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

James Clark
2023-10-19T16:56:25Z

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>
---
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);
}
--
2.34.1