From 7c9e527659c67d4d7b41d9504f93d2d7ee482488 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Mon, 21 Aug 2017 18:58:56 +0200 Subject: 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 --- vl.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'vl.c') diff --git a/vl.c b/vl.c index 9bb5058..a121a65 100644 --- a/vl.c +++ b/vl.c @@ -2893,7 +2893,8 @@ static int machine_set_property(void *opaque, */ static bool object_create_initial(const char *type) { - if (g_str_equal(type, "rng-egd")) { + if (g_str_equal(type, "rng-egd") || + g_str_has_prefix(type, "pr-manager-")) { return false; } -- cgit v1.1