From: Paolo Bonzini <pbonzini@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>, Peter Xu <peterx@redhat.com>,
qemu devel <qemu-devel@nongnu.org>,
Cornelia Huck <cornelia.huck@de.ibm.com>
Subject: Re: [Qemu-devel] issues of region cache and iommu reset
Date: Thu, 30 Mar 2017 11:02:02 +0200 [thread overview]
Message-ID: <b7e37593-93ed-23c2-7b68-240b46aef9c0@redhat.com> (raw)
In-Reply-To: <20170330002755-mutt-send-email-mst@kernel.org>
On 29/03/2017 23:28, Michael S. Tsirkin wrote:
>> Something like this?
>>
>> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
>> index 03592c5..73e69ac 100644
>> --- a/hw/virtio/virtio.c
>> +++ b/hw/virtio/virtio.c
>> @@ -176,6 +176,10 @@ err_used:
>> address_space_cache_destroy(&new->desc);
>> err_desc:
>> g_free(new);
>> + atomic_rcu_set(&vq->vring.caches, NULL);
>> + if (old) {
>> + call_rcu(old, virtio_free_region_cache, rcu);
>> + }
>> }
>>
>> /* virt queue functions */
> I would be worried about call_rcu here - this means
> something can hang on to and use the old cache,
> and reset really must act as a sync/flush point.
The flush is done later in virtio_reset. Here it's just reacting
asynchronously to the IOMMU reset.
I'm thinking of adding a global generation count for IOMMU mappings, and
forcing an update when the IOMMU mappings have changed.
Paolo
next prev parent reply other threads:[~2017-03-30 9:02 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-29 8:00 [Qemu-devel] issues of region cache and iommu reset Jason Wang
2017-03-29 8:09 ` Paolo Bonzini
2017-03-29 8:37 ` Jason Wang
2017-03-29 8:41 ` Paolo Bonzini
2017-03-29 9:09 ` Jason Wang
2017-03-29 9:11 ` Paolo Bonzini
2017-03-29 9:24 ` Jason Wang
2017-03-29 21:31 ` Michael S. Tsirkin
2017-03-29 8:45 ` Cornelia Huck
2017-03-29 9:18 ` Jason Wang
2017-03-29 11:39 ` Cornelia Huck
2017-03-30 2:14 ` Jason Wang
2017-03-29 21:28 ` Michael S. Tsirkin
2017-03-30 9:02 ` Paolo Bonzini [this message]
2017-03-29 8:16 ` Peter Xu
2017-03-29 21:38 ` Michael S. Tsirkin
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