On 19 February 2015 at 13:40, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: > On 19/02/15 10:54, Ard Biesheuvel wrote: >> --- >> arch/arm/kvm/mmu.c | 2 +- >> arch/arm64/include/asm/kvm_arm.h | 2 +- >> 2 files changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c >> index 136662547ca6..fa8ec55220ea 100644 >> --- a/arch/arm/kvm/mmu.c >> +++ b/arch/arm/kvm/mmu.c >> @@ -1530,7 +1530,7 @@ void kvm_toggle_cache(struct kvm_vcpu *vcpu, bool was_enabled) >> stage2_flush_vm(vcpu->kvm); >> >> /* Caches are now on, stop trapping VM ops (until a S/W op) */ >> - if (now_enabled) >> + if (0)//now_enabled) >> vcpu_set_hcr(vcpu, vcpu_get_hcr(vcpu) & ~HCR_TVM); >> >> trace_kvm_toggle_cache(*vcpu_pc(vcpu), was_enabled, now_enabled); >> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h >> index 8afb863f5a9e..437e1ec17539 100644 >> --- a/arch/arm64/include/asm/kvm_arm.h >> +++ b/arch/arm64/include/asm/kvm_arm.h >> @@ -75,7 +75,7 @@ >> * FMO: Override CPSR.F and enable signaling with VF >> * SWIO: Turn set/way invalidates into set/way clean+invalidate >> */ >> -#define HCR_GUEST_FLAGS (HCR_TSC | HCR_TSW | HCR_TWE | HCR_TWI | HCR_VM | \ >> +#define HCR_GUEST_FLAGS (HCR_TSC | /* HCR_TSW | */ HCR_TWE | HCR_TWI | HCR_VM | \ > > Why do we stop to trap S/W ops here? We can't let the guest issue those > without doing anything, as this will break anything that expects the > data to make it to memory. Think of the 32bit kernel decompressor, for > example. > TBH patch #3 is just a q'n'd hack to ensure that the TVM bit remains set in HCR. I was assuming that cleaning the entire cache on mmu enable/disable would be sufficient to quantify the performance impact and check whether patch #2 works as advertised. I was wondering: isn't calling stage2_flush_vm() for each set of each way very costly? -- 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
