Linux Virtualization - Aug 2019 - [PATCH V5 0/9] Fixes for vhost metadata acceleration

On 2019/8/11 ??1:52, Michael S. Tsirkin wrote:
> On Fri, Aug 09, 2019 at 01:48:42AM -0400, Jason Wang wrote:
>> Hi all:
>>
>> This series try to fix several issues introduced by meta data
>> accelreation series. Please review.
>>
>> Changes from V4:
>> - switch to use spinlock synchronize MMU notifier with accessors
>>
>> Changes from V3:
>> - remove the unnecessary patch
>>
>> Changes from V2:
>> - use seqlck helper to synchronize MMU notifier with vhost worker
>>
>> Changes from V1:
>> - try not use RCU to syncrhonize MMU notifier with vhost worker
>> - set dirty pages after no readers
>> - return -EAGAIN only when we find the range is overlapped with
>>    metadata
>>
>> Jason Wang (9):
>>    vhost: don't set uaddr for invalid address
>>    vhost: validate MMU notifier registration
>>    vhost: fix vhost map leak
>>    vhost: reset invalidate_count in vhost_set_vring_num_addr()
>>    vhost: mark dirty pages during map uninit
>>    vhost: don't do synchronize_rcu() in vhost_uninit_vq_maps()
>>    vhost: do not use RCU to synchronize MMU notifier with worker
>>    vhost: correctly set dirty pages in MMU notifiers callback
>>    vhost: do not return -EAGAIN for non blocking invalidation too early
>>
>>   drivers/vhost/vhost.c | 202
+++++++++++++++++++++++++-----------------
>>   drivers/vhost/vhost.h |   6 +-
>>   2 files changed, 122 insertions(+), 86 deletions(-)
> This generally looks more solid.
>
> But this amounts to a significant overhaul of the code.
>
> At this point how about we revert 7f466032dc9e5a61217f22ea34b2df932786bbfc
> for this release, and then re-apply a corrected version
> for the next one?

If possible, consider we've actually disabled the feature. How about 
just queued those patches for next release?

Thanks

>
>> -- 
>> 2.18.1

From: Jason Wang <jasowang at redhat.com>
Date: Mon, 12 Aug 2019 10:44:51 +0800
> On 2019/8/11 ??1:52, Michael S. Tsirkin wrote:
>> At this point how about we revert
>> 7f466032dc9e5a61217f22ea34b2df932786bbfc
>> for this release, and then re-apply a corrected version
>> for the next one?
> 
> If possible, consider we've actually disabled the feature. How about
> just queued those patches for next release?
I'm tossing this series while you and Michael decide how to move forward.

On Mon, Aug 12, 2019 at 10:44:51AM +0800, Jason Wang
wrote:
> 
> On 2019/8/11 ??1:52, Michael S. Tsirkin wrote:
> > On Fri, Aug 09, 2019 at 01:48:42AM -0400, Jason Wang wrote:
> > > Hi all:
> > > 
> > > This series try to fix several issues introduced by meta data
> > > accelreation series. Please review.
> > > 
> > > Changes from V4:
> > > - switch to use spinlock synchronize MMU notifier with accessors
> > > 
> > > Changes from V3:
> > > - remove the unnecessary patch
> > > 
> > > Changes from V2:
> > > - use seqlck helper to synchronize MMU notifier with vhost worker
> > > 
> > > Changes from V1:
> > > - try not use RCU to syncrhonize MMU notifier with vhost worker
> > > - set dirty pages after no readers
> > > - return -EAGAIN only when we find the range is overlapped with
> > >    metadata
> > > 
> > > Jason Wang (9):
> > >    vhost: don't set uaddr for invalid address
> > >    vhost: validate MMU notifier registration
> > >    vhost: fix vhost map leak
> > >    vhost: reset invalidate_count in vhost_set_vring_num_addr()
> > >    vhost: mark dirty pages during map uninit
> > >    vhost: don't do synchronize_rcu() in
vhost_uninit_vq_maps()
> > >    vhost: do not use RCU to synchronize MMU notifier with worker
> > >    vhost: correctly set dirty pages in MMU notifiers callback
> > >    vhost: do not return -EAGAIN for non blocking invalidation too
early
> > > 
> > >   drivers/vhost/vhost.c | 202
+++++++++++++++++++++++++-----------------
> > >   drivers/vhost/vhost.h |   6 +-
> > >   2 files changed, 122 insertions(+), 86 deletions(-)
> > This generally looks more solid.
> > 
> > But this amounts to a significant overhaul of the code.
> > 
> > At this point how about we revert
7f466032dc9e5a61217f22ea34b2df932786bbfc
> > for this release, and then re-apply a corrected version
> > for the next one?
> 
> 
> If possible, consider we've actually disabled the feature. How about
just
> queued those patches for next release?
> 
> Thanks
Sorry if I was unclear. My idea is that
1. I revert the disabled code
2. You send a patch readding it with all the fixes squashed
3. Maybe optimizations on top right away?
4. We queue *that* for next and see what happens.

And the advantage over the patchy approach is that the current patches
are hard to review. E.g.  it's not reasonable to ask RCU guys to review
the whole of vhost for RCU usage but it's much more reasonable to ask
about a specific patch.


-- 
MST

On Mon, Aug 12, 2019 at 05:49:08AM -0400, Michael S. Tsirkin
wrote:
> On Mon, Aug 12, 2019 at 10:44:51AM +0800, Jason Wang wrote:
> > 
> > On 2019/8/11 ??1:52, Michael S. Tsirkin wrote:
> > > On Fri, Aug 09, 2019 at 01:48:42AM -0400, Jason Wang wrote:
> > > > Hi all:
> > > > 
> > > > This series try to fix several issues introduced by meta
data
> > > > accelreation series. Please review.
> > > > 
> > > > Changes from V4:
> > > > - switch to use spinlock synchronize MMU notifier with
accessors
> > > > 
> > > > Changes from V3:
> > > > - remove the unnecessary patch
> > > > 
> > > > Changes from V2:
> > > > - use seqlck helper to synchronize MMU notifier with vhost
worker
> > > > 
> > > > Changes from V1:
> > > > - try not use RCU to syncrhonize MMU notifier with vhost
worker
> > > > - set dirty pages after no readers
> > > > - return -EAGAIN only when we find the range is overlapped
with
> > > >    metadata
> > > > 
> > > > Jason Wang (9):
> > > >    vhost: don't set uaddr for invalid address
> > > >    vhost: validate MMU notifier registration
> > > >    vhost: fix vhost map leak
> > > >    vhost: reset invalidate_count in
vhost_set_vring_num_addr()
> > > >    vhost: mark dirty pages during map uninit
> > > >    vhost: don't do synchronize_rcu() in
vhost_uninit_vq_maps()
> > > >    vhost: do not use RCU to synchronize MMU notifier with
worker
> > > >    vhost: correctly set dirty pages in MMU notifiers
callback
> > > >    vhost: do not return -EAGAIN for non blocking
invalidation too early
> > > > 
> > > >   drivers/vhost/vhost.c | 202
+++++++++++++++++++++++++-----------------
> > > >   drivers/vhost/vhost.h |   6 +-
> > > >   2 files changed, 122 insertions(+), 86 deletions(-)
> > > This generally looks more solid.
> > > 
> > > But this amounts to a significant overhaul of the code.
> > > 
> > > At this point how about we revert
7f466032dc9e5a61217f22ea34b2df932786bbfc
> > > for this release, and then re-apply a corrected version
> > > for the next one?
> > 
> > 
> > If possible, consider we've actually disabled the feature. How
about just
> > queued those patches for next release?
> > 
> > Thanks
> 
> Sorry if I was unclear. My idea is that
> 1. I revert the disabled code
> 2. You send a patch readding it with all the fixes squashed
> 3. Maybe optimizations on top right away?
> 4. We queue *that* for next and see what happens.
> 
> And the advantage over the patchy approach is that the current patches
> are hard to review. E.g.  it's not reasonable to ask RCU guys to review
> the whole of vhost for RCU usage but it's much more reasonable to ask
> about a specific patch.
I think there are other problems here too, I don't like that the use
of mmu notifiers is so different from every other driver, or that GUP
is called under spinlock.

So I favor the revert and try again approach as well. It is hard to
get a clear picture with these endless bug fix patches

Jason

On 2019/8/12 ??5:49, Michael S. Tsirkin wrote:
> On Mon, Aug 12, 2019 at 10:44:51AM +0800, Jason Wang wrote:
>> On 2019/8/11 ??1:52, Michael S. Tsirkin wrote:
>>> On Fri, Aug 09, 2019 at 01:48:42AM -0400, Jason Wang wrote:
>>>> Hi all:
>>>>
>>>> This series try to fix several issues introduced by meta data
>>>> accelreation series. Please review.
>>>>
>>>> Changes from V4:
>>>> - switch to use spinlock synchronize MMU notifier with
accessors
>>>>
>>>> Changes from V3:
>>>> - remove the unnecessary patch
>>>>
>>>> Changes from V2:
>>>> - use seqlck helper to synchronize MMU notifier with vhost
worker
>>>>
>>>> Changes from V1:
>>>> - try not use RCU to syncrhonize MMU notifier with vhost worker
>>>> - set dirty pages after no readers
>>>> - return -EAGAIN only when we find the range is overlapped with
>>>>     metadata
>>>>
>>>> Jason Wang (9):
>>>>     vhost: don't set uaddr for invalid address
>>>>     vhost: validate MMU notifier registration
>>>>     vhost: fix vhost map leak
>>>>     vhost: reset invalidate_count in vhost_set_vring_num_addr()
>>>>     vhost: mark dirty pages during map uninit
>>>>     vhost: don't do synchronize_rcu() in
vhost_uninit_vq_maps()
>>>>     vhost: do not use RCU to synchronize MMU notifier with
worker
>>>>     vhost: correctly set dirty pages in MMU notifiers callback
>>>>     vhost: do not return -EAGAIN for non blocking invalidation
too early
>>>>
>>>>    drivers/vhost/vhost.c | 202
+++++++++++++++++++++++++-----------------
>>>>    drivers/vhost/vhost.h |   6 +-
>>>>    2 files changed, 122 insertions(+), 86 deletions(-)
>>> This generally looks more solid.
>>>
>>> But this amounts to a significant overhaul of the code.
>>>
>>> At this point how about we revert
7f466032dc9e5a61217f22ea34b2df932786bbfc
>>> for this release, and then re-apply a corrected version
>>> for the next one?
>>
>> If possible, consider we've actually disabled the feature. How
about just
>> queued those patches for next release?
>>
>> Thanks
> Sorry if I was unclear. My idea is that
> 1. I revert the disabled code
> 2. You send a patch readding it with all the fixes squashed
> 3. Maybe optimizations on top right away?
> 4. We queue *that* for next and see what happens.
>
> And the advantage over the patchy approach is that the current patches
> are hard to review. E.g.  it's not reasonable to ask RCU guys to review
> the whole of vhost for RCU usage but it's much more reasonable to ask
> about a specific patch.

Ok. Then I agree to revert.

Thanks

On Tue, Aug 20, 2019 at 10:29:32AM +0800, Jason Wang
wrote:
> 
> On 2019/8/20 ??5:08, Michael S. Tsirkin wrote:
> > On Tue, Aug 13, 2019 at 04:12:49PM +0800, Jason Wang wrote:
> > > On 2019/8/12 ??5:49, Michael S. Tsirkin wrote:
> > > > On Mon, Aug 12, 2019 at 10:44:51AM +0800, Jason Wang wrote:
> > > > > On 2019/8/11 ??1:52, Michael S. Tsirkin wrote:
> > > > > > On Fri, Aug 09, 2019 at 01:48:42AM -0400, Jason
Wang wrote:
> > > > > > > Hi all:
> > > > > > > 
> > > > > > > This series try to fix several issues
introduced by meta data
> > > > > > > accelreation series. Please review.
> > > > > > > 
> > > > > > > Changes from V4:
> > > > > > > - switch to use spinlock synchronize MMU
notifier with accessors
> > > > > > > 
> > > > > > > Changes from V3:
> > > > > > > - remove the unnecessary patch
> > > > > > > 
> > > > > > > Changes from V2:
> > > > > > > - use seqlck helper to synchronize MMU
notifier with vhost worker
> > > > > > > 
> > > > > > > Changes from V1:
> > > > > > > - try not use RCU to syncrhonize MMU notifier
with vhost worker
> > > > > > > - set dirty pages after no readers
> > > > > > > - return -EAGAIN only when we find the range
is overlapped with
> > > > > > >      metadata
> > > > > > > 
> > > > > > > Jason Wang (9):
> > > > > > >      vhost: don't set uaddr for invalid
address
> > > > > > >      vhost: validate MMU notifier
registration
> > > > > > >      vhost: fix vhost map leak
> > > > > > >      vhost: reset invalidate_count in
vhost_set_vring_num_addr()
> > > > > > >      vhost: mark dirty pages during map
uninit
> > > > > > >      vhost: don't do synchronize_rcu() in
vhost_uninit_vq_maps()
> > > > > > >      vhost: do not use RCU to synchronize MMU
notifier with worker
> > > > > > >      vhost: correctly set dirty pages in MMU
notifiers callback
> > > > > > >      vhost: do not return -EAGAIN for non
blocking invalidation too early
> > > > > > > 
> > > > > > >     drivers/vhost/vhost.c | 202
+++++++++++++++++++++++++-----------------
> > > > > > >     drivers/vhost/vhost.h |   6 +-
> > > > > > >     2 files changed, 122 insertions(+), 86
deletions(-)
> > > > > > This generally looks more solid.
> > > > > > 
> > > > > > But this amounts to a significant overhaul of the
code.
> > > > > > 
> > > > > > At this point how about we revert
7f466032dc9e5a61217f22ea34b2df932786bbfc
> > > > > > for this release, and then re-apply a corrected
version
> > > > > > for the next one?
> > > > > If possible, consider we've actually disabled the
feature. How about just
> > > > > queued those patches for next release?
> > > > > 
> > > > > Thanks
> > > > Sorry if I was unclear. My idea is that
> > > > 1. I revert the disabled code
> > > > 2. You send a patch readding it with all the fixes squashed
> > > > 3. Maybe optimizations on top right away?
> > > > 4. We queue *that* for next and see what happens.
> > > > 
> > > > And the advantage over the patchy approach is that the
current patches
> > > > are hard to review. E.g.  it's not reasonable to ask RCU
guys to review
> > > > the whole of vhost for RCU usage but it's much more
reasonable to ask
> > > > about a specific patch.
> > > 
> > > Ok. Then I agree to revert.
> > > 
> > > Thanks
> > Great, so please send the following:
> > - revert
> > - squashed and fixed patch
> 
> 
> Just to confirm, do you want me to send a single series or two?
> 
> Thanks
> 
One is fine.

-- 
MST