From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [RFC 4/4] virtio: Add platform specific DMA API translation for virito devices Date: Fri, 20 Jul 2018 16:15:28 +0300 Message-ID: <20180720160550-mutt-send-email-mst@kernel.org> References: <20180720035941.6844-1-khandual@linux.vnet.ibm.com> <20180720035941.6844-5-khandual@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20180720035941.6844-5-khandual@linux.vnet.ibm.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: Anshuman Khandual Cc: robh@kernel.org, srikar@linux.vnet.ibm.com, benh@kernel.crashing.org, linuxram@us.ibm.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, hch@infradead.org, paulus@samba.org, mpe@ellerman.id.au, joe@perches.com, linuxppc-dev@lists.ozlabs.org, elfring@users.sourceforge.net, haren@linux.vnet.ibm.com, david@gibson.dropbear.id.au List-Id: virtualization@lists.linuxfoundation.org On Fri, Jul 20, 2018 at 09:29:41AM +0530, Anshuman Khandual wrote: >Subject: Re: [RFC 4/4] virtio: Add platform specific DMA API translation for > virito devices s/virito/virtio/ > This adds a hook which a platform can define in order to allow it to > override virtio device's DMA OPS irrespective of whether it has the > flag VIRTIO_F_IOMMU_PLATFORM set or not. We want to use this to do > bounce-buffering of data on the new secure pSeries platform, currently > under development, where a KVM host cannot access all of the memory > space of a secure KVM guest. The host can only access the pages which > the guest has explicitly requested to be shared with the host, thus > the virtio implementation in the guest has to copy data to and from > shared pages. > > With this hook, the platform code in the secure guest can force the > use of swiotlb for virtio buffers, with a back-end for swiotlb which > will use a pool of pre-allocated shared pages. Thus all data being > sent or received by virtio devices will be copied through pages which > the host has access to. > > Signed-off-by: Anshuman Khandual > --- > arch/powerpc/include/asm/dma-mapping.h | 6 ++++++ > arch/powerpc/platforms/pseries/iommu.c | 6 ++++++ > drivers/virtio/virtio.c | 7 +++++++ > 3 files changed, 19 insertions(+) > > diff --git a/arch/powerpc/include/asm/dma-mapping.h b/arch/powerpc/include/asm/dma-mapping.h > index 8fa3945..bc5a9d3 100644 > --- a/arch/powerpc/include/asm/dma-mapping.h > +++ b/arch/powerpc/include/asm/dma-mapping.h > @@ -116,3 +116,9 @@ extern u64 __dma_get_required_mask(struct device *dev); > > #endif /* __KERNEL__ */ > #endif /* _ASM_DMA_MAPPING_H */ > + > +#define platform_override_dma_ops platform_override_dma_ops > + > +struct virtio_device; > + > +extern void platform_override_dma_ops(struct virtio_device *vdev); > diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c > index 06f0296..5773bc7 100644 > --- a/arch/powerpc/platforms/pseries/iommu.c > +++ b/arch/powerpc/platforms/pseries/iommu.c > @@ -38,6 +38,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -1396,3 +1397,8 @@ static int __init disable_multitce(char *str) > __setup("multitce=", disable_multitce); > > machine_subsys_initcall_sync(pseries, tce_iommu_bus_notifier_init); > + > +void platform_override_dma_ops(struct virtio_device *vdev) > +{ > + /* Override vdev->parent.dma_ops if required */ > +} > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > index 6b13987..432c332 100644 > --- a/drivers/virtio/virtio.c > +++ b/drivers/virtio/virtio.c > @@ -168,6 +168,12 @@ EXPORT_SYMBOL_GPL(virtio_add_status); > > const struct dma_map_ops virtio_direct_dma_ops; > > +#ifndef platform_override_dma_ops > +static inline void platform_override_dma_ops(struct virtio_device *vdev) > +{ > +} > +#endif > + > int virtio_finalize_features(struct virtio_device *dev) > { > int ret = dev->config->finalize_features(dev); > @@ -179,6 +185,7 @@ int virtio_finalize_features(struct virtio_device *dev) > if (virtio_has_iommu_quirk(dev)) > set_dma_ops(dev->dev.parent, &virtio_direct_dma_ops); > > + platform_override_dma_ops(dev); Is there a single place where virtio_has_iommu_quirk is called now? If so, we could put this into virtio_has_iommu_quirk then. > if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) > return 0; > > -- > 2.9.3