linux-kernel - [PATCH V3 10/14] arm64: nvhe: Allow TRBE access at EL1

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Date:   Wed, 27 Jan 2021 14:25:34 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-arm-kernel@...ts.infradead.org, coresight@...ts.linaro.org
Cc:     mathieu.poirier@...aro.org, suzuki.poulose@....com,
        mike.leach@...aro.org, lcherian@...vell.com,
        linux-kernel@...r.kernel.org,
        Anshuman Khandual <anshuman.khandual@....com>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH V3 10/14] arm64: nvhe: Allow TRBE access at EL1

From: Suzuki K Poulose <suzuki.poulose@....com>

When the kernel is booted at EL2 in a nvhe configuration,
enable the TRBE access to the EL1. The EL1 still can't trace
EL2, unless EL2 permits explicitly via TRFCR_EL2.E2TRE.

Cc: Will Deacon <will@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Marc Zyngier <maz@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
cc: Anshuman Khandual <anshuman.khandual@....com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
 arch/arm64/include/asm/el2_setup.h | 19 +++++++++++++++++++
 arch/arm64/include/asm/kvm_arm.h   |  2 ++
 2 files changed, 21 insertions(+)

diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
index a7f5a1b..05ecce9 100644
--- a/arch/arm64/include/asm/el2_setup.h
+++ b/arch/arm64/include/asm/el2_setup.h
@@ -72,6 +72,25 @@
 .endif
 
 3:
+
+.ifeqs	"\mode", "nvhe"
+	/*
+	 * If the Trace Buffer is available, allow
+	 * the EL1 to own it. Note that EL1 cannot
+	 * trace the EL2, as it is prevented by
+	 * TRFCR_EL2.E2TRE == 0.
+	 */
+	ubfx	x0, x1, #ID_AA64DFR0_TRBE_SHIFT, #4
+	cbz	x0, 1f
+
+	mrs_s	x0, SYS_TRBIDR_EL1
+	and	x0, x0, TRBIDR_PROG
+	cbnz	x0, 1f
+	mov	x0, #(MDCR_EL2_E2TB_EL1_OWN << MDCR_EL2_E2TB_SHIFT)
+	orr	x2, x2, x0
+.endif
+
+1:
 	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 4e90c2d..ed8b789 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -281,6 +281,8 @@
 #define MDCR_EL2_TPMS		(1 << 14)
 #define MDCR_EL2_E2PB_MASK	(UL(0x3))
 #define MDCR_EL2_E2PB_SHIFT	(UL(12))
+#define MDCR_EL2_E2TB_EL1_OWN	(UL(0x3))
+#define MDCR_EL2_E2TB_SHIFT	(UL(24))
 #define MDCR_EL2_TDRA		(1 << 11)
 #define MDCR_EL2_TDOSA		(1 << 10)
 #define MDCR_EL2_TDA		(1 << 9)
-- 
2.7.4