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[3.16.y-ckt,extended,stable] Patch "KVM: x86: Prevent host from panicking on shared MSR writes." has been added to staging queue

Message ID 1415619108-9387-1-git-send-email-luis.henriques@canonical.com
State New
Headers show

Commit Message

Luis Henriques Nov. 10, 2014, 11:31 a.m. UTC 
This is a note to let you know that I have just added a patch titled

    KVM: x86: Prevent host from panicking on shared MSR writes.

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt1.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

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From 78c4e454576b138b7a7b1d064e14b646b4e45ba4 Mon Sep 17 00:00:00 2001
From: Andy Honig <ahonig@google.com>
Date: Wed, 27 Aug 2014 11:16:44 -0700
Subject: KVM: x86: Prevent host from panicking on shared MSR writes.

commit 8b3c3104c3f4f706e99365c3e0d2aa61b95f969f upstream.

The previous patch blocked invalid writes directly when the MSR
is written.  As a precaution, prevent future similar mistakes by
gracefulling handle GPs caused by writes to shared MSRs.

Signed-off-by: Andrew Honig <ahonig@google.com>
[Remove parts obsoleted by Nadav's patch. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 arch/x86/include/asm/kvm_host.h |  2 +-
 arch/x86/kvm/vmx.c              |  7 +++++--
 arch/x86/kvm/x86.c              | 11 ++++++++---
 3 files changed, 14 insertions(+), 6 deletions(-)

--
2.1.0
diff mbox

Patch

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c7172a1e6b53..3d9bcc6b9d99 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1061,7 +1061,7 @@  int kvm_cpu_get_interrupt(struct kvm_vcpu *v);
 void kvm_vcpu_reset(struct kvm_vcpu *vcpu);

 void kvm_define_shared_msr(unsigned index, u32 msr);
-void kvm_set_shared_msr(unsigned index, u64 val, u64 mask);
+int kvm_set_shared_msr(unsigned index, u64 val, u64 mask);

 bool kvm_is_linear_rip(struct kvm_vcpu *vcpu, unsigned long linear_rip);

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 2a3bf6be0506..8aa791602cb1 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2615,12 +2615,15 @@  static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	default:
 		msr = find_msr_entry(vmx, msr_index);
 		if (msr) {
+			u64 old_msr_data = msr->data;
 			msr->data = data;
 			if (msr - vmx->guest_msrs < vmx->save_nmsrs) {
 				preempt_disable();
-				kvm_set_shared_msr(msr->index, msr->data,
-						   msr->mask);
+				ret = kvm_set_shared_msr(msr->index, msr->data,
+							 msr->mask);
 				preempt_enable();
+				if (ret)
+					msr->data = old_msr_data;
 			}
 			break;
 		}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c038486c9866..28e070af5030 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -227,20 +227,25 @@  static void kvm_shared_msr_cpu_online(void)
 		shared_msr_update(i, shared_msrs_global.msrs[i]);
 }

-void kvm_set_shared_msr(unsigned slot, u64 value, u64 mask)
+int kvm_set_shared_msr(unsigned slot, u64 value, u64 mask)
 {
 	unsigned int cpu = smp_processor_id();
 	struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu);
+	int err;

 	if (((value ^ smsr->values[slot].curr) & mask) == 0)
-		return;
+		return 0;
 	smsr->values[slot].curr = value;
-	wrmsrl(shared_msrs_global.msrs[slot], value);
+	err = wrmsrl_safe(shared_msrs_global.msrs[slot], value);
+	if (err)
+		return 1;
+
 	if (!smsr->registered) {
 		smsr->urn.on_user_return = kvm_on_user_return;
 		user_return_notifier_register(&smsr->urn);
 		smsr->registered = true;
 	}
+	return 0;
 }
 EXPORT_SYMBOL_GPL(kvm_set_shared_msr);