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 ---
Changes since v2: - reword commit message/subject.
Changes since v1: - Cover all 'stimer->config.enable' updates.
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 7c2dac6824e2..238afd7335e4 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -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);
Nicolas Saenz Julienne nsaenz@amazon.com writes:
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
Changes since v2:
- reword commit message/subject.
Changes since v1:
- Cover all 'stimer->config.enable' updates.
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 7c2dac6824e2..238afd7335e4 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -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);
LGTM, thanks!
Reviewed-by: Vitaly Kuznetsov vkuznets@redhat.com
On Tue, 17 Oct 2023 15:51:02 +0000, Nicolas Saenz Julienne wrote:
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.
[...]
Applied to kvm-x86 misc, thanks!
[1/1] KVM: x86: hyper-v: Don't auto-enable stimer on write from user-space https://github.com/kvm-x86/linux/commit/d6800af51c76
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