netdev - Re: [PATCH V2 9/9] vhost: do not return -EAGIAN for non blocking invalidation too early

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Date:   Wed, 31 Jul 2019 18:05:58 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     mst@...hat.com, 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 V2 9/9] vhost: do not return -EAGIAN for non blocking
 invalidation too early


On 2019/7/31 下午5:59, Stefano Garzarella wrote:
> A little typo in the title: s/EAGIAN/EAGAIN
>
> Thanks,
> Stefano


Right, will fix if need respin or Michael can help to fix.

Thanks


>
> On Wed, Jul 31, 2019 at 04:46:55AM -0400, Jason Wang wrote:
>> Instead of returning -EAGAIN unconditionally, we'd better do that only
>> we're sure the range is overlapped with the metadata area.
>>
>> Reported-by: Jason Gunthorpe <jgg@...pe.ca>
>> Fixes: 7f466032dc9e ("vhost: access vq metadata through kernel virtual address")
>> Signed-off-by: Jason Wang <jasowang@...hat.com>
>> ---
>>   drivers/vhost/vhost.c | 32 +++++++++++++++++++-------------
>>   1 file changed, 19 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>> index fc2da8a0c671..96c6aeb1871f 100644
>> --- a/drivers/vhost/vhost.c
>> +++ b/drivers/vhost/vhost.c
>> @@ -399,16 +399,19 @@ static void inline vhost_vq_sync_access(struct vhost_virtqueue *vq)
>>   	smp_mb();
>>   }
>>   
>> -static void vhost_invalidate_vq_start(struct vhost_virtqueue *vq,
>> -				      int index,
>> -				      unsigned long start,
>> -				      unsigned long end)
>> +static int vhost_invalidate_vq_start(struct vhost_virtqueue *vq,
>> +				     int index,
>> +				     unsigned long start,
>> +				     unsigned long end,
>> +				     bool blockable)
>>   {
>>   	struct vhost_uaddr *uaddr = &vq->uaddrs[index];
>>   	struct vhost_map *map;
>>   
>>   	if (!vhost_map_range_overlap(uaddr, start, end))
>> -		return;
>> +		return 0;
>> +	else if (!blockable)
>> +		return -EAGAIN;
>>   
>>   	spin_lock(&vq->mmu_lock);
>>   	++vq->invalidate_count;
>> @@ -423,6 +426,8 @@ static void vhost_invalidate_vq_start(struct vhost_virtqueue *vq,
>>   		vhost_set_map_dirty(vq, map, index);
>>   		vhost_map_unprefetch(map);
>>   	}
>> +
>> +	return 0;
>>   }
>>   
>>   static void vhost_invalidate_vq_end(struct vhost_virtqueue *vq,
>> @@ -443,18 +448,19 @@ static int vhost_invalidate_range_start(struct mmu_notifier *mn,
>>   {
>>   	struct vhost_dev *dev = container_of(mn, struct vhost_dev,
>>   					     mmu_notifier);
>> -	int i, j;
>> -
>> -	if (!mmu_notifier_range_blockable(range))
>> -		return -EAGAIN;
>> +	bool blockable = mmu_notifier_range_blockable(range);
>> +	int i, j, ret;
>>   
>>   	for (i = 0; i < dev->nvqs; i++) {
>>   		struct vhost_virtqueue *vq = dev->vqs[i];
>>   
>> -		for (j = 0; j < VHOST_NUM_ADDRS; j++)
>> -			vhost_invalidate_vq_start(vq, j,
>> -						  range->start,
>> -						  range->end);
>> +		for (j = 0; j < VHOST_NUM_ADDRS; j++) {
>> +			ret = vhost_invalidate_vq_start(vq, j,
>> +							range->start,
>> +							range->end, blockable);
>> +			if (ret)
>> +				return ret;
>> +		}
>>   	}
>>   
>>   	return 0;
>> -- 
>> 2.18.1
>>