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

[James Clark <james.clark@arm.com>]

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