[RFC PATCH v3 20/29] KVM: arm64: Use vcpu->arch.mdcr_el2 to track value of mdcr_el2

[Reiji Watanabe]

Track the baseline guest value for mdcr_el2 in struct kvm_vcpu_arch.
Use this value when setting mdcr_el2 for the guest.

Currently this value is unchanged, but the following patches will set
trapping bits based on features supported for the guest.

No functional change intended.

Signed-off-by: Reiji Watanabe <reijiw at google.com>
---
 arch/arm64/include/asm/kvm_arm.h | 16 ++++++++++++++++
 arch/arm64/kvm/arm.c             |  1 +
 arch/arm64/kvm/debug.c           | 13 ++++---------
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index c1e0e1202f30..e81f21995314 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -333,6 +333,22 @@
 				 BIT(18) |		\
 				 GENMASK(16, 15))
 
+/*
+ * The default value for the guest below also clears MDCR_EL2_E2PB_MASK
+ * and MDCR_EL2_E2TB_MASK to disable guest access to the profiling and
+ * trace buffers.
+ */
+#define MDCR_GUEST_FLAGS_DEFAULT				\
+	(MDCR_EL2_TPM  | MDCR_EL2_TPMS | MDCR_EL2_TTRF |	\
+	 MDCR_EL2_TPMCR | MDCR_EL2_TDRA | MDCR_EL2_TDOSA)
+
+/* Bits that are copied from vcpu->arch.mdcr_el2 to set mdcr_el2 for guest. */
+#define MDCR_GUEST_FLAGS_TRACKED_MASK				\
+	(MDCR_EL2_TPM  | MDCR_EL2_TPMS | MDCR_EL2_TTRF |	\
+	 MDCR_EL2_TPMCR | MDCR_EL2_TDRA | MDCR_EL2_TDOSA |	\
+	 (MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT))
+
+
 /* For compatibility with fault code shared with 32-bit */
 #define FSC_FAULT	ESR_ELx_FSC_FAULT
 #define FSC_ACCESS	ESR_ELx_FSC_ACCESS
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index aa4aff2588b8..64b104ebee73 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1128,6 +1128,7 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
 	}
 
 	vcpu_reset_hcr(vcpu);
+	vcpu->arch.mdcr_el2 = MDCR_GUEST_FLAGS_DEFAULT;
 	if (has_vhe())
 		vcpu->arch.cptr_el2 = CPTR_EL2_VHE_GUEST_DEFAULT;
 	else
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index db9361338b2a..83330968a411 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -84,16 +84,11 @@ void kvm_arm_init_debug(void)
 static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
 {
 	/*
-	 * This also clears MDCR_EL2_E2PB_MASK and MDCR_EL2_E2TB_MASK
-	 * to disable guest access to the profiling and trace buffers
+	 * Keep the vcpu->arch.mdcr_el2 bits that are specified by
+	 * MDCR_GUEST_FLAGS_TRACKED_MASK.
 	 */
-	vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
-	vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
-				MDCR_EL2_TPMS |
-				MDCR_EL2_TTRF |
-				MDCR_EL2_TPMCR |
-				MDCR_EL2_TDRA |
-				MDCR_EL2_TDOSA);
+	vcpu->arch.mdcr_el2 &= MDCR_GUEST_FLAGS_TRACKED_MASK;
+	vcpu->arch.mdcr_el2 |= __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
 
 	/* Is the VM being debugged by userspace? */
 	if (vcpu->guest_debug)
-- 
2.34.0.rc1.387.gb447b232ab-goog