This is a note to let you know that I've just added the patch titled
KVM: x86: hyper-v: Don't auto-enable stimer on write from user-space
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-hyper-v-don-t-auto-enable-stimer-on-write-from-user-space.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d6800af51c76b6dae20e6023bbdc9b3da3ab5121 Mon Sep 17 00:00:00 2001
From: Nicolas Saenz Julienne <nsaenz@xxxxxxxxxx>
Date: Tue, 17 Oct 2023 15:51:02 +0000
Subject: KVM: x86: hyper-v: Don't auto-enable stimer on write from user-space
From: Nicolas Saenz Julienne <nsaenz@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Fixes: 1f4b34f825e8 ("kvm/x86: Hyper-V SynIC timers")
Signed-off-by: Nicolas Saenz Julienne <nsaenz@xxxxxxxxxx>
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20231017155101.40677-1-nsaenz@xxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -555,10 +555,12 @@ 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);
Patches currently in stable-queue which might be from nsaenz@xxxxxxxxxx are
queue-5.4/kvm-x86-hyper-v-don-t-auto-enable-stimer-on-write-from-user-space.patch
