From: Christoph Hellwig <hch@infradead.org>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: "Alex Williamson" <alex.williamson@redhat.com>,
"Christian König" <christian.koenig@amd.com>,
"Cornelia Huck" <cohuck@redhat.com>,
dri-devel@lists.freedesktop.org, kvm@vger.kernel.org,
linaro-mm-sig@lists.linaro.org, linux-media@vger.kernel.org,
"Sumit Semwal" <sumit.semwal@linaro.org>,
"Daniel Vetter" <daniel.vetter@ffwll.ch>,
"Leon Romanovsky" <leon@kernel.org>,
linux-rdma@vger.kernel.org, "Maor Gottlieb" <maorg@nvidia.com>,
"Oded Gabbay" <ogabbay@kernel.org>
Subject: Re: [PATCH v2 4/4] vfio/pci: Allow MMIO regions to be exported through dma-buf
Date: Tue, 6 Sep 2022 02:51:23 -0700 [thread overview]
Message-ID: <YxcYGzPv022G2vLm@infradead.org> (raw)
In-Reply-To: <4-v2-472615b3877e+28f7-vfio_dma_buf_jgg@nvidia.com>
> +{
> + struct vfio_pci_dma_buf *priv = dmabuf->priv;
> + int rc;
> +
> + rc = pci_p2pdma_distance_many(priv->vdev->pdev, &attachment->dev, 1,
> + true);
This should just use pci_p2pdma_distance.
> + /*
> + * Since the memory being mapped is a device memory it could never be in
> + * CPU caches.
> + */
DMA_ATTR_SKIP_CPU_SYNC doesn't even apply to dma_map_resource, not sure
where this wisdom comes from.
> + dma_addr = dma_map_resource(
> + attachment->dev,
> + pci_resource_start(priv->vdev->pdev, priv->index) +
> + priv->offset,
> + priv->dmabuf->size, dir, DMA_ATTR_SKIP_CPU_SYNC);
This is not how P2P addresses are mapped. You need to use
dma_map_sgtable and have the proper pgmap for it.
The above is just a badly implemented version of the dma-direct
PCI_P2PDMA_MAP_BUS_ADDR case, ignoring mappings through the host
bridge or dma-map-ops interactions.
next prev parent reply other threads:[~2022-09-06 9:51 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-31 23:12 [PATCH v2 0/4] Allow MMIO regions to be exported through dma-buf Jason Gunthorpe
2022-08-31 23:12 ` [PATCH v2 1/4] dma-buf: Add dma_buf_try_get() Jason Gunthorpe
2022-09-01 7:55 ` Christian König
2022-09-06 16:44 ` Jason Gunthorpe
2022-09-06 17:52 ` Christian König
2022-08-31 23:12 ` [PATCH v2 2/4] vfio: Add vfio_device_get() Jason Gunthorpe
2022-08-31 23:12 ` [PATCH v2 3/4] vfio_pci: Do not open code pci_try_reset_function() Jason Gunthorpe
2022-08-31 23:12 ` [PATCH v2 4/4] vfio/pci: Allow MMIO regions to be exported through dma-buf Jason Gunthorpe
2022-09-06 9:51 ` Christoph Hellwig [this message]
2022-09-06 10:38 ` Christian König
2022-09-06 11:48 ` Jason Gunthorpe
2022-09-06 12:34 ` Oded Gabbay
2022-09-06 17:59 ` Jason Gunthorpe
2022-09-06 19:44 ` Oded Gabbay
2022-09-07 12:07 ` Christoph Hellwig
2022-09-07 12:05 ` Christoph Hellwig
2022-09-07 12:33 ` Jason Gunthorpe
2022-09-07 14:29 ` Christoph Hellwig
2022-09-07 14:46 ` Oded Gabbay
2022-09-07 15:23 ` Jason Gunthorpe
2022-09-07 15:32 ` Christoph Hellwig
2022-09-07 16:12 ` Jason Gunthorpe
2022-09-09 13:24 ` Christoph Hellwig
2022-09-09 14:09 ` Jason Gunthorpe
2022-09-07 16:31 ` Robin Murphy
2022-09-07 16:47 ` Jason Gunthorpe
2022-09-07 17:03 ` Dan Williams
2022-09-07 15:01 ` Robin Murphy
2022-09-07 12:03 ` Christoph Hellwig
2022-09-07 15:08 ` Christian König
2022-09-07 15:23 ` Christoph Hellwig
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