[libvirt PATCH 16/16] qemu: implement virtiofs hotunplug

[Peter Krempa]

On Wed, Oct 06, 2021 at 09:15:22 +0200, Ján Tomko wrote:
> Signed-off-by: Ján Tomko <jtomko at redhat.com>
> ---
>  src/conf/domain_conf.c   | 24 ++++++++++++
>  src/conf/domain_conf.h   |  2 +
>  src/libvirt_private.syms |  1 +
>  src/qemu/qemu_hotplug.c  | 81 +++++++++++++++++++++++++++++++++++++++-
>  4 files changed, 106 insertions(+), 2 deletions(-)

[...]

> diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
> index f5dad0b829..713da5ebfc 100644
> --- a/src/qemu/qemu_hotplug.c
> +++ b/src/qemu/qemu_hotplug.c
> @@ -5180,6 +5180,45 @@ qemuDomainRemoveRedirdevDevice(virQEMUDriver *driver,
>  }
>  
>  
> +static int
> +qemuDomainRemoveFSDevice(virQEMUDriver *driver,
> +                         virDomainObj *vm,
> +                         virDomainFSDef *fs)
> +{
> +    g_autofree char *charAlias = NULL;
> +    qemuDomainObjPrivate *priv = vm->privateData;
> +    ssize_t idx;
> +    int rc = 0;
> +
> +    VIR_DEBUG("Removing FS device %s from domain %p %s",
> +              fs->info.alias, vm, vm->def->name);
> +
> +    charAlias = qemuDomainGetVhostUserChrAlias(fs->info.alias);
> +
> +    qemuDomainObjEnterMonitor(driver, vm);
> +
> +    if (qemuMonitorDetachCharDev(priv->mon, charAlias) < 0)
> +        rc = -1;

Note that you must not assume here that the check below [1] that allows
only virtio-fs device unplug guards this code too.

The *Remove* code is executed always when we get a 'DEVICE_DELETED'
event from qemu thus also for guest-initiated unplug, which
theoretically can happen also for p9fs device.

> +
> +    if (qemuDomainObjExitMonitor(driver, vm) < 0)
> +        return -1;
> +
> +    virDomainAuditFS(vm, fs, NULL, "detach", rc == 0);
> +
> +    if (rc < 0)
> +        return -1;
> +
> +    if (!fs->sock)
> +        qemuVirtioFSStop(driver, vm, fs);
> +
> +    if ((idx = virDomainFSDefFind(vm->def, fs)) >= 0)
> +        virDomainFSRemove(vm->def, idx);
> +    qemuDomainReleaseDeviceAddress(vm, &fs->info);
> +    virDomainFSDefFree(fs);
> +    return 0;
> +}
> +
> +
>  static void
>  qemuDomainRemoveAuditDevice(virDomainObj *vm,
>                              virDomainDeviceDef *detach,

[...]

> @@ -6020,6 +6066,31 @@ qemuDomainDetachPrepVsock(virDomainObj *vm,
>  }
>  
>  
> +static int
> +qemuDomainDetachPrepFS(virDomainObj *vm,
> +                       virDomainFSDef *match,
> +                       virDomainFSDef **detach)
> +{
> +    ssize_t idx;
> +
> +    if ((idx = virDomainFSDefFind(vm->def, match)) < 0) {
> +        virReportError(VIR_ERR_DEVICE_MISSING, "%s",
> +                       _("matching filesystem not found"));
> +        return -1;
> +    }
> +
> +    if (vm->def->fss[idx]->fsdriver != VIR_DOMAIN_FS_DRIVER_TYPE_VIRTIOFS) {
> +        virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
> +                       _("only virtiofs filesystems can be hotplugged"));
> +        return -1;
> +    }

[1]. This check only guards host-initiated delete.

> +
> +    *detach = vm->def->fss[idx];
> +
> +    return 0;
> +}
> +
> +
>  static int
>  qemuDomainDetachDeviceLease(virQEMUDriver *driver,
>                              virDomainObj *vm,