linux-kernel - [PATCH 4.19 234/280] arm64: KVM: Fix architecturally invalid reset value for FPEXC32

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Date:   Fri, 22 Mar 2019 12:16:27 +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,
        Christoffer Dall <christoffer.dall@....com>,
        Dave Martin <Dave.Martin@....com>,
        Marc Zyngier <marc.zyngier@....com>
Subject: [PATCH 4.19 234/280] arm64: KVM: Fix architecturally invalid reset value for FPEXC32_EL2

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

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

From: Dave Martin <Dave.Martin@....com>

commit c88b093693ccbe41991ef2e9b1d251945e6e54ed upstream.

Due to what looks like a typo dating back to the original addition
of FPEXC32_EL2 handling, KVM currently initialises this register to
an architecturally invalid value.

As a result, the VECITR field (RES1) in bits [10:8] is initialised
with 0, and the two reserved (RES0) bits [6:5] are initialised with
1.  (In the Common VFP Subarchitecture as specified by ARMv7-A,
these two bits were IMP DEF.  ARMv8-A removes them.)

This patch changes the reset value from 0x70 to 0x700, which
reflects the architectural constraints and is presumably what was
originally intended.

Cc: <stable@...r.kernel.org> # 4.12.x-
Cc: Christoffer Dall <christoffer.dall@....com>
Fixes: 62a89c44954f ("arm64: KVM: 32bit handling of coprocessor traps")
Signed-off-by: Dave Martin <Dave.Martin@....com>
Signed-off-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm64/kvm/sys_regs.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1456,7 +1456,7 @@ static const struct sys_reg_desc sys_reg

 	{ SYS_DESC(SYS_DACR32_EL2), NULL, reset_unknown, DACR32_EL2 },
 	{ SYS_DESC(SYS_IFSR32_EL2), NULL, reset_unknown, IFSR32_EL2 },
-	{ SYS_DESC(SYS_FPEXC32_EL2), NULL, reset_val, FPEXC32_EL2, 0x70 },
+	{ SYS_DESC(SYS_FPEXC32_EL2), NULL, reset_val, FPEXC32_EL2, 0x700 },
 };

 static bool trap_dbgidr(struct kvm_vcpu *vcpu,