| Message ID | 1473093097-30932-8-git-send-email-punit.agrawal@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Sep 05, 2016 at 05:31:37PM +0100, Punit Agrawal wrote: > The TTLB bit of Hypervisor Control Register (HCR_EL2) controls the > trapping of guest TLB maintenance instructions. Taking the trap requires > a switch to the hypervisor and is an expensive operation. > > Enable selective trapping of guest TLB instructions when the associated > perf trace event is enabled for a specific virtual machine. > > Signed-off-by: Punit Agrawal <punit.agrawal@arm.com> > Cc: Christoffer Dall <christoffer.dall@linaro.org> > Cc: Marc Zyngier <marc.zyngier@arm.com> > --- > arch/arm64/kvm/perf_trace.c | 32 ++++++++++++++++++++++++++++++++ > 1 file changed, 32 insertions(+) > > diff --git a/arch/arm64/kvm/perf_trace.c b/arch/arm64/kvm/perf_trace.c > index 8bacd18..f26da1d 100644 > --- a/arch/arm64/kvm/perf_trace.c > +++ b/arch/arm64/kvm/perf_trace.c > @@ -17,6 +17,8 @@ > #include <linux/kvm_host.h> > #include <linux/trace_events.h> > > +#include <asm/kvm_emulate.h> > + > typedef int (*perf_trace_callback_fn)(struct kvm *kvm, bool enable); > > struct kvm_trace_hook { > @@ -24,7 +26,37 @@ struct kvm_trace_hook { > perf_trace_callback_fn setup_fn; > }; > > +static int tlb_invalidate_trap(struct kvm *kvm, bool enable) > +{ > + int i; > + struct kvm_vcpu *vcpu; > + > + /* > + * Halt the VM to ensure atomic update across all vcpus (this > + * avoids racy behaviour against other modifications of > + * HCR_EL2 such as kvm_toggle_cache/kvm_set_way_flush). > + */ > + kvm_arm_halt_guest(kvm); > + kvm_for_each_vcpu(i, vcpu, kvm) { > + unsigned long hcr = vcpu_get_hcr(vcpu); > + > + if (enable) > + hcr |= HCR_TTLB; > + else > + hcr &= ~HCR_TTLB; > + > + vcpu_set_hcr(vcpu, hcr); > + } > + kvm_arm_resume_guest(kvm); > + > + return 0; > +} > + > static struct kvm_trace_hook trace_hook[] = { > + { > + .key = "kvm_tlb_invalidate", is this key defined elsewhere? If not, I think the name is ambiguous, because it's unclear if this means 'kvm the subsystem' or 'a kvm guest', by looking purely at the string. > + .setup_fn = tlb_invalidate_trap, > + }, > { }, > }; > > -- > 2.8.1 > Otherwise looks ok to me. -Christoffer
Christoffer Dall <christoffer.dall@linaro.org> writes: > On Mon, Sep 05, 2016 at 05:31:37PM +0100, Punit Agrawal wrote: >> The TTLB bit of Hypervisor Control Register (HCR_EL2) controls the >> trapping of guest TLB maintenance instructions. Taking the trap requires >> a switch to the hypervisor and is an expensive operation. >> >> Enable selective trapping of guest TLB instructions when the associated >> perf trace event is enabled for a specific virtual machine. >> >> Signed-off-by: Punit Agrawal <punit.agrawal@arm.com> >> Cc: Christoffer Dall <christoffer.dall@linaro.org> >> Cc: Marc Zyngier <marc.zyngier@arm.com> >> --- >> arch/arm64/kvm/perf_trace.c | 32 ++++++++++++++++++++++++++++++++ >> 1 file changed, 32 insertions(+) >> >> diff --git a/arch/arm64/kvm/perf_trace.c b/arch/arm64/kvm/perf_trace.c >> index 8bacd18..f26da1d 100644 >> --- a/arch/arm64/kvm/perf_trace.c >> +++ b/arch/arm64/kvm/perf_trace.c >> @@ -17,6 +17,8 @@ >> #include <linux/kvm_host.h> >> #include <linux/trace_events.h> >> >> +#include <asm/kvm_emulate.h> >> + >> typedef int (*perf_trace_callback_fn)(struct kvm *kvm, bool enable); >> >> struct kvm_trace_hook { >> @@ -24,7 +26,37 @@ struct kvm_trace_hook { >> perf_trace_callback_fn setup_fn; >> }; >> >> +static int tlb_invalidate_trap(struct kvm *kvm, bool enable) >> +{ >> + int i; >> + struct kvm_vcpu *vcpu; >> + >> + /* >> + * Halt the VM to ensure atomic update across all vcpus (this >> + * avoids racy behaviour against other modifications of >> + * HCR_EL2 such as kvm_toggle_cache/kvm_set_way_flush). >> + */ >> + kvm_arm_halt_guest(kvm); >> + kvm_for_each_vcpu(i, vcpu, kvm) { >> + unsigned long hcr = vcpu_get_hcr(vcpu); >> + >> + if (enable) >> + hcr |= HCR_TTLB; >> + else >> + hcr &= ~HCR_TTLB; >> + >> + vcpu_set_hcr(vcpu, hcr); >> + } >> + kvm_arm_resume_guest(kvm); >> + >> + return 0; >> +} >> + >> static struct kvm_trace_hook trace_hook[] = { >> + { >> + .key = "kvm_tlb_invalidate", > > is this key defined elsewhere? If not, I think the name is ambiguous, > because it's unclear if this means 'kvm the subsystem' or 'a kvm guest', > by looking purely at the string. The key is the name of the tracepoint that the callback is executed against. Here it is the tracepoint defined in Patch 6/7. I've now added a comment to the definition of "struct kvm_trace_hook" to explain what the key is. > >> + .setup_fn = tlb_invalidate_trap, >> + }, >> { }, >> }; >> >> -- >> 2.8.1 >> > > Otherwise looks ok to me. > > -Christoffer > _______________________________________________ > kvmarm mailing list > kvmarm@lists.cs.columbia.edu > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
diff --git a/arch/arm64/kvm/perf_trace.c b/arch/arm64/kvm/perf_trace.c index 8bacd18..f26da1d 100644 --- a/arch/arm64/kvm/perf_trace.c +++ b/arch/arm64/kvm/perf_trace.c @@ -17,6 +17,8 @@ #include <linux/kvm_host.h> #include <linux/trace_events.h> +#include <asm/kvm_emulate.h> + typedef int (*perf_trace_callback_fn)(struct kvm *kvm, bool enable); struct kvm_trace_hook { @@ -24,7 +26,37 @@ struct kvm_trace_hook { perf_trace_callback_fn setup_fn; }; +static int tlb_invalidate_trap(struct kvm *kvm, bool enable) +{ + int i; + struct kvm_vcpu *vcpu; + + /* + * Halt the VM to ensure atomic update across all vcpus (this + * avoids racy behaviour against other modifications of + * HCR_EL2 such as kvm_toggle_cache/kvm_set_way_flush). + */ + kvm_arm_halt_guest(kvm); + kvm_for_each_vcpu(i, vcpu, kvm) { + unsigned long hcr = vcpu_get_hcr(vcpu); + + if (enable) + hcr |= HCR_TTLB; + else + hcr &= ~HCR_TTLB; + + vcpu_set_hcr(vcpu, hcr); + } + kvm_arm_resume_guest(kvm); + + return 0; +} + static struct kvm_trace_hook trace_hook[] = { + { + .key = "kvm_tlb_invalidate", + .setup_fn = tlb_invalidate_trap, + }, { }, };
The TTLB bit of Hypervisor Control Register (HCR_EL2) controls the trapping of guest TLB maintenance instructions. Taking the trap requires a switch to the hypervisor and is an expensive operation. Enable selective trapping of guest TLB instructions when the associated perf trace event is enabled for a specific virtual machine. Signed-off-by: Punit Agrawal <punit.agrawal@arm.com> Cc: Christoffer Dall <christoffer.dall@linaro.org> Cc: Marc Zyngier <marc.zyngier@arm.com> --- arch/arm64/kvm/perf_trace.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+)