[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [RFC PATCH 6/6] arm/xen: Assign xen-virtio DMA ops for virtio devices in Xen guests
On Mon, 18 Apr 2022, Oleksandr wrote: > On 16.04.22 09:07, Christoph Hellwig wrote: > > Hello Christoph > > > On Fri, Apr 15, 2022 at 03:02:45PM -0700, Stefano Stabellini wrote: > > > This makes sense overall. Considering that the swiotlb-xen case and the > > > virtio case are mutually exclusive, I would write it like this: > > Curious question: Why can't the same grant scheme also be used for > > non-virtio devices? I really hate having virtio hooks in the arch > > dma code. Why can't Xen just say in DT/ACPI that grants can be used > > for a given device? [...] > This patch series tries to make things work with "virtio" devices in Xen > system without introducing any modifications to code under drivers/virtio. Actually, I think Christoph has a point. There is nothing inherently virtio specific in this patch series or in the "xen,dev-domid" device tree binding. Assuming a given device is emulated by a Xen backend, it could be used with grants as well. For instance, we could provide an emulated e1000 NIC with a "xen,dev-domid" property in device tree. Linux could use grants with it and the backend could map the grants. It would work the same way as virtio-net/block/etc. Passthrough devices wouldn't have the "xen,dev-domid" property, so no problems. So I think we could easily generalize this work and expand it to any device. We just need to hook on the "xen,dev-domid" device tree property. I think it is just a matter of: - remove the "virtio,mmio" check from xen_is_virtio_device - rename xen_is_virtio_device to something more generic, like xen_is_grants_device - rename xen_virtio_setup_dma_ops to something more generic, like xen_grants_setup_dma_ops And that's pretty much it.
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