linux-kernel - [RFC PATCH v4 24/39] KVM: arm64: debug: Configure MDCR

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Message-Id: <20210825161815.266051-25-alexandru.elisei@arm.com>
Date:   Wed, 25 Aug 2021 17:18:00 +0100
From:   Alexandru Elisei <alexandru.elisei@....com>
To:     maz@...nel.org, james.morse@....com, suzuki.poulose@....com,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        will@...nel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v4 24/39] KVM: arm64: debug: Configure MDCR_EL2 when a VCPU has SPE

Allow the guest running at EL1 to use SPE when that feature is enabled for
the VCPU by setting the profiling buffer owning translation regime to EL1&0
and disabling traps to the profiling control registers. Keep trapping
accesses to the buffer control registers because that's needed to emulate
the buffer management interrupt.

Signed-off-by: Alexandru Elisei <alexandru.elisei@....com>
---
 arch/arm64/include/asm/kvm_arm.h |  1 +
 arch/arm64/kvm/debug.c           | 23 +++++++++++++++++++----
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index d436831dd706..d939da6f54dc 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -285,6 +285,7 @@
 #define MDCR_EL2_TPMS		(1 << 14)
 #define MDCR_EL2_E2PB_MASK	(UL(0x3))
 #define MDCR_EL2_E2PB_SHIFT	(UL(12))
+#define MDCR_EL2_E2PB_EL1_TRAP	(UL(2))
 #define MDCR_EL2_TDRA		(1 << 11)
 #define MDCR_EL2_TDOSA		(1 << 10)
 #define MDCR_EL2_TDA		(1 << 9)
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index d5e79d7ee6e9..64e8211366b6 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -77,24 +77,39 @@ void kvm_arm_init_debug(void)
  *  - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR)
  *  - Debug ROM Address (MDCR_EL2_TDRA)
  *  - OS related registers (MDCR_EL2_TDOSA)
- *  - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB)
  *  - Self-hosted Trace Filter controls (MDCR_EL2_TTRF)
  *  - Self-hosted Trace (MDCR_EL2_TTRF/MDCR_EL2_E2TB)
  */
 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
+	 * This also clears MDCR_EL2_E2TB_MASK to disable guest access to the
+	 * trace buffers.
 	 */
 	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);
 
+	if (kvm_supports_spe() && kvm_vcpu_has_spe(vcpu)) {
+		/*
+		 * Use EL1&0 for the profiling buffer translation regime and
+		 * trap accesses to the buffer control registers; leave
+		 * MDCR_EL2.TPMS unset and do not trap accesses to the profiling
+		 * control registers.
+		 */
+		vcpu->arch.mdcr_el2 |= MDCR_EL2_E2PB_EL1_TRAP << MDCR_EL2_E2PB_SHIFT;
+	} else {
+		/*
+		 * Trap accesses to the profiling control registers; leave
+		 * MDCR_EL2.E2PB unset and use the EL2&0 translation regime for
+		 * the profiling buffer.
+		 */
+		vcpu->arch.mdcr_el2 |= MDCR_EL2_TPMS;
+	}
+
 	/* Is the VM being debugged by userspace? */
 	if (vcpu->guest_debug)
 		/* Route all software debug exceptions to EL2 */
-- 
2.33.0