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Re: [libvirt] [PATCH 2/2] hostdev: fix net config restore error



On Wed, Apr 01, 2015 at 01:35:36PM -0400, Laine Stump wrote:
On 04/01/2015 12:15 PM, Huanle Han wrote:


On 2015年03月31日 17:46, Martin Kletzander wrote:
On Thu, Mar 26, 2015 at 10:23:47PM +0800, Huanle Han wrote:
Fix for such a case:
1. Domain A and B xml contain the same SRIOV net hostdev(<interface
type='hostdev' /> with same pci address).
2. virsh start A (Successfully, and configure the SRIOV net with
custom mac)
3. virsh start B (Fail because of the hostdev used by domain A or other
reason.)
In step 3, 'virHostdevNetConfigRestore' is called for the hostdev
which is still used by domain A. It makes the mac/vlan of the SRIOV net
change.


Makes perfect sense, thanks for finding that out.

Someone else encountered this last month too, and posted a patch:

  https://www.redhat.com/archives/libvir-list/2015-February/msg00394.html

The patch was NACKed because I didn't think the fix was correct
(although it did work)

  https://www.redhat.com/archives/libvir-list/2015-February/msg00976.html

I don't have the time to do a close analysis of this patch right now,
but from the comments it sounds like it addresses the concern that I had
with the previous patch (that it wouldn't be messing with any devices
that were currently not in use by any domain, and hadn't yet been
reached in the setup part). I wanted to point that out now so that
whoever looks at the next version of this patch checks for that.


I must have missed that.  It looks like this series does not have the
issue of the one you've mentioned.



Code Change in this fix:
1. As the pci used by other domain have been removed from
'pcidevs' in previous loop, we only restore the nic config for
the hostdev still in 'pcidevs'(used by this domain)
2. wrap a function 'virHostdevIsPCINetDevice', which detect whether the
hostdev is a pci net device or not.
3. update the comments to make it more clear

Signed-off-by: Huanle Han <hanxueluo gmail com>
<mailto:hanxueluo gmail com>
---
src/util/virhostdev.c | 52
++++++++++++++++++++++++++++++++++++---------------
1 file changed, 37 insertions(+), 15 deletions(-)

diff --git a/src/util/virhostdev.c b/src/util/virhostdev.c
index 83f567d..b04bae2 100644
--- a/src/util/virhostdev.c
+++ b/src/util/virhostdev.c
@@ -350,6 +350,14 @@ virHostdevNetDevice(virDomainHostdevDefPtr
hostdev, char **linkdev,
    return ret;
}

+static int
+virHostdevIsPCINetDevice(virDomainHostdevDefPtr hostdev)
+{
+    return hostdev->mode == VIR_DOMAIN_HOSTDEV_MODE_SUBSYS &&
+        hostdev->source.subsys.type ==
VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_PCI &&
+        hostdev->parent.type == VIR_DOMAIN_DEVICE_NET &&
+        hostdev->parent.data.net <http://parent.data.net>;
+}

static int
virHostdevNetConfigVirtPortProfile(const char *linkdev, int vf,
@@ -481,10 +489,7 @@
virHostdevNetConfigRestore(virDomainHostdevDefPtr hostdev,
    /* This is only needed for PCI devices that have been defined
     * using <interface type='hostdev'>. For all others, it is a NOP.
     */
-    if (hostdev->mode != VIR_DOMAIN_HOSTDEV_MODE_SUBSYS ||
-        hostdev->source.subsys.type !=
VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_PCI ||
-        hostdev->parent.type != VIR_DOMAIN_DEVICE_NET ||
-        !hostdev->parent.data.net <http://parent.data.net>)
+    if (!virHostdevIsPCINetDevice(hostdev))
       return 0;

    isvf = virHostdevIsVirtualFunction(hostdev);
@@ -781,19 +786,20 @@
virHostdevReAttachPCIDevices(virHostdevManagerPtr hostdev_mgr,
        goto cleanup;
    }

-    /* Again 4 loops; mark all devices as inactive before reset
+    /* Here are 4 loops; mark all devices as inactive before reset
     * them and reset all the devices before re-attach.
     * Attach mac and port profile parameters to devices
     */
+
+    /* Loop 1: delete the copy of the dev from pcidevs if it's used by
+     * other domain. Or delete it from activePCIHostDevs if it had
+     * been used by this domain.
+     */
    i = 0;
    while (i < virPCIDeviceListCount(pcidevs)) {
        virPCIDevicePtr dev = virPCIDeviceListGet(pcidevs, i);
        virPCIDevicePtr activeDev = NULL;

-        /* delete the copy of the dev from pcidevs if it's used by
-         * other domain. Or delete it from activePCIHostDevs if it had
-         * been used by this domain.
-         */
        activeDev =
virPCIDeviceListFind(hostdev_mgr->activePCIHostdevs, dev);
        if (activeDev) {
            const char *usedby_drvname;
@@ -814,14 +820,27 @@
virHostdevReAttachPCIDevices(virHostdevManagerPtr hostdev_mgr,
     * pcidevs, but has been removed from activePCIHostdevs.
     */

-    /*
-     * For SRIOV net host devices, unset mac and port profile before
-     * reset and reattach device
+    /* Loop 2: before reset and reattach device,
+     * unset mac and port profile for SRIOV net host devices used
by this domain
     */

The comments were formatted as a sentence, it would be nice to keep it
that way.
Is comment as below OK?
    /*
     * Loop 2: For SRIOV net host devices used by this domain, unset mac
     * and port profile before reset and reattach device
     */


s/reset.*/resetting and reattaching the device./

-    for (i = 0; i < nhostdevs; i++)
-        virHostdevNetConfigRestore(hostdevs[i], hostdev_mgr->stateDir,
-                                   oldStateDir);
+    for (i = 0; i < nhostdevs; i++) {
+        virDomainHostdevDefPtr hostdev = hostdevs[i];

+        if (virHostdevIsPCINetDevice(hostdev)) {
+            virDomainHostdevSubsysPCIPtr pcisrc = &hostdev->source.subsys.u.pci;
+            virPCIDevicePtr dev = NULL;
+            dev = virPCIDeviceNew(pcisrc->addr.domain, pcisrc->addr.bus,
+                                  pcisrc->addr.slot, pcisrc->addr.function);
+

The daemon will crash if this function returns NULL.  There should be
check for that, but it shouldn't be fatal, so we can clean up as much
as possible (see Loop 3 for example on how to handle that).
Is this OK?
            if (dev) {
                if (virPCIDeviceListFind(pcidevs, dev)) {
                    virHostdevNetConfigRestore(hostdev, hostdev_mgr->stateDir,
                                               oldStateDir);
                }
            } else {
                virErrorPtr err = virGetLastError();
                VIR_ERROR(_("Failed to new PCI device: %s"),
                          err ? err->message : _("unknown error"));
                virResetError(err);
            }
            virPCIDeviceFree(dev);


Looks good to me.

+            if (virPCIDeviceListFind(pcidevs, dev)) {
+                virHostdevNetConfigRestore(hostdev,
hostdev_mgr->stateDir,
+                                           oldStateDir);
+            }
+            virPCIDeviceFree(dev);
+        }
+    }
+
+    /* Loop 3: reset pci device used by this domain */
    for (i = 0; i < virPCIDeviceListCount(pcidevs); i++) {
        virPCIDevicePtr dev = virPCIDeviceListGet(pcidevs, i);

@@ -834,6 +853,9 @@
virHostdevReAttachPCIDevices(virHostdevManagerPtr hostdev_mgr,
        }
    }

+    /* Loop 4: reattach pci devices used by this domain
+     * and steal all the devices from pcidevs
+     */
    while (virPCIDeviceListCount(pcidevs) > 0) {
        virPCIDevicePtr dev = virPCIDeviceListStealIndex(pcidevs, 0);
        virHostdevReattachPCIDevice(dev, hostdev_mgr);
--
1.9.1


Other than that, the patch looks fine.

Martin



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