Commit f3020b88 authored Jul 30, 2020 by Thomas Gleixner

x86/kvm: Use __xfer_to_guest_mode_work_pending() in kvm_run_vcpu()



The comments explicitely explain that the work flags check and handling in
kvm_run_vcpu() is done with preemption and interrupts enabled as KVM
invokes the check again right before entering guest mode with interrupts
disabled which guarantees that the work flags are observed and handled
before VMENTER.

Nevertheless the flag pending check in kvm_run_vcpu() uses the helper
variant which requires interrupts to be disabled triggering an instant
lockdep splat. This was caught in testing before and then not fixed up in
the patch before applying. :(

Use the relaxed and intentionally racy __xfer_to_guest_mode_work_pending()
instead.

Fixes: 72c3c0fe ("x86/kvm: Use generic xfer to guest work function")
Reported-by: Qian Cai <cai@lca.pw> writes:
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/87bljxa2sa.fsf@nanos.tec.linutronix.de

parent 72c3c0fe

arch/x86/kvm/x86.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -8682,7 +8682,7 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
		break;
		}

		if (xfer_to_guest_mode_work_pending()) {
		if (__xfer_to_guest_mode_work_pending()) {
		srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
		r = xfer_to_guest_mode_handle_work(vcpu);
		if (r)

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