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Re: [Qemu-devel] [RFC v2 08/32] postcopy: Add vhost-user flag for postco
From: |
Peter Xu |
Subject: |
Re: [Qemu-devel] [RFC v2 08/32] postcopy: Add vhost-user flag for postcopy and check it |
Date: |
Tue, 29 Aug 2017 14:22:07 +0800 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
On Thu, Aug 24, 2017 at 08:27:06PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
>
> Add a vhost feature flag for postcopy support, and
> use the postcopy notifier to check it before allowing postcopy.
>
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
> contrib/libvhost-user/libvhost-user.h | 1 +
> docs/interop/vhost-user.txt | 10 +++++++++
> hw/virtio/vhost-user.c | 40
> ++++++++++++++++++++++++++++++++++-
> 3 files changed, 50 insertions(+), 1 deletion(-)
>
> diff --git a/contrib/libvhost-user/libvhost-user.h
> b/contrib/libvhost-user/libvhost-user.h
> index acd019876d..95d0d34a28 100644
> --- a/contrib/libvhost-user/libvhost-user.h
> +++ b/contrib/libvhost-user/libvhost-user.h
> @@ -34,6 +34,7 @@ enum VhostUserProtocolFeature {
> VHOST_USER_PROTOCOL_F_MQ = 0,
> VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1,
> VHOST_USER_PROTOCOL_F_RARP = 2,
> + VHOST_USER_PROTOCOL_F_PAGEFAULT = 7,
>
> VHOST_USER_PROTOCOL_F_MAX
> };
> diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
> index 954771d0d8..a279560eb0 100644
> --- a/docs/interop/vhost-user.txt
> +++ b/docs/interop/vhost-user.txt
> @@ -273,6 +273,15 @@ Once the source has finished migration, rings will be
> stopped by
> the source. No further update must be done before rings are
> restarted.
>
> +In postcopy migration the slave is started before all the memory has been
> +received from the source host, and care must be taken to avoid accessing
> pages
> +that have yet to be received. The slave opens a 'userfault'-fd and registers
> +the memory with it; this fd is then passed back over to the master.
> +The master services requests on the userfaultfd for pages that are accessed
> +and when the page is available it performs WAKE ioctl's on the userfaultfd
> +to wake the stalled slave. The client indicates support for this via the
> +VHOST_USER_PROTOCOL_F_PAGEFAULT feature.
> +
> IOMMU support
> -------------
>
> @@ -327,6 +336,7 @@ Protocol features
> #define VHOST_USER_PROTOCOL_F_MTU 4
> #define VHOST_USER_PROTOCOL_F_SLAVE_REQ 5
> #define VHOST_USER_PROTOCOL_F_CROSS_ENDIAN 6
> +#define VHOST_USER_PROTOCOL_F_PAGEFAULT 7
>
> Master message types
> --------------------
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 093675ed98..c51bbd1296 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -17,6 +17,8 @@
> #include "sysemu/kvm.h"
> #include "qemu/error-report.h"
> #include "qemu/sockets.h"
> +#include "migration/migration.h"
> +#include "migration/postcopy-ram.h"
>
> #include <sys/ioctl.h>
> #include <sys/socket.h>
> @@ -34,7 +36,7 @@ enum VhostUserProtocolFeature {
> VHOST_USER_PROTOCOL_F_NET_MTU = 4,
> VHOST_USER_PROTOCOL_F_SLAVE_REQ = 5,
> VHOST_USER_PROTOCOL_F_CROSS_ENDIAN = 6,
> -
> + VHOST_USER_PROTOCOL_F_PAGEFAULT = 7,
> VHOST_USER_PROTOCOL_F_MAX
> };
>
> @@ -123,8 +125,10 @@ static VhostUserMsg m __attribute__ ((unused));
> #define VHOST_USER_VERSION (0x1)
>
> struct vhost_user {
> + struct vhost_dev *dev;
> CharBackend *chr;
> int slave_fd;
> + NotifierWithReturn postcopy_notifier;
> };
>
> static bool ioeventfd_enabled(void)
> @@ -720,6 +724,33 @@ out:
> return ret;
> }
>
> +static int vhost_user_postcopy_notifier(NotifierWithReturn *notifier,
> + void *opaque)
> +{
> + struct PostcopyNotifyData *pnd = opaque;
> + struct vhost_user *u = container_of(notifier, struct vhost_user,
> + postcopy_notifier);
> + struct vhost_dev *dev = u->dev;
> +
> + switch (pnd->reason) {
> + case POSTCOPY_NOTIFY_PROBE:
> + if (!virtio_has_feature(dev->protocol_features,
> + VHOST_USER_PROTOCOL_F_PAGEFAULT)) {
> + /* TODO: Get the device name into this error somehow */
> + error_setg(pnd->errp,
> + "vhost-user backend not capable of postcopy");
> + return -ENOENT;
> + }
> + break;
> +
> + default:
> + /* We ignore notifications we don't know */
> + break;
> + }
> +
> + return 0;
> +}
> +
> static int vhost_user_init(struct vhost_dev *dev, void *opaque)
> {
> uint64_t features, protocol_features;
> @@ -731,6 +762,7 @@ static int vhost_user_init(struct vhost_dev *dev, void
> *opaque)
> u = g_new0(struct vhost_user, 1);
> u->chr = opaque;
> u->slave_fd = -1;
> + u->dev = dev;
> dev->opaque = u;
>
> err = vhost_user_get_features(dev, &features);
> @@ -787,6 +819,9 @@ static int vhost_user_init(struct vhost_dev *dev, void
> *opaque)
> return err;
> }
>
> + u->postcopy_notifier.notify = vhost_user_postcopy_notifier;
> + postcopy_add_notifier(&u->postcopy_notifier);
> +
> return 0;
> }
>
> @@ -797,6 +832,9 @@ static int vhost_user_cleanup(struct vhost_dev *dev)
> assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
>
> u = dev->opaque;
> + if (u->postcopy_notifier.notify) {
Detecting init using the notify hook is slightly strange here for
me... If so, not sure whether we also need:
u->postcopy_notifier.notify = NULL;
Or I'm not sure whether a 2nd call to vhost_user_cleanup() can be
dangerous since postcopy_remove_notifier() will be called twice.
Besides that, the patch looks good to me. Thanks,
> + postcopy_remove_notifier(&u->postcopy_notifier);
> + }
> if (u->slave_fd >= 0) {
> qemu_set_fd_handler(u->slave_fd, NULL, NULL, NULL);
> close(u->slave_fd);
> --
> 2.13.5
>
--
Peter Xu
- [Qemu-devel] [RFC v2 04/32] qemu_ram_block_host_offset, (continued)
- [Qemu-devel] [RFC v2 04/32] qemu_ram_block_host_offset, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 05/32] migration/ram: ramblock_recv_bitmap_test_byte_offset, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 06/32] postcopy: use UFFDIO_ZEROPAGE only when available, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 07/32] postcopy: Add notifier chain, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 08/32] postcopy: Add vhost-user flag for postcopy and check it, Dr. David Alan Gilbert (git), 2017/08/24
- Re: [Qemu-devel] [RFC v2 08/32] postcopy: Add vhost-user flag for postcopy and check it,
Peter Xu <=
- [Qemu-devel] [RFC v2 09/32] vhost-user: Add 'VHOST_USER_POSTCOPY_ADVISE' message, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 10/32] vhub: Support sending fds back to qemu, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 11/32] vhub: Open userfaultfd, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 12/32] postcopy: Allow registering of fd handler, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 13/32] vhost+postcopy: Register shared ufd with postcopy, Dr. David Alan Gilbert (git), 2017/08/24
- [Qemu-devel] [RFC v2 14/32] vhost+postcopy: Transmit 'listen' to client, Dr. David Alan Gilbert (git), 2017/08/24