linux-kernel - Re: [PATCH V5 0/9] Fixes for vhost metadata acceleration

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Message-ID: <663be71f-f96d-cfbc-95a0-da0ac6b82d9f@redhat.com>
Date:   Tue, 13 Aug 2019 16:12:49 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, jgg@...pe.ca
Subject: Re: [PATCH V5 0/9] Fixes for vhost metadata acceleration


On 2019/8/12 下午5:49, Michael S. Tsirkin wrote:
> On Mon, Aug 12, 2019 at 10:44:51AM +0800, Jason Wang wrote:
>> On 2019/8/11 上午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