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7c9e527659
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>
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| .. | ||
| block-core.json | ||
| block.json | ||
| char.json | ||
| common.json | ||
| crypto.json | ||
| introspect.json | ||
| Makefile.objs | ||
| migration.json | ||
| net.json | ||
| opts-visitor.c | ||
| qapi-clone-visitor.c | ||
| qapi-dealloc-visitor.c | ||
| qapi-util.c | ||
| qapi-visit-core.c | ||
| qmp-dispatch.c | ||
| qmp-event.c | ||
| qmp-registry.c | ||
| qobject-input-visitor.c | ||
| qobject-output-visitor.c | ||
| rocker.json | ||
| run-state.json | ||
| sockets.json | ||
| string-input-visitor.c | ||
| string-output-visitor.c | ||
| tpm.json | ||
| trace-events | ||
| trace.json | ||
| transaction.json | ||
| ui.json | ||