diff options
| author | Viresh Kumar <viresh.kumar@linaro.org> | 2023-10-16 12:41:27 +0530 |
|---|---|---|
| committer | Juergen Gross <jgross@suse.com> | 2023-10-16 15:18:33 +0200 |
| commit | f0d7db7b33243d2aeeff14dbdde4ccc0687ef257 (patch) | |
| tree | 93d0eb8908eefb4733f56569717ae35c290eec95 /include/uapi/xen | |
| parent | 9e90e58c11b74c2bddac4b2702cf79d36b981278 (diff) | |
xen: privcmd: Add support for ioeventfd
Virtio guests send VIRTIO_MMIO_QUEUE_NOTIFY notification when they need
to notify the backend of an update to the status of the virtqueue. The
backend or another entity, polls the MMIO address for updates to know
when the notification is sent.
It works well if the backend does this polling by itself. But as we move
towards generic backend implementations, we end up implementing this in
a separate user-space program.
Generally, the Virtio backends are implemented to work with the Eventfd
based mechanism. In order to make such backends work with Xen, another
software layer needs to do the polling and send an event via eventfd to
the backend once the notification from guest is received. This results
in an extra context switch.
This is not a new problem in Linux though. It is present with other
hypervisors like KVM, etc. as well. The generic solution implemented in
the kernel for them is to provide an IOCTL call to pass the address to
poll and eventfd, which lets the kernel take care of polling and raise
an event on the eventfd, instead of handling this in user space (which
involves an extra context switch).
This patch adds similar support for xen.
Inspired by existing implementations for KVM, etc..
This also copies ioreq.h header file (only struct ioreq and related
macros) from Xen's source tree (Top commit 5d84f07fe6bf ("xen/pci: drop
remaining uses of bool_t")).
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/b20d83efba6453037d0c099912813c79c81f7714.1697439990.git.viresh.kumar@linaro.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Diffstat (limited to 'include/uapi/xen')
| -rw-r--r-- | include/uapi/xen/privcmd.h | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/include/uapi/xen/privcmd.h b/include/uapi/xen/privcmd.h index e145bca5105c..8b8c5d1420fe 100644 --- a/include/uapi/xen/privcmd.h +++ b/include/uapi/xen/privcmd.h @@ -110,6 +110,22 @@ struct privcmd_irqfd { __u8 pad[2]; }; +/* For privcmd_ioeventfd::flags */ +#define PRIVCMD_IOEVENTFD_FLAG_DEASSIGN (1 << 0) + +struct privcmd_ioeventfd { + __u64 ioreq; + __u64 ports; + __u64 addr; + __u32 addr_len; + __u32 event_fd; + __u32 vcpus; + __u32 vq; + __u32 flags; + domid_t dom; + __u8 pad[2]; +}; + /* * @cmd: IOCTL_PRIVCMD_HYPERCALL * @arg: &privcmd_hypercall_t @@ -139,5 +155,7 @@ struct privcmd_irqfd { _IOC(_IOC_NONE, 'P', 7, sizeof(struct privcmd_mmap_resource)) #define IOCTL_PRIVCMD_IRQFD \ _IOW('P', 8, struct privcmd_irqfd) +#define IOCTL_PRIVCMD_IOEVENTFD \ + _IOW('P', 9, struct privcmd_ioeventfd) #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */ |