From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH v2 1/2] virtio_mmio: Set DMA masks appropriately Date: Wed, 11 Jan 2017 01:30:43 +0200 Message-ID: <20170111013032-mutt-send-email-mst@kernel.org> References: <85015f1653eb7e36f992708362b75d1f4391b783.1484070340.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: <85015f1653eb7e36f992708362b75d1f4391b783.1484070340.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 05:51:17PM +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"). > > Cc: Andy Lutomirski > Cc: Michael S. Tsirkin > Reported-by: Jean-Philippe Brucker > Fixes: b42111382f0e ("virtio_mmio: Use the DMA API if enabled") > Signed-off-by: Robin Murphy Acked-by: Michael S. Tsirkin I'mm merge this soon. > --- > drivers/virtio/virtio_mmio.c | 20 +++++++++++++++++++- > 1 file changed, 19 insertions(+), 1 deletion(-) > > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c > index d47a2fcef818..c71fde5fe835 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 > @@ -498,6 +499,7 @@ 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) > @@ -547,9 +549,25 @@ static int virtio_mmio_probe(struct platform_device *pdev) > } > vm_dev->vdev.id.vendor = readl(vm_dev->base + VIRTIO_MMIO_VENDOR_ID); > > - if (vm_dev->version == 1) > + if (vm_dev->version == 1) { > writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE); > > + rc = dma_set_mask(&pdev->dev, DMA_BIT_MASK(64)); > + /* > + * In the legacy case, ensure our coherently-allocated virtio > + * ring will be at an address expressable as a 32-bit PFN. > + */ > + if (!rc) > + dma_set_coherent_mask(&pdev->dev, > + DMA_BIT_MASK(32 + PAGE_SHIFT)); > + } else { > + 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)); > + if (rc) > + dev_warn(&pdev->dev, "Failed to enable 64-bit or 32-bit DMA. Trying to continue, but this might not work.\n"); > + > platform_set_drvdata(pdev, vm_dev); > > return register_virtio_device(&vm_dev->vdev); > -- > 2.10.2.dirty