Re: [PATCH v3 3/6] arm64: KVM: Add iflag for FEAT_TRF

Suzuki K Poulose
2023-11-16T19:27:17Z

On 19/10/2023 17:55, James Clark wrote:
> Add an extra iflag to signify if the TRFCR register is accessible.
> Because TRBE requires FEAT_TRF, DEBUG_STATE_SAVE_TRBE still has the same
> behavior even though it's only set when FEAT_TRF is present.
>
> The following holes are left in struct kvm_vcpu_arch, but there aren't
> enough other 8 bit fields to rearrange it to leave any hole smaller than
> 7 bytes:
>
> u8 cflags; /* 2292 1 */
> /* XXX 1 byte hole, try to pack */
> u16 iflags; /* 2294 2 */
> u8 sflags; /* 2296 1 */
> bool pause; /* 2297 1 */
> /* XXX 6 bytes hole, try to pack */
>
> Signed-off-by: James Clark <james.clark@arm.com>

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>

> ---
> arch/arm64/include/asm/kvm_host.h | 4 +++-
> arch/arm64/kvm/debug.c | 22 ++++++++++++++++++----
> 2 files changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 7c82927ddaf2..0f0bf8e641bd 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -535,7 +535,7 @@ struct kvm_vcpu_arch {
> u8 cflags;
>
> /* Input flags to the hypervisor code, potentially cleared after use */
> - u8 iflags;
> + u16 iflags;
>
> /* State flags for kernel bookkeeping, unused by the hypervisor code */
> u8 sflags;
> @@ -741,6 +741,8 @@ struct kvm_vcpu_arch {
> #define DEBUG_STATE_SAVE_TRBE __vcpu_single_flag(iflags, BIT(6))
> /* vcpu running in HYP context */
> #define VCPU_HYP_CONTEXT __vcpu_single_flag(iflags, BIT(7))
> +/* Save trace filter controls */
> +#define DEBUG_STATE_SAVE_TRFCR __vcpu_single_flag(iflags, BIT(8))
>
> /* SVE enabled for host EL0 */
> #define HOST_SVE_ENABLED __vcpu_single_flag(sflags, BIT(0))
> diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
> index 8725291cb00a..20cdd40b3c42 100644
> --- a/arch/arm64/kvm/debug.c
> +++ b/arch/arm64/kvm/debug.c
> @@ -331,14 +331,28 @@ void kvm_arch_vcpu_load_debug_state_flags(struct kvm_vcpu *vcpu)
> !(read_sysreg_s(SYS_PMBIDR_EL1) & BIT(PMBIDR_EL1_P_SHIFT)))
> vcpu_set_flag(vcpu, DEBUG_STATE_SAVE_SPE);
>
> - /* Check if we have TRBE implemented and available at the host */
> - if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_TraceBuffer_SHIFT) &&
> - !(read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_EL1_P))
> - vcpu_set_flag(vcpu, DEBUG_STATE_SAVE_TRBE);
> + /*
> + * Save TRFCR on nVHE if FEAT_TRF (TraceFilt) exists. This will be
> + * done in cases where use of TRBE doesn't completely disable trace and
> + * handles the exclude_host/exclude_guest rules of the trace session.
> + */
> + if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_TraceFilt_SHIFT)) {
> + vcpu_set_flag(vcpu, DEBUG_STATE_SAVE_TRFCR);
> + /*
> + * Check if we have TRBE implemented and available at the host. If it's
> + * in use at the time of guest switch it will need to be disabled and
> + * then restored. The architecture mandates FEAT_TRF with TRBE, so we
> + * only need to check for TRBE after TRF.
> + */
> + if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_TraceBuffer_SHIFT) &&
> + !(read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_EL1_P))
> + vcpu_set_flag(vcpu, DEBUG_STATE_SAVE_TRBE);
> + }
> }
>
> 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_TRBE);
> + vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_TRFCR);
> }