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| author | Paolo Bonzini <pbonzini@redhat.com> | 2017-08-21 18:58:56 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2017-09-22 01:06:51 +0200 |
| commit | 7c9e527659c67d4d7b41d9504f93d2d7ee482488 (patch) | |
| tree | 2f604a8ad523e8cf9217b464344900f86d0bbfba /scsi/Makefile.objs | |
| parent | 092aa2fc65b7a35121616aad8f39d47b8f921618 (diff) | |
scsi, file-posix: add support for persistent reservation management
It is a common requirement for virtual machine to send persistent
reservations, but this currently requires either running QEMU with
CAP_SYS_RAWIO, or using out-of-tree patches that let an unprivileged
QEMU bypass Linux's filter on SG_IO commands.
As an alternative mechanism, the next patches will introduce a
privileged helper to run persistent reservation commands without
expanding QEMU's attack surface unnecessarily.
The helper is invoked through a "pr-manager" QOM object, to which
file-posix.c passes SG_IO requests for PERSISTENT RESERVE OUT and
PERSISTENT RESERVE IN commands. For example:
$ qemu-system-x86_64
-device virtio-scsi \
-object pr-manager-helper,id=helper0,path=/var/run/qemu-pr-helper.sock
-drive if=none,id=hd,driver=raw,file.filename=/dev/sdb,file.pr-manager=helper0
-device scsi-block,drive=hd
or:
$ qemu-system-x86_64
-device virtio-scsi \
-object pr-manager-helper,id=helper0,path=/var/run/qemu-pr-helper.sock
-blockdev node-name=hd,driver=raw,file.driver=host_device,file.filename=/dev/sdb,file.pr-manager=helper0
-device scsi-block,drive=hd
Multiple pr-manager implementations are conceivable and possible, though
only one is implemented right now. For example, a pr-manager could:
- talk directly to the multipath daemon from a privileged QEMU
(i.e. QEMU links to libmpathpersist); this makes reservation work
properly with multipath, but still requires CAP_SYS_RAWIO
- use the Linux IOC_PR_* ioctls (they require CAP_SYS_ADMIN though)
- more interestingly, implement reservations directly in QEMU
through file system locks or a shared database (e.g. sqlite)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'scsi/Makefile.objs')
| -rw-r--r-- | scsi/Makefile.objs | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/scsi/Makefile.objs b/scsi/Makefile.objs index 31b82a5a36..5496d2ae6a 100644 --- a/scsi/Makefile.objs +++ b/scsi/Makefile.objs @@ -1 +1,3 @@ block-obj-y += utils.o + +block-obj-$(CONFIG_LINUX) += pr-manager.o |