* [PATCH] kvmgt: Hold struct kvm reference
@ 2017-03-20 2:38 Alex Williamson
2017-03-20 6:58 ` Jike Song
0 siblings, 1 reply; 3+ messages in thread
From: Alex Williamson @ 2017-03-20 2:38 UTC (permalink / raw)
To: intel-gvt-dev
Cc: Jike Song, kvm, linux-kernel, Zhenyu Wang, stable, Paolo Bonzini,
Zhi Wang
The kvmgt code keeps a pointer to the struct kvm associated with the
device, but doesn't actually hold a reference to it. If we do unclean
shutdown testing (ie. killing the user process), then we can see the
kvm association to the device unset, which causes kvmgt to trigger a
device release via a work queue. Naturally we cannot guarantee that
the cached struct kvm pointer is still valid at this point without
holding a reference. The observed failure in this case is a stuck
cpu trying to acquire the spinlock from the invalid reference, but
other failure modes are clearly possible. Hold a reference to avoid
this.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Cc: stable@vger.kernel.org #v4.10
Cc: Jike Song <jike.song@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
---
drivers/gpu/drm/i915/gvt/kvmgt.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 84d801638ede..142b8bd4ba6b 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -1324,6 +1324,7 @@ static int kvmgt_guest_init(struct mdev_device *mdev)
vgpu->handle = (unsigned long)info;
info->vgpu = vgpu;
info->kvm = kvm;
+ kvm_get_kvm(info->kvm);
kvmgt_protect_table_init(info);
gvt_cache_init(vgpu);
@@ -1343,6 +1344,7 @@ static bool kvmgt_guest_exit(struct kvmgt_guest_info *info)
}
kvm_page_track_unregister_notifier(info->kvm, &info->track_node);
+ kvm_put_kvm(info->kvm);
kvmgt_protect_table_destroy(info);
gvt_cache_destroy(info->vgpu);
vfree(info);
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] kvmgt: Hold struct kvm reference
2017-03-20 2:38 [PATCH] kvmgt: Hold struct kvm reference Alex Williamson
@ 2017-03-20 6:58 ` Jike Song
2017-03-20 7:05 ` Zhenyu Wang
0 siblings, 1 reply; 3+ messages in thread
From: Jike Song @ 2017-03-20 6:58 UTC (permalink / raw)
To: Alex Williamson
Cc: intel-gvt-dev, kvm, linux-kernel, Zhenyu Wang, stable,
Paolo Bonzini, Zhi Wang
On 03/20/2017 10:38 AM, Alex Williamson wrote:
> The kvmgt code keeps a pointer to the struct kvm associated with the
> device, but doesn't actually hold a reference to it. If we do unclean
> shutdown testing (ie. killing the user process), then we can see the
> kvm association to the device unset, which causes kvmgt to trigger a
> device release via a work queue. Naturally we cannot guarantee that
> the cached struct kvm pointer is still valid at this point without
> holding a reference. The observed failure in this case is a stuck
> cpu trying to acquire the spinlock from the invalid reference, but
> other failure modes are clearly possible. Hold a reference to avoid
> this.
>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> Cc: stable@vger.kernel.org #v4.10
> Cc: Jike Song <jike.song@intel.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
> Cc: Zhi Wang <zhi.a.wang@intel.com>
> ---
Reviewed-by: Jike Song <jike.song@intel.com>
Thanks for the fix!
--
Thanks,
Jike
> drivers/gpu/drm/i915/gvt/kvmgt.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index 84d801638ede..142b8bd4ba6b 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -1324,6 +1324,7 @@ static int kvmgt_guest_init(struct mdev_device *mdev)
> vgpu->handle = (unsigned long)info;
> info->vgpu = vgpu;
> info->kvm = kvm;
> + kvm_get_kvm(info->kvm);
>
> kvmgt_protect_table_init(info);
> gvt_cache_init(vgpu);
> @@ -1343,6 +1344,7 @@ static bool kvmgt_guest_exit(struct kvmgt_guest_info *info)
> }
>
> kvm_page_track_unregister_notifier(info->kvm, &info->track_node);
> + kvm_put_kvm(info->kvm);
> kvmgt_protect_table_destroy(info);
> gvt_cache_destroy(info->vgpu);
> vfree(info);
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] kvmgt: Hold struct kvm reference
2017-03-20 6:58 ` Jike Song
@ 2017-03-20 7:05 ` Zhenyu Wang
0 siblings, 0 replies; 3+ messages in thread
From: Zhenyu Wang @ 2017-03-20 7:05 UTC (permalink / raw)
To: Jike Song
Cc: Alex Williamson, intel-gvt-dev, kvm, linux-kernel, stable,
Paolo Bonzini, Zhi Wang
[-- Attachment #1: Type: text/plain, Size: 2198 bytes --]
On 2017.03.20 14:58:06 +0800, Jike Song wrote:
> On 03/20/2017 10:38 AM, Alex Williamson wrote:
> > The kvmgt code keeps a pointer to the struct kvm associated with the
> > device, but doesn't actually hold a reference to it. If we do unclean
> > shutdown testing (ie. killing the user process), then we can see the
> > kvm association to the device unset, which causes kvmgt to trigger a
> > device release via a work queue. Naturally we cannot guarantee that
> > the cached struct kvm pointer is still valid at this point without
> > holding a reference. The observed failure in this case is a stuck
> > cpu trying to acquire the spinlock from the invalid reference, but
> > other failure modes are clearly possible. Hold a reference to avoid
> > this.
> >
> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> > Cc: stable@vger.kernel.org #v4.10
> > Cc: Jike Song <jike.song@intel.com>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
> > Cc: Zhi Wang <zhi.a.wang@intel.com>
> > ---
>
> Reviewed-by: Jike Song <jike.song@intel.com>
>
> Thanks for the fix!
>
queued in fixes tree, thanks!
>
> > drivers/gpu/drm/i915/gvt/kvmgt.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
> > index 84d801638ede..142b8bd4ba6b 100644
> > --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> > +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> > @@ -1324,6 +1324,7 @@ static int kvmgt_guest_init(struct mdev_device *mdev)
> > vgpu->handle = (unsigned long)info;
> > info->vgpu = vgpu;
> > info->kvm = kvm;
> > + kvm_get_kvm(info->kvm);
> >
> > kvmgt_protect_table_init(info);
> > gvt_cache_init(vgpu);
> > @@ -1343,6 +1344,7 @@ static bool kvmgt_guest_exit(struct kvmgt_guest_info *info)
> > }
> >
> > kvm_page_track_unregister_notifier(info->kvm, &info->track_node);
> > + kvm_put_kvm(info->kvm);
> > kvmgt_protect_table_destroy(info);
> > gvt_cache_destroy(info->vgpu);
> > vfree(info);
> >
--
Open Source Technology Center, Intel ltd.
$gpg --keyserver wwwkeys.pgp.net --recv-keys 4D781827
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 163 bytes --]
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2017-03-20 7:07 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2017-03-20 2:38 [PATCH] kvmgt: Hold struct kvm reference Alex Williamson
2017-03-20 6:58 ` Jike Song
2017-03-20 7:05 ` Zhenyu Wang
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.