Re: [RFC-v2 3/6] vhost-scsi: add -vhost-scsi host device for use with tcm-vhost
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From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2012-08-19 08:43:44
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qemu-devel, virtualization
On Sat, Aug 18, 2012 at 05:36:26PM -0700, Nicholas A. Bellinger wrote:
On Sat, 2012-08-18 at 22:12 +0300, Michael S. Tsirkin wrote:quoted
On Tue, Aug 14, 2012 at 01:31:14PM -0700, Nicholas A. Bellinger wrote:quoted
On Mon, 2012-08-13 at 11:53 +0300, Michael S. Tsirkin wrote:quoted
On Mon, Aug 13, 2012 at 08:35:14AM +0000, Nicholas A. Bellinger wrote:quoted
From: Stefan Hajnoczi <redacted><SNIP>quoted
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+static VHostSCSI *vhost_scsi_add(const char *id, const char *wwpn, + uint16_t tpgt) +{ + VHostSCSI *vs = g_malloc0(sizeof(*vs)); + int ret; + + /* TODO set up vhost-scsi device and bind to tcm_vhost/$wwpm/tpgt_$tpgt */ + fprintf(stderr, "wwpn = \"%s\" tpgt = \"%u\"\n", id, tpgt); + + ret = vhost_dev_init(&vs->dev, -1, "/dev/vhost-scsi", false);This -1 is a hack. You need to support passing in fd from the monitor, and pass it here.Mmm, looking at how vhost_net_init + tap.c does this, but am not quite what fd needs to be propagated up for virtio-scsi -> vhost-scsi.. Can you please elaborate on this one a bit more..?The idea is to allow running as a user without access to /dev/vhost-scsi. For this, allow passing in the fd of /dev/vhost-scsi through unix domain sockets.Ah, that is a pretty neat trick.. So for vhost-scsi code, this would mean something along the lines of the following, yes..?
Yes but with one correction. See below.
Thanks MST!
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diff --git a/hw/vhost-scsi.c b/hw/vhost-scsi.c index 4206a75..8af8758 100644 --- a/hw/vhost-scsi.c +++ b/hw/vhost-scsi.c@@ -21,6 +21,7 @@ struct VHostSCSI { const char *id; const char *wwpn; uint16_t tpgt; + int vhostfd; struct vhost_dev dev; struct vhost_virtqueue vqs[VHOST_SCSI_VQ_NUM]; QLIST_ENTRY(VHostSCSI) list;@@ -114,13 +115,32 @@ void vhost_scsi_stop(VHostSCSI *vs, VirtIODevice *vdev) } static VHostSCSI *vhost_scsi_add(const char *id, const char *wwpn, - uint16_t tpgt) + uint16_t tpgt, const char *vhostfd_str) { - VHostSCSI *vs = g_malloc0(sizeof(*vs)); + VHostSCSI *vs; int ret; + vs = g_malloc0(sizeof(*vs)); + if (!vs) { + error_report("vhost-scsi: unable to allocate *vs\n"); + return NULL; + } + vs->vhostfd = -1; + + if (vhostfd_str) { + if (!qemu_isdigit(vhostfd_str[0])) { + error_report("vhost-scsi: passed vhostfd value is not a digit\n"); + return NULL;
This let you use an fd which was open at exec but does not allow for fd to be open later in case device is hot-plugged. See net_handle_fd_param - I think you can just rename it qemu_handle_fd_param to avoid code duplication.
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+ } + + vs->vhostfd = qemu_parse_fd(vhostfd_str); + if (vs->vhostfd == -1) { + error_report("vhost-scsi: unable to parse vs->vhostfd\n"); + return NULL; + } + } /* TODO set up vhost-scsi device and bind to tcm_vhost/$wwpm/tpgt_$tpgt */ - ret = vhost_dev_init(&vs->dev, -1, "/dev/vhost-scsi", false); + ret = vhost_dev_init(&vs->dev, vs->vhostfd, "/dev/vhost-scsi", false); if (ret < 0) { error_report("vhost-scsi: vhost initialization failed: %s\n", strerror(-ret));@@ -140,7 +160,7 @@ static VHostSCSI *vhost_scsi_add(const char *id, const char *wwpn, VHostSCSI *vhost_scsi_add_opts(QemuOpts *opts) { const char *id; - const char *wwpn; + const char *wwpn, *vhostfd; uint64_t tpgt; id = qemu_opts_id(opts);@@ -164,6 +184,7 @@ VHostSCSI *vhost_scsi_add_opts(QemuOpts *opts) error_report("vhost-scsi: \"%s\" needs a 16-bit tpgt\n", id); return NULL; } + vhostfd = qemu_opt_get(opts, "vhostfd"); - return vhost_scsi_add(id, wwpn, tpgt); + return vhost_scsi_add(id, wwpn, tpgt, vhostfd); }diff --git a/qemu-config.c b/qemu-config.c index 33399ea..2d4884c 100644 --- a/qemu-config.c +++ b/qemu-config.c@@ -636,6 +636,9 @@ QemuOptsList qemu_vhost_scsi_opts = { }, { .name = "tpgt", .type = QEMU_OPT_NUMBER, + }, { + .name = "vhostfd", + .type = QEMU_OPT_STRING, }, { /* end of list */ } },