linux-kernel - [PATCH 3.13.y-ckt 51/86] KVM: Disable SMAP for guests in EPT realmode and EPT unpaging mode

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Message-Id: <1449096887-23017-52-git-send-email-kamal@canonical.com>
Date:	Wed,  2 Dec 2015 14:54:12 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Feng Wu <feng.wu@...el.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13.y-ckt 51/86] KVM: Disable SMAP for guests in EPT realmode and EPT unpaging mode

3.13.11-ckt31 -stable review patch.  If anyone has any objections, please let me know.

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

From: Feng Wu <feng.wu@...el.com>

commit e1e746b3c55d1d1e0841a2e600a154d8f6747232 upstream.

SMAP is disabled if CPU is in non-paging mode in hardware.
However KVM always uses paging mode to emulate guest non-paging
mode with TDP. To emulate this behavior, SMAP needs to be
manually disabled when guest switches to non-paging mode.

Signed-off-by: Feng Wu <feng.wu@...el.com>
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
[ kamal: 3.13-stable prereq for
  656ec4a KVM: VMX: fix SMEP and SMAP without EPT ]
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 arch/x86/kvm/vmx.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 9c2c662..45019f0 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3429,13 +3429,14 @@ static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 			hw_cr4 &= ~X86_CR4_PAE;
 			hw_cr4 |= X86_CR4_PSE;
 			/*
-			 * SMEP is disabled if CPU is in non-paging mode in
-			 * hardware. However KVM always uses paging mode to
+			 * SMEP/SMAP is disabled if CPU is in non-paging mode
+			 * in hardware. However KVM always uses paging mode to
 			 * emulate guest non-paging mode with TDP.
-			 * To emulate this behavior, SMEP needs to be manually
-			 * disabled when guest switches to non-paging mode.
+			 * To emulate this behavior, SMEP/SMAP needs to be
+			 * manually disabled when guest switches to non-paging
+			 * mode.
 			 */
-			hw_cr4 &= ~X86_CR4_SMEP;
+			hw_cr4 &= ~(X86_CR4_SMEP | X86_CR4_SMAP);
 		} else if (!(cr4 & X86_CR4_PAE)) {
 			hw_cr4 &= ~X86_CR4_PAE;
 		}
-- 
1.9.1

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