linux-kernel - [PATCH 4.4 041/104] arm64: Dont trap host pointer auth use to EL2

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Date:   Thu, 24 Jan 2019 20:19:30 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Richard Henderson <richard.henderson@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Christoffer Dall <christoffer.dall@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        Will Deacon <will.deacon@....com>,
        kvmarm@...ts.cs.columbia.edu,
        Kristina Martsenko <kristina.martsenko@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 041/104] arm64: Dont trap host pointer auth use to EL2

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Backport of upstream commit b3669b1e1c09890d61109a1a8ece2c5b66804714 ]

To allow EL0 (and/or EL1) to use pointer authentication functionality,
we must ensure that pointer authentication instructions and accesses to
pointer authentication keys are not trapped to EL2.

This patch ensures that HCR_EL2 is configured appropriately when the
kernel is booted at EL2. For non-VHE kernels we set HCR_EL2.{API,APK},
ensuring that EL1 can access keys and permit EL0 use of instructions.
For VHE kernels host EL0 (TGE && E2H) is unaffected by these settings,
and it doesn't matter how we configure HCR_EL2.{API,APK}, so we don't
bother setting them.

This does not enable support for KVM guests, since KVM manages HCR_EL2
itself when running VMs.

Reviewed-by: Richard Henderson <richard.henderson@...aro.org>
Signed-off-by: Mark Rutland <mark.rutland@....com>
Acked-by: Christoffer Dall <christoffer.dall@....com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Marc Zyngier <marc.zyngier@....com>
Cc: Will Deacon <will.deacon@....com>
Cc: kvmarm@...ts.cs.columbia.edu
Signed-off-by: Will Deacon <will.deacon@....com>
[kristina: backport to 4.4.y: adjust context]
Signed-off-by: Kristina Martsenko <kristina.martsenko@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm64/include/asm/kvm_arm.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 013b7de45ee7..d7e7cf56e8d6 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -23,6 +23,8 @@
 #include <asm/types.h>
 
 /* Hyp Configuration Register (HCR) bits */
+#define HCR_API		(UL(1) << 41)
+#define HCR_APK		(UL(1) << 40)
 #define HCR_ID		(UL(1) << 33)
 #define HCR_CD		(UL(1) << 32)
 #define HCR_RW_SHIFT	31
@@ -81,7 +83,7 @@
 			 HCR_AMO | HCR_SWIO | HCR_TIDCP | HCR_RW)
 #define HCR_VIRT_EXCP_MASK (HCR_VA | HCR_VI | HCR_VF)
 #define HCR_INT_OVERRIDE   (HCR_FMO | HCR_IMO)
-#define HCR_HOST_NVHE_FLAGS (HCR_RW)
+#define HCR_HOST_NVHE_FLAGS (HCR_RW | HCR_API | HCR_APK)
 
 
 /* Hyp System Control Register (SCTLR_EL2) bits */
-- 
2.19.1