From: Oleksandr <olekstysh@gmail.com> To: Stefano Stabellini <sstabellini@kernel.org>, Juergen Gross <jgross@suse.com> Cc: Christoph Hellwig <hch@infradead.org>, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Julien Grall <julien@xen.org>, "Michael S. Tsirkin" <mst@redhat.com> Subject: Re: [RFC PATCH 6/6] arm/xen: Assign xen-virtio DMA ops for virtio devices in Xen guests Date: Tue, 19 Apr 2022 15:17:25 +0300 [thread overview] Message-ID: <6a04cc34-fbb3-44d8-c1a4-03bda5b3deb1@gmail.com> (raw) In-Reply-To: <alpine.DEB.2.22.394.2204181202080.915916@ubuntu-linux-20-04-desktop> Hello Stefano, Juergen On 18.04.22 22:11, Stefano Stabellini wrote: > 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. Although the main intention of this series was to enable using virtio devices in Xen guests, I agree that nothing in new DMA ops layer (xen-virtio.c) is virtio specific (at least at the moment). Regarding the whole patch series I am not quite sure, as it uses arch_has_restricted_virtio_memory_access(). > 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. + likely renaming everything in that patch series not to mention virtio (mostly related to xen-virtio.c internals). Stefano, thank you for clarifying Christoph's point. Well, I am not against going this direction. Could we please make a decision on this? @Juergen, what is your opinion? -- Regards, Oleksandr Tyshchenko
WARNING: multiple messages have this Message-ID (diff)
From: Oleksandr <olekstysh@gmail.com> To: Stefano Stabellini <sstabellini@kernel.org>, Juergen Gross <jgross@suse.com> Cc: Christoph Hellwig <hch@infradead.org>, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Julien Grall <julien@xen.org>, "Michael S. Tsirkin" <mst@redhat.com> Subject: Re: [RFC PATCH 6/6] arm/xen: Assign xen-virtio DMA ops for virtio devices in Xen guests Date: Tue, 19 Apr 2022 15:17:25 +0300 [thread overview] Message-ID: <6a04cc34-fbb3-44d8-c1a4-03bda5b3deb1@gmail.com> (raw) In-Reply-To: <alpine.DEB.2.22.394.2204181202080.915916@ubuntu-linux-20-04-desktop> Hello Stefano, Juergen On 18.04.22 22:11, Stefano Stabellini wrote: > 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. Although the main intention of this series was to enable using virtio devices in Xen guests, I agree that nothing in new DMA ops layer (xen-virtio.c) is virtio specific (at least at the moment). Regarding the whole patch series I am not quite sure, as it uses arch_has_restricted_virtio_memory_access(). > 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. + likely renaming everything in that patch series not to mention virtio (mostly related to xen-virtio.c internals). Stefano, thank you for clarifying Christoph's point. Well, I am not against going this direction. Could we please make a decision on this? @Juergen, what is your opinion? -- Regards, Oleksandr Tyshchenko _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-04-19 12:17 UTC|newest] Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-04-14 19:19 [RFC PATCH 0/6] virtio: Solution to restrict memory access under Xen using xen-virtio DMA ops layer Oleksandr Tyshchenko 2022-04-14 19:19 ` Oleksandr Tyshchenko 2022-04-14 19:19 ` [RFC PATCH 1/6] xen/grants: support allocating consecutive grants Oleksandr Tyshchenko 2022-04-14 19:19 ` Oleksandr Tyshchenko 2022-04-14 19:19 ` [RFC PATCH 2/6] virtio: add option to restrict memory access under Xen Oleksandr Tyshchenko 2022-04-14 19:19 ` Oleksandr Tyshchenko 2022-04-14 19:43 ` H. Peter Anvin 2022-04-15 15:20 ` Oleksandr 2022-04-15 15:20 ` Oleksandr 2022-04-15 22:01 ` Stefano Stabellini 2022-04-17 17:02 ` Oleksandr 2022-04-17 17:02 ` Oleksandr 2022-04-18 19:11 ` Stefano Stabellini 2022-04-18 19:11 ` Stefano Stabellini 2022-04-19 6:21 ` Juergen Gross 2022-04-19 6:21 ` Juergen Gross 2022-04-19 6:37 ` Oleksandr 2022-04-19 6:37 ` Oleksandr 2022-04-14 19:19 ` [RFC PATCH 3/6] dt-bindings: xen: Add xen,dev-domid property description for xen-virtio layer Oleksandr Tyshchenko 2022-04-14 19:19 ` [RFC PATCH 3/6] dt-bindings: xen: Add xen, dev-domid " Oleksandr Tyshchenko 2022-04-15 22:01 ` [RFC PATCH 3/6] dt-bindings: xen: Add xen,dev-domid " Stefano Stabellini 2022-04-15 22:01 ` Stefano Stabellini 2022-04-17 17:24 ` Oleksandr 2022-04-17 17:24 ` Oleksandr 2022-04-14 19:19 ` [RFC PATCH 4/6] virtio: Various updates to xen-virtio DMA ops layer Oleksandr Tyshchenko 2022-04-14 19:19 ` Oleksandr Tyshchenko 2022-04-15 22:02 ` Stefano Stabellini 2022-04-15 22:02 ` Stefano Stabellini 2022-04-17 18:21 ` Oleksandr 2022-04-17 18:21 ` Oleksandr 2022-04-18 19:11 ` Stefano Stabellini 2022-04-18 19:11 ` Stefano Stabellini 2022-04-19 6:58 ` Juergen Gross 2022-04-19 6:58 ` Juergen Gross 2022-04-19 7:07 ` Oleksandr 2022-04-19 7:07 ` Oleksandr 2022-04-16 6:05 ` Christoph Hellwig 2022-04-16 6:05 ` Christoph Hellwig 2022-04-17 18:39 ` Oleksandr 2022-04-17 18:39 ` Oleksandr 2022-04-14 19:19 ` [RFC PATCH 5/6] arm/xen: Introduce xen_setup_dma_ops() Oleksandr Tyshchenko 2022-04-14 19:19 ` Oleksandr Tyshchenko 2022-04-15 22:02 ` Stefano Stabellini 2022-04-15 22:02 ` Stefano Stabellini 2022-04-17 18:43 ` Oleksandr 2022-04-17 18:43 ` Oleksandr 2022-04-14 19:19 ` [RFC PATCH 6/6] arm/xen: Assign xen-virtio DMA ops for virtio devices in Xen guests Oleksandr Tyshchenko 2022-04-14 19:19 ` Oleksandr Tyshchenko 2022-04-15 22:02 ` Stefano Stabellini 2022-04-15 22:02 ` Stefano Stabellini 2022-04-16 6:07 ` Christoph Hellwig 2022-04-16 6:07 ` Christoph Hellwig 2022-04-17 21:05 ` Oleksandr 2022-04-17 21:05 ` Oleksandr 2022-04-18 19:11 ` Stefano Stabellini 2022-04-18 19:11 ` Stefano Stabellini 2022-04-19 12:17 ` Oleksandr [this message] 2022-04-19 12:17 ` Oleksandr 2022-04-19 14:48 ` Juergen Gross 2022-04-19 14:48 ` Juergen Gross 2022-04-19 17:11 ` Oleksandr 2022-04-19 17:11 ` Oleksandr 2022-04-20 0:23 ` Stefano Stabellini 2022-04-20 0:23 ` Stefano Stabellini 2022-04-20 9:00 ` Oleksandr 2022-04-20 9:00 ` Oleksandr 2022-04-20 22:49 ` Stefano Stabellini 2022-04-20 22:49 ` Stefano Stabellini 2022-04-17 19:20 ` Oleksandr 2022-04-17 19:20 ` Oleksandr 2022-04-15 7:41 ` [RFC PATCH 0/6] virtio: Solution to restrict memory access under Xen using xen-virtio DMA ops layer Christoph Hellwig 2022-04-15 7:41 ` Christoph Hellwig 2022-04-15 7:41 ` Christoph Hellwig 2022-04-15 10:04 ` Oleksandr 2022-04-15 10:04 ` Oleksandr 2022-04-15 8:44 ` Michael S. Tsirkin 2022-04-15 8:44 ` Michael S. Tsirkin 2022-04-15 8:44 ` Michael S. Tsirkin 2022-04-15 15:29 ` Oleksandr 2022-04-15 15:29 ` Oleksandr
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