On Tue, 2 Feb 2016, Andy Lutomirski wrote: > This switches virtio to use the DMA API on Xen and if requested by > module option. > > This fixes virtio on Xen, and it should break anything because it's > off by default on everything except Xen PV on x86. > > To the Xen people: is this okay? If it doesn't work on other Xen > variants (PVH? HVM?), can you submit follow-up patches to fix it? I have been waiting for something like this for a long time: up to now it wasn't possible to use Xen inside a VM with virtio devices. You can add my: Tested-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> > To everyone else: we've waffled on this for way too long. I think > we should to get DMA API implementation in with a conservative > policy like this rather than waiting until we achieve perfection. > I'm tired of carrying these patches around. > > I changed queue allocation around a bit in this version. Per Michael's > request, we no longer use dma_zalloc_coherent in the !dma_api case. > Instead we use alloc_pages_exact, just like the current code does. > This simplifies the ring address accessors, because they can always > load from the dma addr rather than depending on vring_use_dma_api > themselves. > > There's an odd warning in here if the ring's physical address > doesn't fit in a dma_addr_t. This could only possible happen on > really weird configurations in which phys_addr_t is wider than > dma_addr_t. AFAICT this is only possible on i386 PAE systems and on > MIPS, and even there it only happens if highmem is off. But that > means we're safe, since we should never end up with high allocations > on non-highmem systems unless we explicitly ask for them, which we > don't. > > If this is too scary, I can add yet more cruft to avoid it, but > it seems harmless enough to me, and it means that the driver will > be totally clean once all the vring_use_dma_api calls go away. > > Michael, if these survive review, can you stage these in your tree? > Can you also take a look at tools/virtio? I probably broke it, but I > couldn't get it to build without these patches either, so I'm stuck. > > Changes from v6: > - Remove HAVE_DMA_ATTRS and add Acked-by (Cornelia) > - Add some missing signed-off-by lines from me (whoops) > - Rework queue allocation (Michael) > > Changes from v5: > - Typo fixes (David Woodhouse) > - Use xen_domain() to detect Xen (David Vrabel) > - Pass struct vring_virtqueue * into vring_use_dma_api for future proofing > - Removed module parameter (Michael) > > Changes from v4: > - Bake vring_use_dma_api in from the beginning. > - Automatically enable only on Xen. > - Add module parameter. > - Add s390 and alpha DMA API implementations. > - Rebase to 4.5-rc1. > > Changes from v3: > - More big-endian fixes. > - Added better virtio-ring APIs that handle allocation and use them in > virtio-mmio and virtio-pci. > - Switch to Michael's virtio-net patch. > > Changes from v2: > - Fix vring_mapping_error incorrect argument > > Changes from v1: > - Fix an endian conversion error causing a BUG to hit. > - Fix a DMA ordering issue (swiotlb=force works now). > - Minor cleanups. > > Andy Lutomirski (6): > vring: Introduce vring_use_dma_api() > virtio_ring: Support DMA APIs > virtio: Add improved queue allocation API > virtio_mmio: Use the DMA API if enabled > virtio_pci: Use the DMA API if enabled > vring: Use the DMA API on Xen > > Christian Borntraeger (3): > dma: Provide simple noop dma ops > alpha/dma: use common noop dma ops > s390/dma: Allow per device dma ops > > arch/alpha/kernel/pci-noop.c | 46 +--- > arch/s390/Kconfig | 5 +- > arch/s390/include/asm/device.h | 6 +- > arch/s390/include/asm/dma-mapping.h | 6 +- > arch/s390/pci/pci.c | 1 + > arch/s390/pci/pci_dma.c | 4 +- > drivers/virtio/Kconfig | 2 +- > drivers/virtio/virtio_mmio.c | 67 ++---- > drivers/virtio/virtio_pci_common.h | 6 - > drivers/virtio/virtio_pci_legacy.c | 42 ++-- > drivers/virtio/virtio_pci_modern.c | 61 ++--- > drivers/virtio/virtio_ring.c | 439 +++++++++++++++++++++++++++++++----- > include/linux/dma-mapping.h | 2 + > include/linux/virtio.h | 23 +- > include/linux/virtio_ring.h | 35 +++ > lib/Makefile | 1 + > lib/dma-noop.c | 75 ++++++ > tools/virtio/linux/dma-mapping.h | 17 ++ > 18 files changed, 594 insertions(+), 244 deletions(-) > create mode 100644 lib/dma-noop.c > create mode 100644 tools/virtio/linux/dma-mapping.h > > -- > 2.5.0 > _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
