[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH RFC 6/6] vhost-user: document migration log
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH RFC 6/6] vhost-user: document migration log |
Date: |
Thu, 23 Jul 2015 18:30:14 +0300 |
On Thu, Jul 23, 2015 at 03:36:43AM +0200, Marc-André Lureau wrote:
> Signed-off-by: Marc-André Lureau <address@hidden>
for some reason I didn't get 5/6.
> ---
> docs/specs/vhost-user.txt | 40 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 40 insertions(+)
>
> diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
> index 0062baa..c2d2e2a 100644
> --- a/docs/specs/vhost-user.txt
> +++ b/docs/specs/vhost-user.txt
> @@ -120,6 +120,7 @@ There are several messages that the master sends with
> file descriptors passed
> in the ancillary data:
>
> * VHOST_SET_MEM_TABLE
> + * VHOST_SET_LOG_BASE (if VHOST_USER_PROTOCOL_F_LOG_SHMFD)
> * VHOST_SET_LOG_FD
> * VHOST_SET_VRING_KICK
> * VHOST_SET_VRING_CALL
> @@ -135,6 +136,11 @@ As older slaves don't support negotiating protocol
> features,
> a feature bit was dedicated for this purpose:
> #define VHOST_USER_F_PROTOCOL_FEATURES 30
>
> +Protocol features
> +-----------------
> +
> +#define VHOST_USER_PROTOCOL_F_LOG_SHMFD 0
> +
> Message types
> -------------
>
> @@ -301,3 +307,37 @@ Message types
> Bits (0-7) of the payload contain the vring index. Bit 8 is the
> invalid FD flag. This flag is set when there is no file descriptor
> in the ancillary data.
> +
> +Migration
> +---------
> +
> +During live migration, the master may need to track the modifications
> +the slave makes to the memory mapped regions. The client should mark
> +the dirty pages in a log. Once it complies to this logging, it may
> +declare VHOST_F_LOG_ALL has a vhost feature.
> +
> +All the modifications to memory pointed by vring "descriptor" should
> +be marked. Modifications to "used" vring should be marked if
> +VHOST_VRING_F_LOG is part of ring's features.
It's device's features I think.
> +
> +Dirty pages are of size:
> +#define VHOST_LOG_PAGE 0x1000
> +
> +The log memory fd is provided in the ancillary data of
> +VHOST_USER_SET_LOG_BASE message when the slave has
> +VHOST_USER_PROTOCOL_F_LOG_SHMFD protocol feature.
> +
> +The size of the log may be computed by using all the known guest
> +addresses. The log covers from address 0 to the maximum of guest
> +regions. In pseudo-code, to mark page at "addr" as dirty:
> +
> +page = addr / VHOST_LOG_PAGE
> +log[page / 8] |= 1 << page % 8
Pls note it must be done atomically.
> +
> +VHOST_USER_SET_LOG_FD is an optional message with an eventfd in
> +ancillary data, it may be used to inform the master that the log has
> +been modified.
> +
> +Once the source has finished migration, VHOST_USER_RESET_OWNER message
> +will be sent by the source. No further update must be done before the
> +destination takes over with new regions & rings.
> --
> 2.4.3
- [Qemu-devel] [PATCH RFC 0/6] vhost-user: add migration log support, Marc-André Lureau, 2015/07/22
- [Qemu-devel] [PATCH RFC 1/6] configure: probe for memfd, Marc-André Lureau, 2015/07/22
- [Qemu-devel] [PATCH RFC 2/6] posix: add linux-only memfd fallback, Marc-André Lureau, 2015/07/22
- [Qemu-devel] [PATCH RFC 3/6] osdep: add memfd helpers, Marc-André Lureau, 2015/07/22
- [Qemu-devel] [PATCH RFC 4/6] vhost: alloc shareable log, Marc-André Lureau, 2015/07/22
- [Qemu-devel] [PATCH RFC 5/6] vhost-user: send log shm fd along with log_base, Marc-André Lureau, 2015/07/22
- [Qemu-devel] [PATCH RFC 6/6] vhost-user: document migration log, Marc-André Lureau, 2015/07/22
- Re: [Qemu-devel] [PATCH RFC 6/6] vhost-user: document migration log,
Michael S. Tsirkin <=