From: Si-Wei Liu <si-wei.liu@oracle.com>
To: Jason Wang <jasowang@redhat.com>
Cc: Eugenio Perez Martin <eperezma@redhat.com>,
mst@redhat.com, xuanzhuo@linux.alibaba.com, dtatulea@nvidia.com,
virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] vhost-vdpa: reset vendor specific mapping to initial state in .release
Date: Thu, 19 Oct 2023 15:57:51 -0700 [thread overview]
Message-ID: <695670fd-6762-42d3-b38c-fb347c8beb1d@oracle.com> (raw)
In-Reply-To: <CACGkMEuX8-T6BhbiqkTfF3NBoxS35zQ=k6Th=h0G5sDz4DV93Q@mail.gmail.com>
On 10/17/2023 10:27 PM, Jason Wang wrote:
>>> If we do
>>> this without a negotiation, IOTLB will not be clear but the Qemu will
>>> try to re-program the IOTLB after reset. Which will break?
>>>
>>> 1) stick the exact old behaviour with just one line of check
>> It's not just one line of check here, the old behavior emulation has to
>> be done as Eugenio illustrated in the other email.
> For vhost-vDPA it's just
>
> if (IOTLB_PERSIST is acked by userspace)
> reset_map()
... and this reset_map in vhost_vdpa_cleanup can't be negotiable
depending on IOTLB_PERSIST. Consider the case where user switches to
virtio-vdpa after an older userspace using vhost-vdpa finished running.
Even with buggy_virtio_reset_map in place it's unwarranted the vendor
IOMMU can get back to the default state, e.g. ending with 1:1
passthrough mapping. If not doing this unconditionally it will get a big
chance to break userspace.
-Siwei
>
> For parent, it's somehow similar:
>
> during .reset()
>
> if (IOTLB_PERSIST is not acked by userspace)
> reset_vendor_mappings()
>
> Anything I missed here?
next prev parent reply other threads:[~2023-10-19 22:58 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-10 9:02 [PATCH 0/4] vdpa: decouple reset of iotlb mapping from device reset Si-Wei Liu
2023-10-10 9:02 ` [PATCH 1/4] vdpa: introduce .reset_map operation callback Si-Wei Liu
2023-10-13 2:49 ` Jason Wang
2023-10-13 7:36 ` Si-Wei Liu
2023-10-16 5:30 ` Jason Wang
2023-10-10 9:02 ` [PATCH 2/4] vhost-vdpa: reset vendor specific mapping to initial state in .release Si-Wei Liu
2023-10-11 11:21 ` Eugenio Perez Martin
2023-10-12 6:18 ` Si-Wei Liu
2023-10-13 3:01 ` Jason Wang
2023-10-13 7:35 ` Si-Wei Liu
2023-10-16 6:32 ` Jason Wang
2023-10-16 11:28 ` Eugenio Perez Martin
2023-10-16 20:30 ` Si-Wei Liu
2023-10-17 2:35 ` Jason Wang
2023-10-17 13:58 ` Eugenio Perez Martin
2023-10-18 4:35 ` Si-Wei Liu
2023-10-18 5:27 ` Jason Wang
2023-10-18 7:00 ` Jason Wang
2023-10-18 8:49 ` Si-Wei Liu
2023-10-19 2:53 ` Jason Wang
2023-10-19 6:46 ` Si-Wei Liu
2023-10-19 8:27 ` Jason Wang
2023-10-19 14:39 ` Eugenio Perez Martin
2023-10-19 22:28 ` Si-Wei Liu
2023-10-20 4:11 ` Jason Wang
2023-10-20 5:57 ` Si-Wei Liu
2023-10-18 8:44 ` Si-Wei Liu
2023-10-18 11:14 ` Eugenio Perez Martin
2023-10-18 23:21 ` Si-Wei Liu
2023-10-19 2:48 ` Jason Wang
2023-10-19 22:57 ` Si-Wei Liu [this message]
2023-10-16 20:10 ` Si-Wei Liu
2023-10-10 9:02 ` [PATCH 3/4] vhost-vdpa: introduce IOTLB_PERSIST backend feature bit Si-Wei Liu
2023-10-10 9:03 ` [PATCH 4/4] vdpa/mlx5: implement .reset_map driver op Si-Wei Liu
2023-10-13 3:04 ` Jason Wang
2023-10-13 7:55 ` Si-Wei Liu
2023-10-11 11:30 ` [PATCH 0/4] vdpa: decouple reset of iotlb mapping from device reset Eugenio Perez Martin
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