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: [email protected]
Fixes: 1f4b34f825e8 ("kvm/x86: Hyper-V SynIC timers")
Signed-off-by: Nicolas Saenz Julienne <[email protected]>
---
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);
--
2.40.1
Nicolas Saenz Julienne <[email protected]> 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: [email protected]
> Fixes: 1f4b34f825e8 ("kvm/x86: Hyper-V SynIC timers")
> Signed-off-by: Nicolas Saenz Julienne <[email protected]>
> ---
>
> 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 <[email protected]>
--
Vitaly
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
--
https://github.com/kvm-x86/linux/tree/next