similar to: [PATCH v2 1/2] virtio: Make ARM SMMU workaround more specific

By forcing on DMA API usage for ARM systems, we have inadvertently kicked open a hornets' nest in terms of cache-coherency. Namely that unless the virtio device is explicitly described as capable of coherent DMA by firmware, the DMA APIs on ARM and other DT-based platforms will assume it is non-coherent. This turns out to cause a big problem for the likes of QEMU and kvmtool, which generate

By forcing on DMA API usage for ARM systems, we have inadvertently kicked open a hornets' nest in terms of cache-coherency. Namely that unless the virtio device is explicitly described as capable of coherent DMA by firmware, the DMA APIs on ARM and other DT-based platforms will assume it is non-coherent. This turns out to cause a big problem for the likes of QEMU and kvmtool, which generate

On Wed, Feb 01, 2017 at 08:09:21PM +0200, Michael S. Tsirkin wrote: > On Wed, Feb 01, 2017 at 12:25:57PM +0000, Robin Murphy wrote: > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > index 7e38ed79c3fc..961af25b385c 100644 > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -20,6 +20,7 @@ > >

On Wed, Feb 01, 2017 at 08:09:21PM +0200, Michael S. Tsirkin wrote: > On Wed, Feb 01, 2017 at 12:25:57PM +0000, Robin Murphy wrote: > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > index 7e38ed79c3fc..961af25b385c 100644 > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -20,6 +20,7 @@ > >

Since making use of the DMA API will require the architecture code to have the correct notion of device cache-coherency on architectures like ARM, explicitly call this out in the virtio-mmio DT binding. The ship has sailed for legacy virtio, but let's hope that we can head off any future firmware mishaps. Signed-off-by: Robin Murphy <robin.murphy at arm.com> ---

On 02/01/2017 08:19 PM, Michael S. Tsirkin wrote: > On Wed, Feb 01, 2017 at 06:27:09PM +0000, Will Deacon wrote: >> On Wed, Feb 01, 2017 at 08:09:21PM +0200, Michael S. Tsirkin wrote: >>> On Wed, Feb 01, 2017 at 12:25:57PM +0000, Robin Murphy wrote: >>>> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c >>>> index

On 02/01/2017 08:19 PM, Michael S. Tsirkin wrote: > On Wed, Feb 01, 2017 at 06:27:09PM +0000, Will Deacon wrote: >> On Wed, Feb 01, 2017 at 08:09:21PM +0200, Michael S. Tsirkin wrote: >>> On Wed, Feb 01, 2017 at 12:25:57PM +0000, Robin Murphy wrote: >>>> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c >>>> index

On Thu, Jun 21, 2018 at 08:06:51PM +0100, Jean-Philippe Brucker wrote: > A virtio-mmio node may represent a virtio-iommu device. This is discovered > by the virtio driver at probe time, but the DMA topology isn't > discoverable and must be described by firmware. For DT the standard IOMMU > description is used, as specified in bindings/iommu/iommu.txt and >

On Thu, Jun 21, 2018 at 08:06:51PM +0100, Jean-Philippe Brucker wrote: > A virtio-mmio node may represent a virtio-iommu device. This is discovered > by the virtio driver at probe time, but the DMA topology isn't > discoverable and must be described by firmware. For DT the standard IOMMU > description is used, as specified in bindings/iommu/iommu.txt and >

From: Mark Brown <broonie at linaro.org> According to the README at the existing URL the spec has moved to github so update the documentation to match. Signed-off-by: Mark Brown <broonie at linaro.org> --- Documentation/devicetree/bindings/virtio/mmio.txt | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Documentation/devicetree/bindings/virtio/mmio.txt

From: Mark Brown <broonie at linaro.org> According to the README at the existing URL the spec has moved to github so update the documentation to match. Signed-off-by: Mark Brown <broonie at linaro.org> --- Documentation/devicetree/bindings/virtio/mmio.txt | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Documentation/devicetree/bindings/virtio/mmio.txt

On Tue, Jun 26, 2018 at 11:59 AM Jean-Philippe Brucker <jean-philippe.brucker at arm.com> wrote: > > On 25/06/18 20:27, Rob Herring wrote: > > On Thu, Jun 21, 2018 at 08:06:51PM +0100, Jean-Philippe Brucker wrote: > >> A virtio-mmio node may represent a virtio-iommu device. This is discovered > >> by the virtio driver at probe time, but the DMA topology

On Thu, Feb 02, 2017 at 01:34:03PM +0000, Robin Murphy wrote: > On 02/02/17 11:26, Will Deacon wrote: > > On Wed, Feb 01, 2017 at 09:19:22PM +0200, Michael S. Tsirkin wrote: > >> On Wed, Feb 01, 2017 at 06:27:09PM +0000, Will Deacon wrote: > >>> On Wed, Feb 01, 2017 at 08:09:21PM +0200, Michael S. Tsirkin wrote: > >>>> I'd like to do that instead.

On Thu, Feb 02, 2017 at 01:34:03PM +0000, Robin Murphy wrote: > On 02/02/17 11:26, Will Deacon wrote: > > On Wed, Feb 01, 2017 at 09:19:22PM +0200, Michael S. Tsirkin wrote: > >> On Wed, Feb 01, 2017 at 06:27:09PM +0000, Will Deacon wrote: > >>> On Wed, Feb 01, 2017 at 08:09:21PM +0200, Michael S. Tsirkin wrote: > >>>> I'd like to do that instead.

On Wed, Feb 01, 2017 at 09:19:22PM +0200, Michael S. Tsirkin wrote: > On Wed, Feb 01, 2017 at 06:27:09PM +0000, Will Deacon wrote: > > On Wed, Feb 01, 2017 at 08:09:21PM +0200, Michael S. Tsirkin wrote: > > > I'd like to do that instead. It's fastboot doing the unreasonable thing > > > here and deviating from what every other legacy device without exception >

On Wed, Feb 01, 2017 at 09:19:22PM +0200, Michael S. Tsirkin wrote: > On Wed, Feb 01, 2017 at 06:27:09PM +0000, Will Deacon wrote: > > On Wed, Feb 01, 2017 at 08:09:21PM +0200, Michael S. Tsirkin wrote: > > > I'd like to do that instead. It's fastboot doing the unreasonable thing > > > here and deviating from what every other legacy device without exception >

On Wed, Feb 01, 2017 at 12:25:57PM +0000, Robin Murphy wrote: > By forcing on DMA API usage for ARM systems, we have inadvertently > kicked open a hornets' nest in terms of cache-coherency. Namely that > unless the virtio device is explicitly described as capable of coherent > DMA by firmware, the DMA APIs on ARM and other DT-based platforms will > assume it is non-coherent.

On Wed, Feb 01, 2017 at 12:25:57PM +0000, Robin Murphy wrote: > By forcing on DMA API usage for ARM systems, we have inadvertently > kicked open a hornets' nest in terms of cache-coherency. Namely that > unless the virtio device is explicitly described as capable of coherent > DMA by firmware, the DMA APIs on ARM and other DT-based platforms will > assume it is non-coherent.

On Thu, Feb 02, 2017 at 04:40:49PM +0000, Will Deacon wrote: > On Thu, Feb 02, 2017 at 06:30:28PM +0200, Michael S. Tsirkin wrote: > > I am inclined to say, for 4.10 let's revert > > c7070619f3408d9a0dffbed9149e6f00479cf43b since what it fixes is not a > > regression in 4.10. > > No complaints there, as long as we can keep working to fix this for 4.11 > and

On Thu, Feb 02, 2017 at 04:40:49PM +0000, Will Deacon wrote: > On Thu, Feb 02, 2017 at 06:30:28PM +0200, Michael S. Tsirkin wrote: > > I am inclined to say, for 4.10 let's revert > > c7070619f3408d9a0dffbed9149e6f00479cf43b since what it fixes is not a > > regression in 4.10. > > No complaints there, as long as we can keep working to fix this for 4.11 > and