From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH] virtio_mmio: Set DMA masks appropriately Date: Tue, 10 Jan 2017 16:54:49 +0200 Message-ID: <20170110165221-mutt-send-email-mst@kernel.org> References: <50defbbe87d75db85a9d22f914258975d661208a.1484051089.git.robin.murphy@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <50defbbe87d75db85a9d22f914258975d661208a.1484051089.git.robin.murphy@arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Robin Murphy Cc: will.deacon@arm.com, linux-arm-kernel@lists.infradead.org, luto@kernel.org, virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org On Tue, Jan 10, 2017 at 12:26:01PM +0000, Robin Murphy wrote: > Once DMA API usage is enabled, it becomes apparent that virtio-mmio is > inadvertently relying on the default 32-bit DMA mask, which leads to > problems like rapidly exhausting SWIOTLB bounce buffers. > > Ensure that we set the appropriate 64-bit DMA mask whenever possible, > with the coherent mask suitably limited for the legacy vring as per > a0be1db4304f ("virtio_pci: Limit DMA mask to 44 bits for legacy virtio > devices"). > > Reported-by: Jean-Philippe Brucker > Fixes: b42111382f0e ("virtio_mmio: Use the DMA API if enabled") > Signed-off-by: Robin Murphy > --- > drivers/virtio/virtio_mmio.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c > index 48bfea91dbca..b5c5d49ca598 100644 > --- a/drivers/virtio/virtio_mmio.c > +++ b/drivers/virtio/virtio_mmio.c > @@ -59,6 +59,7 @@ > #define pr_fmt(fmt) "virtio-mmio: " fmt > > #include > +#include > #include > #include > #include > @@ -497,6 +498,7 @@ static int virtio_mmio_probe(struct platform_device *pdev) > struct virtio_mmio_device *vm_dev; > struct resource *mem; > unsigned long magic; > + int rc; > > mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); > if (!mem) > @@ -548,6 +550,14 @@ static int virtio_mmio_probe(struct platform_device *pdev) > if (vm_dev->version == 1) > writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE); > > + rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64)); > + if (rc) > + rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32)); > + else if (vm_dev->version == 1) > + dma_set_coherent_mask(&pdev->dev, DMA_BIT_MASK(32 + PAGE_SHIFT)); That's a very convoluted way to do this, for version 1 you set coherent mask to 64 then override it. why not if (vm_dev->version == 1) { dma_set_mask dma_set_coherent_mask } else { dma_set_mask_and_coherent } if (rc) dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32)); > + if (rc) > + dev_warn(&pdev->dev, "Failed to enable 64-bit or 32-bit DMA. Trying to continue, but this might not work.\n"); > + is there a chance it actually still might work? > platform_set_drvdata(pdev, vm_dev); > > return register_virtio_device(&vm_dev->vdev); > -- > 2.10.2.dirty