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From: Julian Stecklina <jsteckli@amazon.de>
To: kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>
Cc: Julian Stecklina <jsteckli@amazon.de>,
	js@alien8.de, linux-kernel@vger.kernel.org
Subject: [PATCH 2/4] kvm, vmx: move register clearing out of assembly path
Date: Wed, 24 Oct 2018 10:28:57 +0200	[thread overview]
Message-ID: <558fea0b4df498eefcaea5ae07a089ad9706c1a2.1540369608.git.jsteckli@amazon.de> (raw)
In-Reply-To: <09986c98c9655f1542768ecfda644ac821e67a57.1540369608.git.jsteckli@amazon.de>
In-Reply-To: <09986c98c9655f1542768ecfda644ac821e67a57.1540369608.git.jsteckli@amazon.de>

Split the security related register clearing out of the large inline
assembly VM entry path. This results in two slightly less complicated
inline assembly statements, where it is clearer what each one does.

Signed-off-by: Julian Stecklina <jsteckli@amazon.de>
Reviewed-by: Jan H. Schönherr <jschoenh@amazon.de>
Reviewed-by: Konrad Jan Miller <kjm@amazon.de>
---
 arch/x86/kvm/vmx.c | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 93562d5..9225099 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -10797,20 +10797,7 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
 		"mov %%r13, %c[r13](%0) \n\t"
 		"mov %%r14, %c[r14](%0) \n\t"
 		"mov %%r15, %c[r15](%0) \n\t"
-		"xor %%r8d,  %%r8d \n\t"
-		"xor %%r9d,  %%r9d \n\t"
-		"xor %%r10d, %%r10d \n\t"
-		"xor %%r11d, %%r11d \n\t"
-		"xor %%r12d, %%r12d \n\t"
-		"xor %%r13d, %%r13d \n\t"
-		"xor %%r14d, %%r14d \n\t"
-		"xor %%r15d, %%r15d \n\t"
 #endif
-
-		"xor %%eax, %%eax \n\t"
-		"xor %%ebx, %%ebx \n\t"
-		"xor %%esi, %%esi \n\t"
-		"xor %%edi, %%edi \n\t"
 		"pop  %%" _ASM_BP "; pop  %%" _ASM_DX " \n\t"
 		".pushsection .rodata \n\t"
 		".global vmx_return \n\t"
@@ -10847,6 +10834,26 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
 #endif
 	      );
 
+	/* Don't let guest register values survive. */
+	asm volatile (
+		""
+#ifdef CONFIG_X86_64
+		"xor %%r8d,  %%r8d \n\t"
+		"xor %%r9d,  %%r9d \n\t"
+		"xor %%r10d, %%r10d \n\t"
+		"xor %%r11d, %%r11d \n\t"
+		"xor %%r12d, %%r12d \n\t"
+		"xor %%r13d, %%r13d \n\t"
+		"xor %%r14d, %%r14d \n\t"
+		"xor %%r15d, %%r15d \n\t"
+#endif
+		:: "a" (0), "b" (0), "S" (0), "D" (0)
+		: "cc"
+#ifdef CONFIG_X86_64
+		  , "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15"
+#endif
+		);
+
 	/*
 	 * We do not use IBRS in the kernel. If this vCPU has used the
 	 * SPEC_CTRL MSR it may have left it on; save the value and
-- 
2.7.4


  reply	other threads:[~2018-10-24  8:29 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-24  8:28 [PATCH 1/4] kvm, vmx: move CR2 context switch " Julian Stecklina
2018-10-24  8:28 ` Julian Stecklina [this message]
2018-10-25 16:55   ` [PATCH 2/4] kvm, vmx: move register clearing " Jim Mattson
2018-10-26 10:31     ` Stecklina, Julian
2018-10-26 15:46   ` Sean Christopherson
2018-10-26 16:30     ` Jim Mattson
2018-10-29 13:47       ` Stecklina, Julian
2018-10-24  8:28 ` [PATCH 3/4] kvm, vmx: fix __invvpid style Julian Stecklina
2018-10-24  8:28 ` [PATCH 4/4] kvm, vmx: remove manually coded vmx instructions Julian Stecklina
2018-10-24 17:44   ` Eric Northup
2018-10-26 10:46     ` Stecklina, Julian
2018-10-26 14:30       ` Sean Christopherson
2018-10-25 17:02 ` [PATCH 1/4] kvm, vmx: move CR2 context switch out of assembly path Jim Mattson

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