From 49cb59778a4e6c2d04bb9383a9d97fbbc83f9fce Mon Sep 17 00:00:00 2001 From: Erik Skultety Date: Thu, 7 Jan 2021 16:53:21 +0100 Subject: [PATCH] hostdev: mdev: Lookup mdevs by sysfs path rather than mdev struct MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The lookup didn't do anything apart from comparing the sysfs paths anyway since that's what makes each mdev unique. The most ridiculous usage of the old logic was in virHostdevReAttachMediatedDevices where in order to drop an mdev hostdev from the list of active devices we first had to create a new mdev and use it in the lookup call. Why couldn't we have used the hostdev directly? Because the hostdev and mdev structures are incompatible. The way mdevs are currently removed is via a write to a specific sysfs attribute. If you do it while the machine which has the mdev assigned is running, the write call may block (with a new enough kernel, with older kernels it would return a write error!) until the device is no longer in use which is when the QEMU process exits. The interesting part here comes afterwards when we're cleaning up and call virHostdevReAttachMediatedDevices. The domain doesn't exist anymore, so the list of active hostdevs needs to be updated and the respective hostdevs removed from the list, but remember we had to create an mdev object in the memory in order to find it in the list first which will fail because the write to sysfs had already removed the mdev instance from the host system. And so the next time you try to start the same domain you'll get: "Requested operation is not valid: mediated device is in use by driver QEMU, domain " Fixes: https://gitlab.com/libvirt/libvirt/-/issues/119 Signed-off-by: Erik Skultety Reviewed-by: Ján Tomko --- src/hypervisor/virhostdev.c | 10 ++++------ src/util/virmdev.c | 16 ++++++++-------- src/util/virmdev.h | 4 ++-- 3 files changed, 14 insertions(+), 16 deletions(-) diff --git a/src/hypervisor/virhostdev.c b/src/hypervisor/virhostdev.c index aa3fc8738f..be32a26164 100644 --- a/src/hypervisor/virhostdev.c +++ b/src/hypervisor/virhostdev.c @@ -1975,7 +1975,7 @@ virHostdevReAttachMediatedDevices(virHostdevManagerPtr mgr, virObjectLock(mgr->activeMediatedHostdevs); for (i = 0; i < nhostdevs; i++) { - g_autoptr(virMediatedDevice) mdev = NULL; + g_autofree char *sysfspath = NULL; virMediatedDevicePtr tmp; virDomainHostdevSubsysMediatedDevPtr mdevsrc; virDomainHostdevDefPtr hostdev = hostdevs[i]; @@ -1984,14 +1984,12 @@ virHostdevReAttachMediatedDevices(virHostdevManagerPtr mgr, continue; mdevsrc = &hostdev->source.subsys.u.mdev; - - if (!(mdev = virMediatedDeviceNew(mdevsrc->uuidstr, - mdevsrc->model))) - continue; + sysfspath = virMediatedDeviceGetSysfsPath(mdevsrc->uuidstr); /* Remove from the list only mdevs assigned to @drv_name/@dom_name */ - tmp = virMediatedDeviceListFind(mgr->activeMediatedHostdevs, mdev); + tmp = virMediatedDeviceListFind(mgr->activeMediatedHostdevs, + sysfspath); /* skip inactive devices */ if (!tmp) diff --git a/src/util/virmdev.c b/src/util/virmdev.c index b6df353d56..fc27e9e45d 100644 --- a/src/util/virmdev.c +++ b/src/util/virmdev.c @@ -308,7 +308,7 @@ int virMediatedDeviceListAdd(virMediatedDeviceListPtr list, virMediatedDevicePtr *dev) { - if (virMediatedDeviceListFind(list, *dev)) { + if (virMediatedDeviceListFind(list, (*dev)->path)) { virReportError(VIR_ERR_INTERNAL_ERROR, _("device %s is already in use"), (*dev)->path); return -1; @@ -354,7 +354,7 @@ virMediatedDevicePtr virMediatedDeviceListSteal(virMediatedDeviceListPtr list, virMediatedDevicePtr dev) { - int idx = virMediatedDeviceListFindIndex(list, dev); + int idx = virMediatedDeviceListFindIndex(list, dev->path); return virMediatedDeviceListStealIndex(list, idx); } @@ -370,13 +370,13 @@ virMediatedDeviceListDel(virMediatedDeviceListPtr list, int virMediatedDeviceListFindIndex(virMediatedDeviceListPtr list, - virMediatedDevicePtr dev) + const char *sysfspath) { size_t i; for (i = 0; i < list->count; i++) { - virMediatedDevicePtr other = list->devs[i]; - if (STREQ(other->path, dev->path)) + virMediatedDevicePtr dev = list->devs[i]; + if (STREQ(sysfspath, dev->path)) return i; } return -1; @@ -385,11 +385,11 @@ virMediatedDeviceListFindIndex(virMediatedDeviceListPtr list, virMediatedDevicePtr virMediatedDeviceListFind(virMediatedDeviceListPtr list, - virMediatedDevicePtr dev) + const char *sysfspath) { int idx; - if ((idx = virMediatedDeviceListFindIndex(list, dev)) >= 0) + if ((idx = virMediatedDeviceListFindIndex(list, sysfspath)) >= 0) return list->devs[idx]; else return NULL; @@ -403,7 +403,7 @@ virMediatedDeviceIsUsed(virMediatedDevicePtr dev, const char *drvname, *domname; virMediatedDevicePtr tmp = NULL; - if ((tmp = virMediatedDeviceListFind(list, dev))) { + if ((tmp = virMediatedDeviceListFind(list, dev->path))) { virMediatedDeviceGetUsedBy(tmp, &drvname, &domname); virReportError(VIR_ERR_OPERATION_INVALID, _("mediated device %s is in use by " diff --git a/src/util/virmdev.h b/src/util/virmdev.h index b6563a94fc..e96e5bb8c6 100644 --- a/src/util/virmdev.h +++ b/src/util/virmdev.h @@ -130,11 +130,11 @@ virMediatedDeviceListDel(virMediatedDeviceListPtr list, virMediatedDevicePtr virMediatedDeviceListFind(virMediatedDeviceListPtr list, - virMediatedDevicePtr dev); + const char *sysfspath); int virMediatedDeviceListFindIndex(virMediatedDeviceListPtr list, - virMediatedDevicePtr dev); + const char *sysfspath); int virMediatedDeviceListMarkDevices(virMediatedDeviceListPtr dst,