Commit 9c1a0744 authored by Wanpeng Li's avatar Wanpeng Li Committed by Paolo Bonzini
Browse files

KVM: x86/xen: Take srcu lock when accessing kvm_memslots() 



kvm_memslots() will be called by kvm_write_guest_offset_cached() so we should
take the srcu lock. Let's pull the srcu lock operation from kvm_steal_time_set_preempted()
again to fix xen part.

Fixes: 30b5c851 ("KVM: x86/xen: Add support for vCPU runstate information")
Signed-off-by: default avatarWanpeng Li <wanpengli@tencent.com>
Message-Id: <1619166200-9215-1-git-send-email-wanpengli@tencent.com>
Reviewed-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent bf05bf16

arch/x86/kvm/x86.c

+9 −11
Original line number Diff line number Diff line
@@ -4025,7 +4025,6 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu) 
{

	struct kvm_host_map map;

	struct kvm_steal_time *st;

	int idx;



	if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))

		return;
@@ -4033,15 +4032,9 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu) 
	if (vcpu->arch.st.preempted)

		return;



	/*

	 * Take the srcu lock as memslots will be accessed to check the gfn

	 * cache generation against the memslots generation.

	 */

	idx = srcu_read_lock(&vcpu->kvm->srcu);



	if (kvm_map_gfn(vcpu, vcpu->arch.st.msr_val >> PAGE_SHIFT, &map,

			&vcpu->arch.st.cache, true))

		goto out;

		return;



	st = map.hva +

		offset_in_page(vcpu->arch.st.msr_val & KVM_STEAL_VALID_BITS);
@@ -4049,20 +4042,25 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu) 
	st->preempted = vcpu->arch.st.preempted = KVM_VCPU_PREEMPTED;



	kvm_unmap_gfn(vcpu, &map, &vcpu->arch.st.cache, true, true);



out:

	srcu_read_unlock(&vcpu->kvm->srcu, idx);

}



void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)

{

	int idx;



	if (vcpu->preempted && !vcpu->arch.guest_state_protected)

		vcpu->arch.preempted_in_kernel = !static_call(kvm_x86_get_cpl)(vcpu);



	/*

	 * Take the srcu lock as memslots will be accessed to check the gfn

	 * cache generation against the memslots generation.

	 */

	idx = srcu_read_lock(&vcpu->kvm->srcu);

	if (kvm_xen_msr_enabled(vcpu->kvm))

		kvm_xen_runstate_set_preempted(vcpu);

	else

		kvm_steal_time_set_preempted(vcpu);

	srcu_read_unlock(&vcpu->kvm->srcu, idx);



	static_call(kvm_x86_vcpu_put)(vcpu);

	vcpu->arch.last_host_tsc = rdtsc();