* [PATCH] vhost: disable metadata prefetch optimization
@ 2019-07-26 11:51 Michael S. Tsirkin
2019-07-26 11:57 ` Jason Wang
0 siblings, 1 reply; 3+ messages in thread
From: Michael S. Tsirkin @ 2019-07-26 11:51 UTC (permalink / raw)
To: linux-kernel; +Cc: Jason Wang, kvm, virtualization, netdev
This seems to cause guest and host memory corruption.
Disable for now until we get a better handle on that.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
I put this in linux-next, we'll re-enable if we can fix
the outstanding issues in a short order.
drivers/vhost/vhost.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 819296332913..42a8c2a13ab1 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -96,7 +96,7 @@ struct vhost_uaddr {
};
#if defined(CONFIG_MMU_NOTIFIER) && ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE == 0
-#define VHOST_ARCH_CAN_ACCEL_UACCESS 1
+#define VHOST_ARCH_CAN_ACCEL_UACCESS 0
#else
#define VHOST_ARCH_CAN_ACCEL_UACCESS 0
#endif
--
MST
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] vhost: disable metadata prefetch optimization
2019-07-26 11:51 [PATCH] vhost: disable metadata prefetch optimization Michael S. Tsirkin
@ 2019-07-26 11:57 ` Jason Wang
2019-07-26 13:52 ` Michael S. Tsirkin
0 siblings, 1 reply; 3+ messages in thread
From: Jason Wang @ 2019-07-26 11:57 UTC (permalink / raw)
To: Michael S. Tsirkin, linux-kernel; +Cc: kvm, virtualization, netdev
On 2019/7/26 下午7:51, Michael S. Tsirkin wrote:
> This seems to cause guest and host memory corruption.
> Disable for now until we get a better handle on that.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>
> I put this in linux-next, we'll re-enable if we can fix
> the outstanding issues in a short order.
Btw, is this more suitable to e.g revert the
842aa64eddacd23adc6ecdbc69cb2030bec47122 and let syzbot fuzz more on the
current code?
I think we won't accept that patch eventually, so I suspect what syzbot
reports today is a false positives.
Thanks
>
> drivers/vhost/vhost.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index 819296332913..42a8c2a13ab1 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -96,7 +96,7 @@ struct vhost_uaddr {
> };
>
> #if defined(CONFIG_MMU_NOTIFIER) && ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE == 0
> -#define VHOST_ARCH_CAN_ACCEL_UACCESS 1
> +#define VHOST_ARCH_CAN_ACCEL_UACCESS 0
> #else
> #define VHOST_ARCH_CAN_ACCEL_UACCESS 0
> #endif
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] vhost: disable metadata prefetch optimization
2019-07-26 11:57 ` Jason Wang
@ 2019-07-26 13:52 ` Michael S. Tsirkin
0 siblings, 0 replies; 3+ messages in thread
From: Michael S. Tsirkin @ 2019-07-26 13:52 UTC (permalink / raw)
To: Jason Wang; +Cc: linux-kernel, kvm, virtualization, netdev
On Fri, Jul 26, 2019 at 07:57:25PM +0800, Jason Wang wrote:
>
> On 2019/7/26 下午7:51, Michael S. Tsirkin wrote:
> > This seems to cause guest and host memory corruption.
> > Disable for now until we get a better handle on that.
> >
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >
> > I put this in linux-next, we'll re-enable if we can fix
> > the outstanding issues in a short order.
>
>
> Btw, is this more suitable to e.g revert the
> 842aa64eddacd23adc6ecdbc69cb2030bec47122
Yes I did that too.
> and let syzbot fuzz more on the
> current code?
Current metadata direct access code is known to corrupt guest and host
memory - I don't feel we need more fuzzing.
>
> I think we won't accept that patch eventually, so I suspect what syzbot
> reports today is a false positives.
Today's reports are real, it's a bug in my patch. But I reverted it -
the below is an easier way to make sure at least linux-next is stable
for everyone.
>
> Thanks
>
>
> >
> > drivers/vhost/vhost.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> > index 819296332913..42a8c2a13ab1 100644
> > --- a/drivers/vhost/vhost.h
> > +++ b/drivers/vhost/vhost.h
> > @@ -96,7 +96,7 @@ struct vhost_uaddr {
> > };
> > #if defined(CONFIG_MMU_NOTIFIER) && ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE == 0
> > -#define VHOST_ARCH_CAN_ACCEL_UACCESS 1
> > +#define VHOST_ARCH_CAN_ACCEL_UACCESS 0
> > #else
> > #define VHOST_ARCH_CAN_ACCEL_UACCESS 0
> > #endif
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-07-26 11:57 ` Jason Wang
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