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From: Joerg Roedel <joro@8bytes.org>
To: Christoph Hellwig <hch@lst.de>
Cc: "Michael S . Tsirkin" <mst@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	Jens Axboe <axboe@kernel.dk>,
	virtualization@lists.linux-foundation.org,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	iommu@lists.linux-foundation.org, jfehlig@suse.com,
	jon.grimm@amd.com, brijesh.singh@amd.com
Subject: Re: [PATCH 0/3] Fix virtio-blk issue with SWIOTLB
Date: Thu, 10 Jan 2019 15:26:40 +0100	[thread overview]
Message-ID: <20190110142640.GA5825@8bytes.org> (raw)
In-Reply-To: <20190110135952.GC9255@lst.de>

Hi Christoph,

On Thu, Jan 10, 2019 at 02:59:52PM +0100, Christoph Hellwig wrote:
> On Thu, Jan 10, 2019 at 02:44:30PM +0100, Joerg Roedel wrote:

> > The problem is a limitation of the SWIOTLB implementation,
> > which does not support allocations larger than 256kb. When
> > the virtio-blk driver tries to read/write a block larger
> > than that, the allocation of the dma-handle fails and an IO
> > error is reported.
> 
> s/allocations/mappings/, right?  We don't use the swiotlb
> buffer for the coherent allocations anymore, and I don't think
> virtio-blk uses them anyway.

'Allocation' in the sense that there are address ranges allocated, not
memory, but mappings would also be right.

> I really don't like the fact that we hardcode swiotlb specific.
> This needs to be indirect through the dma ops or struct device,
> as various iommu implementations also have limits (although
> usually much larger ones).

I though about exposing it through DMA-API, but didn't go that route as
I didn't want to extend a generic API for some SWIOTLB specifics. But if
there are more implementations that have a size limitation it makes
certainly sense to put it into the DMA-API. I'll change that in the
next version.

Thanks,

	Joerg

  reply	other threads:[~2019-01-10 14:26 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-10 13:44 [PATCH 0/3] Fix virtio-blk issue with SWIOTLB Joerg Roedel
2019-01-10 13:44 ` Joerg Roedel
2019-01-10 13:44 ` [PATCH 1/3] swiotlb: Export maximum allocation size Joerg Roedel
2019-01-10 13:44 ` Joerg Roedel
2019-01-10 13:44   ` Joerg Roedel
2019-01-10 17:02   ` Konrad Rzeszutek Wilk
2019-01-10 17:02   ` Konrad Rzeszutek Wilk
2019-01-10 17:02     ` Konrad Rzeszutek Wilk
2019-01-11  9:12     ` Joerg Roedel
2019-01-11  9:12     ` Joerg Roedel
2019-01-14 20:49       ` Konrad Rzeszutek Wilk
2019-01-14 21:59         ` Michael S. Tsirkin
2019-01-15 13:05           ` Christoph Hellwig
2019-01-15 13:05           ` Christoph Hellwig
2019-01-14 21:59         ` Michael S. Tsirkin
2019-01-14 20:49       ` Konrad Rzeszutek Wilk
2019-01-10 13:44 ` [PATCH 2/3] virtio: Introduce virtio_max_dma_size() Joerg Roedel
2019-01-10 13:44 ` Joerg Roedel
2019-01-10 13:44 ` [PATCH 3/3] virtio-blk: Consider virtio_max_dma_size() for maximum segment size Joerg Roedel
2019-01-10 13:44 ` Joerg Roedel
2019-01-10 13:59 ` [PATCH 0/3] Fix virtio-blk issue with SWIOTLB Christoph Hellwig
2019-01-10 14:26   ` Joerg Roedel [this message]
2019-01-10 14:26   ` Joerg Roedel
2019-01-10 13:59 ` Christoph Hellwig
2019-01-11  3:29 ` Jason Wang
2019-01-11  9:15   ` Joerg Roedel
2019-01-11  9:15   ` Joerg Roedel
2019-01-14  9:41     ` Jason Wang
2019-01-14  9:50       ` Christoph Hellwig
2019-01-14  9:50       ` Christoph Hellwig
2019-01-14 12:41         ` Jason Wang
2019-01-14 12:41         ` Jason Wang
2019-01-14 18:20           ` Michael S. Tsirkin
2019-01-14 19:09             ` Singh, Brijesh
2019-01-14 19:09               ` Singh, Brijesh
2019-01-14 19:12             ` Robin Murphy
2019-01-14 19:12             ` Robin Murphy
2019-01-14 20:22               ` Christoph Hellwig
2019-01-14 20:22               ` Christoph Hellwig
2019-01-14 20:29               ` Michael S. Tsirkin
2019-01-14 20:29               ` Michael S. Tsirkin
2019-01-14 20:19             ` Christoph Hellwig
2019-01-14 20:48               ` Michael S. Tsirkin
2019-01-14 20:48               ` Michael S. Tsirkin
2019-01-15 13:09                 ` Christoph Hellwig
2019-01-15 13:09                 ` Christoph Hellwig
2019-01-14 20:19             ` Christoph Hellwig
2019-01-15  8:37             ` Joerg Roedel
2019-01-15  8:37             ` Joerg Roedel
2019-01-15 13:20               ` Christoph Hellwig
2019-01-16 14:16                 ` Michael S. Tsirkin
2019-01-16 14:16                 ` Michael S. Tsirkin
2019-01-15 13:20               ` Christoph Hellwig
2019-01-14 18:20           ` Michael S. Tsirkin
2019-01-14  9:41     ` Jason Wang
2019-01-11  3:29 ` Jason Wang
2019-01-10 13:44 Joerg Roedel

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