From: Auger Eric <eric.auger@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Robin Murphy <robin.murphy@arm.com>,
eric.auger.pro@gmail.com, m.szyprowski@samsung.com,
mst@redhat.com, jasowang@redhat.com,
virtualization@lists.linux-foundation.org,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] virtio/virtio_ring: Fix the dma_max_mapping_size call
Date: Thu, 25 Jul 2019 18:32:14 +0200 [thread overview]
Message-ID: <11b7b5e4-2de7-2089-57d2-d0a138f94376@redhat.com> (raw)
In-Reply-To: <20190725130416.GA4992@lst.de>
Hi Christoph, Michael,
On 7/25/19 3:04 PM, Christoph Hellwig wrote:
> On Thu, Jul 25, 2019 at 01:53:49PM +0200, Auger Eric wrote:
>> I am confused: if vring_use_dma_api() returns false if the dma_mask is
>> unset (ie. vring_use_dma_api() returns false), the virtio-blk-pci device
>> will not be able to get translated addresses and won't work properly.
>>
>> The patch above allows the dma api to be used and only influences the
>> max_segment_size and it works properly.
>>
>> So is it normal the dma_mask is unset in my case?
>
> Its not normal. I assume you use virtio-nmio? Due to the mess with
> the dma_mask being a pointer a lot of subsystems forgot to set a dma
> mask up, and oddly enough seem to mostly get away with it.
>
No the issue is encountered with virtio-blk-pci
I think the problem is virtio_max_dma_size() is called from
virtblk_probe (virtio_blk.c) on the virtio<n> device and not the actual
virtio_pci_device which has a dma_mask set. I don't think the virtio<n>
device ever has a dma_mask set.
We do not hit the guest crash on the virtio-net-pci device as the
virtio-net driver does not call virtio_max_dma_size() on the virtio<n>
device.
Does fd1068e1860e ("virtio-blk: Consider virtio_max_dma_size() for
maximum segment size") call virtio_max_dma_size() on the right device?
Thanks
Eric
prev parent reply other threads:[~2019-07-25 16:32 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-22 14:55 [PATCH 0/2] Fix NULL pointer dereference with virtio-blk-pci and virtual IOMMU Eric Auger
2019-07-22 14:55 ` [PATCH 1/2] dma-mapping: Protect dma_addressing_limited against NULL dma_mask Eric Auger
2019-07-22 15:26 ` Christoph Hellwig
2019-07-22 15:46 ` Auger Eric
2019-07-22 14:55 ` [PATCH 2/2] virtio/virtio_ring: Fix the dma_max_mapping_size call Eric Auger
2019-07-22 15:27 ` Christoph Hellwig
2019-07-22 15:39 ` Michael S. Tsirkin
2019-07-22 15:33 ` Michael S. Tsirkin
2019-07-23 15:38 ` Christoph Hellwig
2019-07-23 15:47 ` Michael S. Tsirkin
2019-07-22 15:36 ` Robin Murphy
2019-07-22 15:45 ` Michael S. Tsirkin
2019-07-23 15:38 ` Christoph Hellwig
2019-07-24 22:10 ` Michael S. Tsirkin
2019-07-25 5:25 ` Christoph Hellwig
2019-07-25 11:53 ` Auger Eric
2019-07-25 13:04 ` Christoph Hellwig
2019-07-25 16:32 ` Auger Eric [this message]
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