From 5066faedd2f7fd0b423e757341ae8ce384582b2d Mon Sep 17 00:00:00 2001 From: Nicolas Saenz Julienne Date: Tue, 17 Oct 2023 15:51:02 +0000 Subject: [PATCH] KVM: x86: hyper-v: Don't auto-enable stimer on write from user-space 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 Reviewed-by: Vitaly Kuznetsov Link: https://lore.kernel.org/r/20231017155101.40677-1-nsaenz@amazon.com Signed-off-by: Sean Christopherson Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/hyperv.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index f9603df799bf..8922f63f5566 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -555,10 +555,12 @@ 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);