Hi, I remember from the dim and distant past (probably a KVM Forum) that one of the touted features of virtio-fs was the ability to get memory efficiency savings by having a direct memory mapping the host pages into the guest address space.
AFAICT the kernel side was merged a while ago, see 22f3787 (virtiofs: set up virtio_fs dax_device) and related. However when investigating what would be needed to support this for Xen guests using virtio-fs we were confused as to what else was needed. There were some patches for the old C daemon: Subject: [PATCH v3 00/26] virtiofs dax patches Date: Wed, 28 Apr 2021 12:00:34 +0100 [thread overview] Message-ID: <[email protected]> although they look like they were never merged and the C version of virtiofsd has since been dropped from tools. Looking at the supporting rust code (vhost_user/message.rs) there are a number of additional messages: /// Virtio-fs draft: map file content into the window. FS_MAP = 6, /// Virtio-fs draft: unmap file content from the window. FS_UNMAP = 7, /// Virtio-fs draft: sync file content. FS_SYNC = 8, /// Virtio-fs draft: perform a read/write from an fd directly to GPA. FS_IO = 9, /// Upper bound of valid commands. MAX_CMD = 10, that don't appear in the current canonical vhost-user reference in the QEMU repository and the QEMU code certainly doesn't have implementations for any of them. So I have some questions: * What VMM/daemon combinations has DAX been tested on? * Isn't it time the vhost-user spec is updated? * Is anyone picking up Dave's patches for the QEMU side of support? Thanks, -- Alex Bennée Virtualisation Tech Lead @ Linaro _______________________________________________ Virtio-fs mailing list [email protected] https://listman.redhat.com/mailman/listinfo/virtio-fs
