This is a note to let you know that I've just added the patch titled
KVM: x86: Prevent host from panicking on shared MSR writes.
to the 3.17-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-prevent-host-from-panicking-on-shared-msr-writes.patch
and it can be found in the queue-3.17 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 8b3c3104c3f4f706e99365c3e0d2aa61b95f969f Mon Sep 17 00:00:00 2001
From: Andy Honig <ahonig@xxxxxxxxxx>
Date: Wed, 27 Aug 2014 11:16:44 -0700
Subject: KVM: x86: Prevent host from panicking on shared MSR writes.
From: Andy Honig <ahonig@xxxxxxxxxx>
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@xxxxxxxxxx>
[Remove parts obsoleted by Nadav's patch. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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(-)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1049,7 +1049,7 @@ int kvm_cpu_get_interrupt(struct kvm_vcp
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);
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2632,12 +2632,15 @@ static int vmx_set_msr(struct kvm_vcpu *
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;
}
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -229,20 +229,25 @@ static void kvm_shared_msr_cpu_online(vo
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);
Patches currently in stable-queue which might be from ahonig@xxxxxxxxxx are
queue-3.17/kvm-x86-prevent-host-from-panicking-on-shared-msr-writes.patch
queue-3.17/kvm-x86-improve-thread-safety-in-pit.patch
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