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Commit 6a1ac771 authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Avi Kivity
Browse files

KVM: MMU: fix missing locking in alloc_mmu_pages 



n_requested_mmu_pages/n_free_mmu_pages are used by
kvm_mmu_change_mmu_pages to calculate the number of pages to zap.

alloc_mmu_pages, called from the vcpu initialization path, modifies this
variables without proper locking, which can result in a negative value
in kvm_mmu_change_mmu_pages (say, with cpu hotplug).

Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 3662cb1c

arch/x86/kvm/mmu.c

+2 −0
Original line number Diff line number Diff line
@@ -2728,12 +2728,14 @@ static int alloc_mmu_pages(struct kvm_vcpu *vcpu) 


	ASSERT(vcpu);



	spin_lock(&vcpu->kvm->mmu_lock);

	if (vcpu->kvm->arch.n_requested_mmu_pages)

		vcpu->kvm->arch.n_free_mmu_pages =

					vcpu->kvm->arch.n_requested_mmu_pages;

	else

		vcpu->kvm->arch.n_free_mmu_pages =

					vcpu->kvm->arch.n_alloc_mmu_pages;

	spin_unlock(&vcpu->kvm->mmu_lock);

	/*

	 * When emulating 32-bit mode, cr3 is only 32 bits even on x86_64.

	 * Therefore we need to allocate shadow page tables in the first