[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH V7 1/2] libxl: Add support for Virtio disk configuration
On 22.04.22 12:41, Roger Pau Monné wrote: Hello Roger On Fri, Apr 08, 2022 at 09:21:04PM +0300, Oleksandr Tyshchenko wrote:From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx> This patch adds basic support for configuring and assisting virtio-mmio based virtio-disk backend (emualator) which is intended to run out of Qemu and could be run in any domain. Although the Virtio block device is quite different from traditional Xen PV block device (vbd) from the toolstack's point of view: - as the frontend is virtio-blk which is not a Xenbus driver, nothing written to Xenstore are fetched by the frontend (the vdev is not passed to the frontend) - the ring-ref/event-channel are not used for the backend<->frontend communication, the proposed IPC for Virtio is IOREQ/DM it is still a "block device" and ought to be integrated in existing "disk" handling. So, re-use (and adapt) "disk" parsing/configuration logic to deal with Virtio devices as well. For the immediate purpose and an ability to extend that support for other use-cases in future (Qemu, virtio-pci, etc) perform the following actions: - Add new disk backend type (LIBXL_DISK_BACKEND_OTHER) and reflect that in the configuration - Introduce new disk protocol field to libxl_device_disk struct (with LIBXL_DISK_PROTOCOL_XEN and LIBXL_DISK_PROTOCOL_VIRTIO_MMIO types) and reflect that in the configuration (new "protocol" option with "xen" protocol being default value) - Add new device kind (LIBXL__DEVICE_KIND_VIRTIO_DISK) as current one (LIBXL__DEVICE_KIND_VBD) doesn't fit into Virtio disk model An example of domain configuration for Virtio disk: disk = [ 'phy:/dev/mmcblk0p3, xvda1, backendtype=other, protocol=virtio-mmio'] Nothing has changed for default Xen disk configuration. Please note, this patch is not enough for virtio-disk to work on Xen (Arm), as for every Virtio device (including disk) we need to allocate Virtio MMIO params (IRQ and memory region) and pass them to the backend, also update Guest device-tree. The subsequent patch will add these missing bits. For the current patch, the default "irq" and "base" are just written to the Xenstore. This is not an ideal splitting, but this way we avoid breaking the bisectability. Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx> --- Changes RFC -> V1: - no changes Changes V1 -> V2: - rebase according to the new location of libxl_virtio_disk.c Changes V2 -> V3: - no changes Changes V3 -> V4: - rebase according to the new argument for DEFINE_DEVICE_TYPE_STRUCT Changes V4 -> V5: - split the changes, change the order of the patches - update patch description - don't introduce new "vdisk" configuration option with own parsing logic, re-use Xen PV block "disk" parsing/configuration logic for the virtio-disk - introduce "virtio" flag and document it's usage - add LIBXL_HAVE_DEVICE_DISK_VIRTIO - update libxlu_disk_l.[ch] - drop num_disks variable/MAX_VIRTIO_DISKS - drop Wei's T-b Changes V5 -> V6: - rebase on current staging - use "%"PRIu64 instead of %lu for disk->base in device_disk_add() - update *.gen.go files Changes V6 -> V7: - rebase on current staging - update *.gen.go files and libxlu_disk_l.[ch] files - update patch description - rework significantly to support more flexible configuration and have more generic basic implementation for being able to extend that for other use-cases (virtio-pci, qemu, etc). --- docs/man/xl-disk-configuration.5.pod.in | 37 +- tools/golang/xenlight/helpers.gen.go | 6 + tools/golang/xenlight/types.gen.go | 11 + tools/include/libxl.h | 6 + tools/libs/light/libxl_device.c | 57 +- tools/libs/light/libxl_disk.c | 111 +++- tools/libs/light/libxl_internal.h | 1 + tools/libs/light/libxl_types.idl | 10 + tools/libs/light/libxl_types_internal.idl | 1 + tools/libs/light/libxl_utils.c | 2 + tools/libs/util/libxlu_disk_l.c | 952 +++++++++++++++--------------- tools/libs/util/libxlu_disk_l.h | 2 +- tools/libs/util/libxlu_disk_l.l | 9 + tools/xl/xl_block.c | 11 + 14 files changed, 736 insertions(+), 480 deletions(-) diff --git a/docs/man/xl-disk-configuration.5.pod.in b/docs/man/xl-disk-configuration.5.pod.in index 71d0e86..36c851f 100644 --- a/docs/man/xl-disk-configuration.5.pod.in +++ b/docs/man/xl-disk-configuration.5.pod.in @@ -232,7 +232,7 @@ Specifies the backend implementation to use=item Supported values -phy, qdisk+phy, qdisk, other=item Mandatory @@ -244,11 +244,13 @@ Automatically determine which backend to use. =back -This does not affect the guest's view of the device. It controls-which software implementation of the Xen backend driver is used. +It controls which software implementation of the backend driver is used. +Depending on the "protocol" option this may affect the guest's view +of the device.Not all backend drivers support all combinations of other options.-For example, "phy" does not support formats other than "raw". +For example, "phy" and "other" do not support formats other than "raw" and +"other" does not support protocols other than "virtio-mmio". Normally this option should not be specified, in which case libxl will automatically determine the most suitable backend.@@ -344,8 +346,35 @@ can be used to disable "hole punching" for file based backends whichwere intentionally created non-sparse to avoid fragmentation of the file.+=item B<protocol>=I<PROTOCOL>+ +=over 4 + +=item Description + +Specifies the communication protocol to use for the chosen "backendtype" option + +=item Supported values + +xen, virtio-mmioFrom a user PoV, I think it would be better to just select xen or virtio here, but not the underlying configuration mechanism used to expose the devices to the guest. I got your point. We would likely need to add a different option to select mmio or pci then, but that should be set by default based on architecture/guest type. For example on x86 it should default to pci, while on Arm I guess it will depend on whether the guest has PCI or not? In any case, I think we should offer an option that's selecting between xen or virtio protocol, and the way to expose the configuration of the device shouldn't need to be explicitly selected by the user. ok, for now I will use "xen and virtio" values for the "protocol" option, then internally toolstack will assume that "virtio" really means "virtio-mmio". When there is a need to expand that support to "virtio-pci", we will see how to deal with it from the configuration PoV, probably like you suggested above by adding another option (e.g. "transport") with default values based on the architecture/guest type. Thanks, Roger. -- Regards, Oleksandr Tyshchenko
|
Lists.xenproject.org is hosted with RackSpace, monitoring our |