 @@ > ldr x2, [x0, #VCPU_HCR_EL2] > msr hcr_el2, x2 > mov x2, #CPTR_EL2_TTA > + orr x2, x2, #CPTR_EL2_TFP > msr cptr_el2, x2 > > mov x2, #(1 << 15) // Trap CP15 Cr=15 > @@ -785,7 +795,6 @@ > .macro deactivate_traps > mov x2, #HCR_RW > msr hcr_el2, x2 > - msr cptr_el2, xzr > msr hstr_el2, xzr > > mrs x2, mdcr_el2 > @@ -912,6 +921,28 @@ __restore_fpsimd: > restore_fpsimd > ret > > +switch_to_guest_fpsimd: > + push x4, lr > + > + mrs x2, cptr_el2 > + bic x2, x2, #CPTR_EL2_TFP > + msr cptr_el2, x2 > + > + mrs x0, tpidr_el2 > + > + ldr x2, [x0, #VCPU_HOST_CONTEXT] > + kern_hyp_va x2 > + bl __save_fpsimd > + > + add x2, x0, #VCPU_CONTEXT > + bl __restore_fpsimd > + > + pop x4, lr > + pop x2, x3 > + pop x0, x1 > + > + eret > + > /* > * u64 __kvm_vcpu_run(struct kvm_vcpu *vcpu); > * > @@ -932,7 +963,6 @@ ENTRY(__kvm_vcpu_run) > kern_hyp_va x2 > > save_host_regs > - bl __save_fpsimd > bl __save_sysregs > > compute_debug_state 1f > @@ -948,7 +978,6 @@ ENTRY(__kvm_vcpu_run) > add x2, x0, #VCPU_CONTEXT > > bl __restore_sysregs > - bl __restore_fpsimd > > skip_debug_state x3, 1f > bl __restore_debug > @@ -967,7 +996,9 @@ __kvm_vcpu_return: > add x2, x0, #VCPU_CONTEXT > > save_guest_regs > + skip_fpsimd_state x3, 1f > bl __save_fpsimd > +1: > bl __save_sysregs > > skip_debug_state x3, 1f > @@ -986,7 +1017,11 @@ __kvm_vcpu_return: > kern_hyp_va x2 > > bl __restore_sysregs > + skip_fpsimd_state x3, 1f > bl __restore_fpsimd > +1: > + /* Clear FPSIMD and Trace trapping */ > + msr cptr_el2, xzr why not simply move the deactivate_traps down here instead? > > skip_debug_state x3, 1f > // Clear the dirty flag for the next run, as all the state has > @@ -1201,6 +1236,11 @@ el1_trap: > * x1: ESR > * x2: ESR_EC > */ > + > + /* Guest accessed VFP/SIMD registers, save host, restore Guest */ > + cmp x2, #ESR_ELx_EC_FP_ASIMD > + b.eq switch_to_guest_fpsimd > + > cmp x2, #ESR_ELx_EC_DABT_LOW > mov x0, #ESR_ELx_EC_IABT_LOW > ccmp x2, x0, #4, ne > -- > 1.7.9.5 > Otherwise looks good, -Christoffer -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
