5.15-stable review patch. If anyone has any objections, please let me know.
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From: Nicolas Saenz Julienne nsaenz@amazon.com
commit d6800af51c76b6dae20e6023bbdc9b3da3ab5121 upstream.
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: 1f4b34f825e8 ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/hyperv.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
--- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -701,10 +701,12 @@ static int stimer_set_count(struct kvm_v
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);