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Commit 8b3c3104 authored by Andy Honig's avatar Andy Honig Committed by Paolo Bonzini
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KVM: x86: Prevent host from panicking on shared MSR writes. 



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.

Cc: stable@vger.kernel.org
Signed-off-by: default avatarAndrew Honig <ahonig@google.com>
[Remove parts obsoleted by Nadav's patch. - Paolo]
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 854e8bb1

arch/x86/include/asm/kvm_host.h

+1 −1
Original line number Diff line number Diff line
@@ -1064,7 +1064,7 @@ void kvm_arch_mmu_notifier_invalidate_page(struct kvm *kvm, 
					   unsigned long address);



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);

arch/x86/kvm/vmx.c

+5 −2
Original line number Diff line number Diff line
@@ -2659,12 +2659,15 @@ 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,

				ret = kvm_set_shared_msr(msr->index, msr->data,

							 msr->mask);

				preempt_enable();

				if (ret)

					msr->data = old_msr_data;

			}

			break;

		}

arch/x86/kvm/x86.c

+8 −3
Original line number Diff line number Diff line
@@ -229,20 +229,25 @@ 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);