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KVM: x86: hyper-v: Don't auto-enable stimer on write from user-space

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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: 1f4b34f825 ("kvm/x86: Hyper-V SynIC timers")
Signed-off-by: Nicolas Saenz Julienne <nsaenz@amazon.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20231017155101.40677-1-nsaenz@amazon.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Nicolas Saenz Julienne 2023-10-17 15:51:02 +00:00 committed by Sean Christopherson
parent 5a989bbead
commit d6800af51c
1 changed files with 6 additions and 4 deletions
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10
arch/x86/kvm/hyperv.c
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@ -727,10 +727,12 @@ static int stimer_set_count(struct kvm_vcpu_hv_stimer *stimer, u64 count,
stimer_cleanup(stimer);
stimer->count = count;
if (stimer->count == 0)
stimer->config.enable = 0;
else if (stimer->config.auto_enable)
stimer->config.enable = 1;
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);