Messages in this thread | | | Date | Wed, 22 Nov 2023 18:10:02 +0000 | Subject | Re: [PATCH v3 4/6] arm64: KVM: Add interface to set guest value for TRFCR register | From | Suzuki K Poulose <> |
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On 16/11/2023 19:26, Suzuki K Poulose wrote: > On 19/10/2023 17:55, James Clark 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, the host trace is controlled by TRFCR_EL2 and thus we can write to >> the TRFCR_EL1 immediately. Because guest writes to the register are >> trapped, the value will persist and can't be modified. > > This could also be added below to make it easier for the code reader. > >> >> 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. >> >> Signed-off-by: James Clark <james.clark@arm.com> >> --- >> arch/arm64/include/asm/kvm_host.h | 3 +++ >> arch/arm64/kvm/arm.c | 1 + >> arch/arm64/kvm/debug.c | 26 ++++++++++++++++++++++++++ >> 3 files changed, 30 insertions(+) >> >> diff --git a/arch/arm64/include/asm/kvm_host.h >> b/arch/arm64/include/asm/kvm_host.h >> index 0f0bf8e641bd..e1852102550d 100644 >> --- a/arch/arm64/include/asm/kvm_host.h >> +++ b/arch/arm64/include/asm/kvm_host.h >> @@ -1125,6 +1125,8 @@ 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) {} >> @@ -1132,6 +1134,7 @@ 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 0f717b6a9151..e4d846f2f665 100644 >> --- a/arch/arm64/kvm/arm.c >> +++ b/arch/arm64/kvm/arm.c >> @@ -1015,6 +1015,7 @@ 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 20cdd40b3c42..2ab41b954512 100644 >> --- a/arch/arm64/kvm/debug.c >> +++ b/arch/arm64/kvm/debug.c >> @@ -23,6 +23,12 @@ >> static DEFINE_PER_CPU(u64, mdcr_el2); >> +/* >> + * Per CPU value for TRFCR that should be applied to any guest vcpu >> that may >> + * run on that core in the future. >> + */ >> +static DEFINE_PER_CPU(u64, guest_trfcr); >> + >> /** >> * save/restore_guest_debug_regs >> * >> @@ -356,3 +362,23 @@ void kvm_arch_vcpu_put_debug_state_flags(struct >> kvm_vcpu *vcpu) >> vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_TRBE); >> vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_TRFCR); >> } >> + > > The comment in the description could be helpful here. > >> +void kvm_etm_set_guest_trfcr(u64 trfcr_guest) >> +{ >> + if (has_vhe())
I am wondering if "kvm" should do the extra safety check of making sure that the FEAT_TRF is available on the CPU, before actually writing to the register ? coresight calls this only when the FEAT_TRF is implemented. But given this is an exported function, may be we should be extra careful ?
Suzuki
>> + write_sysreg_s(trfcr_guest, SYS_TRFCR_EL12); >> + else >> + *this_cpu_ptr(&guest_trfcr) = trfcr_guest; >> +} >> +EXPORT_SYMBOL_GPL(kvm_etm_set_guest_trfcr); >> + >> +/* >> + * 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)) >> + ctxt_sys_reg(&vcpu->arch.ctxt, TRFCR_EL1) = >> *this_cpu_ptr(&guest_trfcr); >> +} > > Either way, > > Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
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