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Patch "KVM/x86: Remove indirect MSR op calls from SPEC_CTRL" has been added to the 4.9-stable tree

PATCH [email protected] 1 participant 1 message Mar 7, 2018

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This is a note to let you know that I've just added the patch titled

KVM/x86: Remove indirect MSR op calls from SPEC_CTRL

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-x86-remove-indirect-msr-op-calls-from-spec_ctrl.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From ecb586bd29c99fb4de599dec388658e74388daad Mon Sep 17 00:00:00 2001

From: Paolo Bonzini <[email protected]>
Date: Thu, 22 Feb 2018 16:43:17 +0100
Subject: KVM/x86: Remove indirect MSR op calls from SPEC_CTRL
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Paolo Bonzini <[email protected]>

commit ecb586bd29c99fb4de599dec388658e74388daad upstream.

Having a paravirt indirect call in the IBRS restore path is not a good idea, since we are trying to protect from speculative execution of bogus indirect branch targets. It is also slower, so use native_wrmsrl() on the vmentry path too.

Signed-off-by Paolo Bonzini <[email protected]>
Reviewed-by Jim Mattson <[email protected]>
Cc David Woodhouse <[email protected]>
Cc KarimAllah Ahmed <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Radim Krčmář <[email protected]>
Cc Thomas Gleixner <[email protected]>
Cc [email protected]
Cc [email protected]
Fixes d28b387fb74da95d69d2615732f50cceb38e9a4d
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Ingo Molnar <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 arch/x86/kvm/svm.c |    7 ++++---
 arch/x86/kvm/vmx.c |    7 ++++---
 2 files changed, 8 insertions(+), 6 deletions(-)
arch/x86/kvm/svm.c +4 -3
@@ -44,6 +44,7 @@
 #include <asm/debugreg.h>
 #include <asm/kvm_para.h>
 #include <asm/irq_remapping.h>
+#include <asm/microcode.h>
 #include <asm/nospec-branch.h>
 
 #include <asm/virtext.h>

@@ -4919,7 +4920,7 @@ static void svm_vcpu_run(struct kvm_vcpu
 	 * being speculatively taken.
 	 */
 	if (svm->spec_ctrl)
-		wrmsrl(MSR_IA32_SPEC_CTRL, svm->spec_ctrl);
+		native_wrmsrl(MSR_IA32_SPEC_CTRL, svm->spec_ctrl);
 
 	asm volatile (
 		"push %%" _ASM_BP "; \n\t"

@@ -5029,10 +5030,10 @@ static void svm_vcpu_run(struct kvm_vcpu
 	 * save it.
 	 */
 	if (!msr_write_intercepted(vcpu, MSR_IA32_SPEC_CTRL))
-		rdmsrl(MSR_IA32_SPEC_CTRL, svm->spec_ctrl);
+		svm->spec_ctrl = native_read_msr(MSR_IA32_SPEC_CTRL);
 
 	if (svm->spec_ctrl)
-		wrmsrl(MSR_IA32_SPEC_CTRL, 0);
+		native_wrmsrl(MSR_IA32_SPEC_CTRL, 0);
 
 	/* Eliminate branch target predictions from guest mode */
 	vmexit_fill_RSB();
arch/x86/kvm/vmx.c +4 -3
@@ -49,6 +49,7 @@
 #include <asm/kexec.h>
 #include <asm/apic.h>
 #include <asm/irq_remapping.h>
+#include <asm/microcode.h>
 #include <asm/nospec-branch.h>
 
 #include "trace.h"

@@ -8906,7 +8907,7 @@ static void __noclone vmx_vcpu_run(struc
 	 * being speculatively taken.
 	 */
 	if (vmx->spec_ctrl)
-		wrmsrl(MSR_IA32_SPEC_CTRL, vmx->spec_ctrl);
+		native_wrmsrl(MSR_IA32_SPEC_CTRL, vmx->spec_ctrl);
 
 	vmx->__launched = vmx->loaded_vmcs->launched;
 	asm(

@@ -9042,10 +9043,10 @@ static void __noclone vmx_vcpu_run(struc
 	 * save it.
 	 */
 	if (!msr_write_intercepted(vcpu, MSR_IA32_SPEC_CTRL))
-		rdmsrl(MSR_IA32_SPEC_CTRL, vmx->spec_ctrl);
+		vmx->spec_ctrl = native_read_msr(MSR_IA32_SPEC_CTRL);
 
 	if (vmx->spec_ctrl)
-		wrmsrl(MSR_IA32_SPEC_CTRL, 0);
+		native_wrmsrl(MSR_IA32_SPEC_CTRL, 0);
 
 	/* Eliminate branch target predictions from guest mode */
 	vmexit_fill_RSB();

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/kvm-x86-fix-smram-accessing-even-if-vm-is-shutdown.patch queue-4.9/kvm-x86-remove-indirect-msr-op-calls-from-spec_ctrl.patch queue-4.9/kvm-mmu-fix-overlap-between-public-and-private-memslots.patch queue-4.9/kvm-vmx-optimize-vmx_vcpu_run-and-svm_vcpu_run-by-marking-the-rdmsr-path-as-unlikely.patch