linux-kernel - [PATCH 04/10] arm64: head.S: Enable EL1 (host) access to SPE when entered at EL2

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Message-Id: <1485540470-11469-5-git-send-email-will.deacon@arm.com>
Date:   Fri, 27 Jan 2017 18:07:43 +0000
From:   Will Deacon <will.deacon@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     marc.zyngier@....com, mark.rutland@....com, kim.phillips@....com,
        alex.bennee@...aro.org, christoffer.dall@...aro.org,
        tglx@...utronix.de, peterz@...radead.org,
        alexander.shishkin@...ux.intel.com, robh@...nel.org,
        suzuki.poulose@....com, pawel.moll@....com,
        mathieu.poirier@...aro.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org, Will Deacon <will.deacon@....com>
Subject: [PATCH 04/10] arm64: head.S: Enable EL1 (host) access to SPE when entered at EL2

The SPE architecture requires each exception level to enable access
to the SPE controls for the exception level below it, since additional
context-switch logic may be required to handle the buffer safely.

This patch allows EL1 (host) access to the SPE controls when entered at
EL2.

Cc: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Will Deacon <will.deacon@....com>
---
 arch/arm64/kernel/head.S | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 4b1abac3485a..7f625d2e8e45 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -592,15 +592,26 @@ CPU_LE(	movk	x0, #0x30d0, lsl #16	)	// Clear EE and E0E on LE systems
 #endif
 
 	/* EL2 debug */
-	mrs	x0, id_aa64dfr0_el1		// Check ID_AA64DFR0_EL1 PMUVer
-	sbfx	x0, x0, #8, #4
+	mrs	x1, id_aa64dfr0_el1		// Check ID_AA64DFR0_EL1 PMUVer
+	sbfx	x0, x1, #8, #4
 	cmp	x0, #1
 	b.lt	4f				// Skip if no PMU present
 	mrs	x0, pmcr_el0			// Disable debug access traps
 	ubfx	x0, x0, #11, #5			// to EL2 and allow access to
 4:
-	csel	x0, xzr, x0, lt			// all PMU counters from EL1
-	msr	mdcr_el2, x0			// (if they exist)
+	csel	x3, xzr, x0, lt			// all PMU counters from EL1
+
+	/* Statistical profiling */
+	ubfx	x0, x1, #32, #4			// Check ID_AA64DFR0_EL1 PMSVer
+	cbz	x0, 6f				// Skip if SPE not present
+	cbnz	x2, 5f				// VHE?
+	mov	x1, #(MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT)
+	orr	x3, x3, x1			// If we don't have VHE, then
+	b	6f				// use EL1&0 translation.
+5:						// For VHE, use EL2 translation
+	orr	x3, x3, #MDCR_EL2_TPMS		// and disable access from EL1
+6:
+	msr	mdcr_el2, x3			// Configure debug traps
 
 	/* Stage-2 translation */
 	msr	vttbr_el2, xzr
-- 
2.1.4