linux-kernel - [PATCH] arm64: KVM: Skip PSTATE.PAN reest at EL2 in non-VHE

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Date:   Mon, 11 Sep 2017 19:16:52 +0800
From:   Dongjiu Geng <gengdongjiu@...wei.com>
To:     <christoffer.dall@...aro.org>, <marc.zyngier@....com>,
        <vladimir.murzin@....com>, <james.morse@....com>
CC:     <gengdongjiu@...wei.com>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] arm64: KVM: Skip PSTATE.PAN reest at EL2 in non-VHE

PSTATE.PAN disables reading and/or writing to a userspace virtual
address from EL1 in non-VHE or from EL2 in VHE. In non-VHE, there is
no any userspace mapping at EL2, so no need to reest the PSTATE.PAN.

Signed-off-by: Dongjiu Geng <gengdongjiu@...wei.com>
Signed-off-by: Haibin Zhang <zhanghaibin7@...wei.com>
---
 arch/arm64/kvm/hyp/entry.S | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index 12ee62d6d410..86a7549b1b4c 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -96,8 +96,12 @@ ENTRY(__guest_exit)
 
 	add	x1, x1, #VCPU_CONTEXT
 
-	ALTERNATIVE(nop, SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
+alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
+	b	2f			// skip PAN at EL2 in non-VHE
+alternative_else_nop_endif
 
+	ALTERNATIVE(nop, SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
+2:
 	// Store the guest regs x2 and x3
 	stp	x2, x3,   [x1, #CPU_XREG_OFFSET(2)]
 
-- 
2.14.1