subj: s/virito/virtio/ On Tue, May 22, 2018 at 12:03:17PM +0530, Anshuman Khandual wrote: > This adds a hook which a platform can define in order to allow it to > force the use of the DMA API for all virtio devices even if they don't > have the VIRTIO_F_IOMMU_PLATFORM flag set. 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 <khandual@xxxxxxxxxxxxxxxxxx> > --- > Changes in V2: > > The arch callback has been enabled through an weak symbol defintion > so that it is enabled only for those architectures subscribing to > this new framework. Clarified the patch description. The primary > objective for this RFC has been to get an in principle agreement > on this approach. > > Original V1: > > Original RFC and discussions https://patchwork.kernel.org/patch/10324405/ I re-read that discussion and I'm still unclear on the original question, since I got several apparently conflicting answers. I asked: Why isn't setting VIRTIO_F_IOMMU_PLATFORM on the hypervisor side sufficient? > arch/powerpc/include/asm/dma-mapping.h | 6 ++++++ > arch/powerpc/platforms/pseries/iommu.c | 11 +++++++++++ > drivers/virtio/virtio_ring.c | 10 ++++++++++ > 3 files changed, 27 insertions(+) > > diff --git a/arch/powerpc/include/asm/dma-mapping.h b/arch/powerpc/include/asm/dma-mapping.h > index 8fa3945..056e578 100644 > --- a/arch/powerpc/include/asm/dma-mapping.h > +++ b/arch/powerpc/include/asm/dma-mapping.h > @@ -115,4 +115,10 @@ extern u64 __dma_get_required_mask(struct device *dev); > #define ARCH_HAS_DMA_MMAP_COHERENT > > #endif /* __KERNEL__ */ > + > +#define platform_forces_virtio_dma platform_forces_virtio_dma > + > +struct virtio_device; > + > +extern bool platform_forces_virtio_dma(struct virtio_device *vdev); > #endif /* _ASM_DMA_MAPPING_H */ > diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c > index 06f0296..a2ec15a 100644 > --- a/arch/powerpc/platforms/pseries/iommu.c > +++ b/arch/powerpc/platforms/pseries/iommu.c > @@ -38,6 +38,7 @@ > #include <linux/of.h> > #include <linux/iommu.h> > #include <linux/rculist.h> > +#include <linux/virtio.h> > #include <asm/io.h> > #include <asm/prom.h> > #include <asm/rtas.h> > @@ -1396,3 +1397,13 @@ static int __init disable_multitce(char *str) > __setup("multitce=", disable_multitce); > > machine_subsys_initcall_sync(pseries, tce_iommu_bus_notifier_init); > + > +bool platform_forces_virtio_dma(struct virtio_device *vdev) > +{ > + /* > + * On protected guest platforms, force virtio core to use DMA > + * MAP API for all virtio devices. But there can also be some > + * exceptions for individual devices like virtio balloon. > + */ > + return (of_find_compatible_node(NULL, NULL, "ibm,ultravisor") != NULL); > +} Isn't this kind of slow? vring_use_dma_api is on data path and supposed to be very fast. > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index 21d464a..47ea6c3 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -141,8 +141,18 @@ struct vring_virtqueue { > * unconditionally on data path. > */ > > +#ifndef platform_forces_virtio_dma > +static inline bool platform_forces_virtio_dma(struct virtio_device *vdev) > +{ > + return false; > +} > +#endif > + > static bool vring_use_dma_api(struct virtio_device *vdev) > { > + if (platform_forces_virtio_dma(vdev)) > + return true; > + > if (!virtio_has_iommu_quirk(vdev)) > return true; > > -- > 2.9.3 _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
