Messages in this thread | | | Date | Fri, 29 Sep 2023 11:17:49 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH v1 3/5] arm64: KVM: Add interface to set guest value for TRFCR register |
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On Thu, 28 Sep 2023 16:16:07 +0100, James Clark <james.clark@arm.com> wrote: > > Add an interface for the Coresight driver to use to set the value of the > TRFCR register for the guest. This register controls the exclude > settings for trace at different exception levels, and is used to > honor the exclude_host and exclude_guest parameters from the Perf > session. This will be used to later write TRFCR_EL1 on nVHE at guest > switch. For VHE, TRFCR_EL1 is written immediately. Because guest writes > to the register are trapped, the value will persist and can't be > modified. > > The settings must be copied to the vCPU before each run in the same > way that PMU events are because the per-cpu struct isn't accessible in > protected mode. > > Now that both guest and host values are saved, rename trfcr_el1 to > host_trfcr_el1 to make it clear that's the value that should be restored > on return to the host. > > Reviewed-by: Mark Brown <broonie@kernel.org> (sysreg) > Signed-off-by: James Clark <james.clark@arm.com> > --- > arch/arm64/include/asm/kvm_host.h | 6 +++++- > arch/arm64/kvm/arm.c | 1 + > arch/arm64/kvm/debug.c | 21 +++++++++++++++++++++ > arch/arm64/kvm/hyp/nvhe/debug-sr.c | 4 ++-- > arch/arm64/tools/sysreg | 4 ++++ > 5 files changed, 33 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 498f922f4f41..0e57827a0cf2 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -547,7 +547,8 @@ struct kvm_vcpu_arch { > /* Statistical profiling extension */ > u64 pmscr_el1; > /* Self-hosted trace */ > - u64 trfcr_el1; > + u64 host_trfcr_el1; > + u64 guest_trfcr_el1; > } host_debug_state;
I think it is high time we stop having *guest* state in a structure that is obviously for the host, starting by moving the breakpoint and watchpoint out, and into the sysreg array.
And then TRFCR_EL1 can join the fun. But it is pretty unclear whether that's actually the guest state.
> > /* VGIC state */ > @@ -1097,6 +1098,8 @@ void kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu *vcpu); > void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr); > void kvm_clr_pmu_events(u32 clr); > bool kvm_set_pmuserenr(u64 val); > +void kvm_etm_set_guest_trfcr(u64 trfcr_guest); > +void kvm_etm_update_vcpu_events(struct kvm_vcpu *vcpu); > #else > static inline void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr) {} > static inline void kvm_clr_pmu_events(u32 clr) {} > @@ -1104,6 +1107,7 @@ static inline bool kvm_set_pmuserenr(u64 val) > { > return false; > } > +static inline void kvm_etm_set_guest_trfcr(u64 trfcr_guest) {} > #endif > > void kvm_vcpu_load_sysregs_vhe(struct kvm_vcpu *vcpu); > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index 1bfdd583b261..65e805dc1d7a 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -958,6 +958,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu) > kvm_vgic_flush_hwstate(vcpu); > > kvm_pmu_update_vcpu_events(vcpu); > + kvm_etm_update_vcpu_events(vcpu); > > /* > * Ensure we set mode to IN_GUEST_MODE after we disable > diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c > index 6a1bad1a921b..379d2677961f 100644 > --- a/arch/arm64/kvm/debug.c > +++ b/arch/arm64/kvm/debug.c > @@ -22,6 +22,7 @@ > DBG_MDSCR_MDE) > > static DEFINE_PER_CPU(u64, mdcr_el2); > +static DEFINE_PER_CPU(u64, guest_trfcr);
Hold on a sec. Why is that global? I'd expect the tracing to be specific to a vcpu, and not to affect *everything*.
> > /** > * save/restore_guest_debug_regs > @@ -342,3 +343,23 @@ void kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu *vcpu) > vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_SPE); > vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_TRFCR); > } > + > +void kvm_etm_set_guest_trfcr(u64 trfcr_guest) > +{ > + if (has_vhe()) > + write_sysreg_s(trfcr_guest, SYS_TRFCR_EL12); > + else > + *this_cpu_ptr(&guest_trfcr) = trfcr_guest; > +} > +EXPORT_SYMBOL_GPL(kvm_etm_set_guest_trfcr);
In what context can this be called? What if we want to expose TRFCR to guests instead? It looks to me that this ultimately precludes such use.
> + > +/* > + * Updates the vcpu's view of the etm events for this cpu. Must be > + * called before every vcpu run after disabling interrupts, to ensure > + * that an interrupt cannot fire and update the structure. > + */ > +void kvm_etm_update_vcpu_events(struct kvm_vcpu *vcpu) > +{ > + if (!has_vhe() && vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_TRFCR)) > + vcpu->arch.host_debug_state.guest_trfcr_el1 = *this_cpu_ptr(&guest_trfcr);
But what is the point of this per-vcpu field if all you care about is some per-CPU data?
> +} > diff --git a/arch/arm64/kvm/hyp/nvhe/debug-sr.c b/arch/arm64/kvm/hyp/nvhe/debug-sr.c > index 89c208112eb7..55bc01e9808f 100644 > --- a/arch/arm64/kvm/hyp/nvhe/debug-sr.c > +++ b/arch/arm64/kvm/hyp/nvhe/debug-sr.c > @@ -86,7 +86,7 @@ void __debug_save_host_buffers_nvhe(struct kvm_vcpu *vcpu) > __debug_save_spe(&vcpu->arch.host_debug_state.pmscr_el1); > /* Disable and flush Self-Hosted Trace generation */ > if (vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_TRFCR)) > - __debug_save_trace(&vcpu->arch.host_debug_state.trfcr_el1); > + __debug_save_trace(&vcpu->arch.host_debug_state.host_trfcr_el1); > } `<> > void __debug_switch_to_guest(struct kvm_vcpu *vcpu) > @@ -99,7 +99,7 @@ void __debug_restore_host_buffers_nvhe(struct kvm_vcpu *vcpu) > if (vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_SPE)) > __debug_restore_spe(vcpu->arch.host_debug_state.pmscr_el1); > if (vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_TRFCR)) > - __debug_restore_trace(vcpu->arch.host_debug_state.trfcr_el1); > + __debug_restore_trace(vcpu->arch.host_debug_state.host_trfcr_el1); > } > > void __debug_switch_to_host(struct kvm_vcpu *vcpu) > diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg > index 992722c0c23b..295a4a625b8b 100644 > --- a/arch/arm64/tools/sysreg > +++ b/arch/arm64/tools/sysreg > @@ -2661,3 +2661,7 @@ EndSysreg > Sysreg TRFCR_EL2 3 4 1 2 1 > Fields TRFCR_EL2 > EndSysreg > + > +Sysreg TRFCR_EL12 3 5 1 2 1 > +Fields TRFCR_ELx > +EndSysreg
Please move this to the first patch.
M.
-- Without deviation from the norm, progress is not possible.
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