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From:   Suzuki K Poulose <suzuki.poulose@arm.com>
To:     linux-arm-kernel@lists.infradead.org
Cc:     linux-kernel@vger.kernel.org, mathieu.poirier@linaro.org,
        mike.leach@linaro.org, anshuman.khandual@arm.com,
        leo.yan@linaro.org, Suzuki K Poulose <suzuki.poulose@arm.com>,
        Will Deacon <will@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Marc Zyngier <maz@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>
Subject: [PATCH v4 08/19] arm64: kvm: Enable access to TRBE support for host
Date:   Thu, 25 Feb 2021 19:35:32 +0000
Message-Id: <20210225193543.2920532-9-suzuki.poulose@arm.com>
In-Reply-To: <20210225193543.2920532-1-suzuki.poulose@arm.com>
References: <20210225193543.2920532-1-suzuki.poulose@arm.com>
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For a nvhe host, the EL2 must allow the EL1&0 translation
regime for TraceBuffer (MDCR_EL2.E2TB == 0b11). This must
be saved/restored over a trip to the guest. Also, before
entering the guest, we must flush any trace data if the
TRBE was enabled. And we must prohibit the generation
of trace while we are in EL1 by clearing the TRFCR_EL1.

For vhe, the EL2 must prevent the EL1 access to the Trace
Buffer.

Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
cc: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
Changes
 - Rebased to linux-next.
 - Re-enable TRBE access on host restore.
 - For nvhe, flush the trace and prohibit the
   trace while we are at guest.
---
 arch/arm64/include/asm/el2_setup.h | 13 +++++++++
 arch/arm64/include/asm/kvm_arm.h   |  2 ++
 arch/arm64/include/asm/kvm_host.h  |  2 ++
 arch/arm64/kernel/hyp-stub.S       |  3 ++-
 arch/arm64/kvm/debug.c             |  6 ++---
 arch/arm64/kvm/hyp/nvhe/debug-sr.c | 42 ++++++++++++++++++++++++++++++
 arch/arm64/kvm/hyp/nvhe/switch.c   |  1 +
 7 files changed, 65 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
index d77d358f9395..bda918948471 100644
--- a/arch/arm64/include/asm/el2_setup.h
+++ b/arch/arm64/include/asm/el2_setup.h
@@ -65,6 +65,19 @@
 						// use EL1&0 translation.
 
 .Lskip_spe_\@:
+	/* Trace buffer */
+	ubfx	x0, x1, #ID_AA64DFR0_TRBE_SHIFT, #4
+	cbz	x0, .Lskip_trace_\@		// Skip if TraceBuffer is not present
+
+	mrs_s	x0, SYS_TRBIDR_EL1
+	and	x0, x0, TRBIDR_PROG
+	cbnz	x0, .Lskip_trace_\@		// If TRBE is available at EL2
+
+	mov	x0, #(MDCR_EL2_E2TB_MASK << MDCR_EL2_E2TB_SHIFT)
+	orr	x2, x2, x0			// allow the EL1&0 translation
+						// to own it.
+
+.Lskip_trace_\@:
 	msr	mdcr_el2, x2			// Configure debug traps
 .endm
 
diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 94d4025acc0b..692c9049befa 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -278,6 +278,8 @@
 #define CPTR_EL2_DEFAULT	CPTR_EL2_RES1
 
 /* Hyp Debug Configuration Register bits */
+#define MDCR_EL2_E2TB_MASK	(UL(0x3))
+#define MDCR_EL2_E2TB_SHIFT	(UL(24))
 #define MDCR_EL2_TTRF		(1 << 19)
 #define MDCR_EL2_TPMS		(1 << 14)
 #define MDCR_EL2_E2PB_MASK	(UL(0x3))
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 3d10e6527f7d..80d0a1a82a4c 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -315,6 +315,8 @@ struct kvm_vcpu_arch {
 		struct kvm_guest_debug_arch regs;
 		/* Statistical profiling extension */
 		u64 pmscr_el1;
+		/* Self-hosted trace */
+		u64 trfcr_el1;
 	} host_debug_state;
 
 	/* VGIC state */
diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
index 678cd2c618ee..ba84502b582a 100644
--- a/arch/arm64/kernel/hyp-stub.S
+++ b/arch/arm64/kernel/hyp-stub.S
@@ -115,9 +115,10 @@ SYM_CODE_START_LOCAL(mutate_to_vhe)
 	mrs_s	x0, SYS_VBAR_EL12
 	msr	vbar_el1, x0
 
-	// Use EL2 translations for SPE and disable access from EL1
+	// Use EL2 translations for SPE & TRBE and disable access from EL1
 	mrs	x0, mdcr_el2
 	bic	x0, x0, #(MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT)
+	bic	x0, x0, #(MDCR_EL2_E2TB_MASK << MDCR_EL2_E2TB_SHIFT)
 	msr	mdcr_el2, x0
 
 	// Transfer the MM state from EL1 to EL2
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index dbc890511631..7b16f42d39f4 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -89,7 +89,7 @@ void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
  *  - 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)
  *
  * Additionally, KVM only traps guest accesses to the debug registers if
  * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
@@ -107,8 +107,8 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
 	trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
 
 	/*
-	 * This also clears MDCR_EL2_E2PB_MASK to disable guest access
-	 * to the profiling buffer.
+	 * This also clears MDCR_EL2_E2PB_MASK and MDCR_EL2_E2TB_MASK
+	 * to disable guest access to the profiling and trace buffers
 	 */
 	vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
 	vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
diff --git a/arch/arm64/kvm/hyp/nvhe/debug-sr.c b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
index f401724f12ef..9499e18dd28f 100644
--- a/arch/arm64/kvm/hyp/nvhe/debug-sr.c
+++ b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
@@ -58,10 +58,51 @@ static void __debug_restore_spe(u64 pmscr_el1)
 	write_sysreg_s(pmscr_el1, SYS_PMSCR_EL1);
 }
 
+static void __debug_save_trace(u64 *trfcr_el1)
+{
+
+	*trfcr_el1 = 0;
+
+	/* Check if we have TRBE */
+	if (!cpuid_feature_extract_unsigned_field(read_sysreg(id_aa64dfr0_el1),
+						  ID_AA64DFR0_TRBE_SHIFT))
+		return;
+
+	/* Check we can access the TRBE */
+	if ((read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_PROG))
+		return;
+
+	/* Check if the TRBE is enabled */
+	if (!(read_sysreg_s(SYS_TRBLIMITR_EL1) & TRBLIMITR_ENABLE))
+		return;
+	/*
+	 * Prohibit trace generation while we are in guest.
+	 * Since access to TRFCR_EL1 is trapped, the guest can't
+	 * modify the filtering set by the host.
+	 */
+	*trfcr_el1 = read_sysreg_s(SYS_TRFCR_EL1);
+	write_sysreg_s(0, SYS_TRFCR_EL1);
+	isb();
+	/* Drain the trace buffer to memory */
+	tsb_csync();
+	dsb(nsh);
+}
+
+static void __debug_restore_trace(u64 trfcr_el1)
+{
+	if (!trfcr_el1)
+		return;
+
+	/* Restore trace filter controls */
+	write_sysreg_s(trfcr_el1, SYS_TRFCR_EL1);
+}
+
 void __debug_save_host_buffers_nvhe(struct kvm_vcpu *vcpu)
 {
 	/* Disable and flush SPE data generation */
 	__debug_save_spe(&vcpu->arch.host_debug_state.pmscr_el1);
+	/* Disable and flush Self-Hosted Trace generation */
+	__debug_save_trace(&vcpu->arch.host_debug_state.trfcr_el1);
 }
 
 void __debug_switch_to_guest(struct kvm_vcpu *vcpu)
@@ -72,6 +113,7 @@ void __debug_switch_to_guest(struct kvm_vcpu *vcpu)
 void __debug_restore_host_buffers_nvhe(struct kvm_vcpu *vcpu)
 {
 	__debug_restore_spe(vcpu->arch.host_debug_state.pmscr_el1);
+	__debug_restore_trace(vcpu->arch.host_debug_state.trfcr_el1);
 }
 
 void __debug_switch_to_host(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
index 10eed66136a0..d6ea5c8b5551 100644
--- a/arch/arm64/kvm/hyp/nvhe/switch.c
+++ b/arch/arm64/kvm/hyp/nvhe/switch.c
@@ -95,6 +95,7 @@ static void __deactivate_traps(struct kvm_vcpu *vcpu)
 
 	mdcr_el2 &= MDCR_EL2_HPMN_MASK;
 	mdcr_el2 |= MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT;
+	mdcr_el2 |= MDCR_EL2_E2TB_MASK << MDCR_EL2_E2TB_SHIFT;
 
 	write_sysreg(mdcr_el2, mdcr_el2);
 	if (is_protected_kvm_enabled())
-- 
2.24.1