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Date:   Mon, 28 Jan 2019 09:05:26 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Joerg Roedel <joro@8bytes.org>
Cc:     Christoph Hellwig <hch@lst.de>,
        "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, jroedel@suse.de
Subject: Re: [PATCH 5/5] virtio-blk: Consider virtio_max_dma_size() for
 maximum segment size
Message-ID: <20190128080526.GA3874@lst.de>
References: <20190123163049.24863-1-joro@8bytes.org> <20190123163049.24863-6-joro@8bytes.org> <20190123213139.GD9032@lst.de> <20190124084011.GJ32526@8bytes.org> <20190124084221.GB19441@lst.de> <20190124095150.GL32526@8bytes.org>
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On Thu, Jan 24, 2019 at 10:51:51AM +0100, Joerg Roedel wrote:
> On Thu, Jan 24, 2019 at 09:42:21AM +0100, Christoph Hellwig wrote:
> > Yes.  But more importantly it would fix the limit for all other block
> > drivers that set large segment sizes when running over swiotlb.
> 
> True, so it would be something like the diff below? I havn't worked on
> the block layer, so I don't know if that needs additional checks for
> ->dev or anything.

Looks sensible.  Maybe for now we'll just do the virtio-blk case
that triggered it, and we'll do something like this patch for the
next merge window.  We'll also need to apply the same magic to the
DMA boundary.