Commit d6800af5 authored by Nicolas Saenz Julienne's avatar Nicolas Saenz Julienne Committed by Sean Christopherson
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KVM: x86: hyper-v: Don't auto-enable stimer on write from user-space 



Don't apply the stimer's counter side effects when modifying its
value from user-space, as this may trigger spurious interrupts.

For example:
 - The stimer is configured in auto-enable mode.
 - The stimer's count is set and the timer enabled.
 - The stimer expires, an interrupt is injected.
 - The VM is live migrated.
 - The stimer config and count are deserialized, auto-enable is ON, the
   stimer is re-enabled.
 - The stimer expires right away, and injects an unwarranted interrupt.

Cc: stable@vger.kernel.org
Fixes: 1f4b34f8 ("kvm/x86: Hyper-V SynIC timers")
Signed-off-by: default avatarNicolas Saenz Julienne <nsaenz@amazon.com>
Reviewed-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20231017155101.40677-1-nsaenz@amazon.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 5a989bbe

arch/x86/kvm/hyperv.c

+6 −4
Original line number Diff line number Diff line
@@ -727,10 +727,12 @@ static int stimer_set_count(struct kvm_vcpu_hv_stimer *stimer, u64 count, 


	stimer_cleanup(stimer);

	stimer->count = count;

	if (!host) {

		if (stimer->count == 0)

			stimer->config.enable = 0;

		else if (stimer->config.auto_enable)

			stimer->config.enable = 1;

	}



	if (stimer->config.enable)

		stimer_mark_pending(stimer, false);