7:25 a.m.
Peter Krempa (2):
virNetDevTapCreate: Use error message hinting to multiqueue use only
when opening multiple queues
virDomainNetDefCheckABIStability: Consider virtio 'queues' ABI
src/conf/domain_conf.c | 11 +++++++++++
src/util/virnetdevtap.c | 2 +-
2 files changed, 12 insertions(+), 1 deletion(-)
--
2.49.0
7:25 a.m.
New subject: [PATCH 1/2] virNetDevTapCreate: Use error message hinting to multiqueue use only when opening multiple queues
From: Peter Krempa <pkrempa(a)redhat.com>
Due to a logic bug the error message mentioning mult_queue operation
would be mentioned also when a single queue would be opened on an
externally managed tap device.
Adjust the condition to trigger only when multiple queues are in use.
Fixes: f6fb097e11a
Signed-off-by: Peter Krempa <pkrempa(a)redhat.com>
---
src/util/virnetdevtap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/util/virnetdevtap.c b/src/util/virnetdevtap.c
index 1dc77f0f5c..648d095dfc 100644
--- a/src/util/virnetdevtap.c
+++ b/src/util/virnetdevtap.c
@@ -231,7 +231,7 @@ int virNetDevTapCreate(char **ifname,
if (ioctl(fd, TUNSETIFF, &ifr) < 0) {
if (flags & VIR_NETDEV_TAP_CREATE_ALLOW_EXISTING &&
- tapfdSize > 0) {
+ tapfdSize > 1) {
virReportSystemError(errno,
_("Unable to create multiple fds for tap device
%1$s (maybe existing device was created without multi_queue flag)"),
*ifname);
--
2.49.0
7:30 a.m.
New subject: [PATCH 1/2] virNetDevTapCreate: Use error message hinting to
multiqueue use only when opening multiple queues
On Tue, May 13, 2025 at 02:25:50PM +0200, Peter Krempa via Devel wrote:
From: Peter Krempa <pkrempa(a)redhat.com>
Due to a logic bug the error message mentioning mult_queue operation
would be mentioned also when a single queue would be opened on an
externally managed tap device.
Adjust the condition to trigger only when multiple queues are in use.
Fixes: f6fb097e11a
Signed-off-by: Peter Krempa <pkrempa(a)redhat.com>
---
src/util/virnetdevtap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Reviewed-by: Daniel P. Berrangé <berrange(a)redhat.com>
With regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
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7:58 a.m.
New subject: [PATCH 1/2] virNetDevTapCreate: Use error message hinting to
multiqueue use only when opening multiple queues
On a Tuesday in 2025, Peter Krempa via Devel wrote:
From: Peter Krempa <pkrempa(a)redhat.com>
Due to a logic bug the error message mentioning mult_queue operation
multi_queue
would be mentioned also when a single queue would be opened on an
externally managed tap device.
Adjust the condition to trigger only when multiple queues are in use.
Fixes: f6fb097e11a
Signed-off-by: Peter Krempa <pkrempa(a)redhat.com>
---
src/util/virnetdevtap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Jano
7:25 a.m.
New subject: [PATCH 2/2] virDomainNetDefCheckABIStability: Consider virtio 'queues' ABI
From: Peter Krempa <pkrempa(a)redhat.com>
While the queue count itself is not a guest visible property, libvirt
uses it to calculate the 'vectors' property of the 'virtio-net' device
which is ABI.
Since we don't expose control of 'vectors' explicitly, consider
'queues'
ABI.
Signed-off-by: Peter Krempa <pkrempa(a)redhat.com>
---
src/conf/domain_conf.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 542d6ade91..b3b0bd7329 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -20801,6 +20801,17 @@ virDomainNetDefCheckABIStability(virDomainNetDef *src,
return false;
}
+ /* The number of queues is used to calculate the value for 'vectors'
+ * (see qemuBuildNicDevProps) which is machine ABI thus we need to ensure
+ * that the number of queues is kept in sync */
+ if (virDomainNetIsVirtioModel(src) &&
+ (src->driver.virtio.queues != dst->driver.virtio.queues)) {
+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+ _("Target virtio network queue count '%1$d' does not
match source '%2$d'"),
+ dst->driver.virtio.queues, src->driver.virtio.queues);
+ return false;
+ }
+
if (!virDomainVirtioOptionsCheckABIStability(src->virtio, dst->virtio))
return false;
--
2.49.0
7:28 a.m.
New subject: [PATCH 2/2] virDomainNetDefCheckABIStability: Consider virtio
'queues' ABI
On Tue, May 13, 2025 at 02:25:51PM +0200, Peter Krempa via Devel wrote:
From: Peter Krempa <pkrempa(a)redhat.com>
While the queue count itself is not a guest visible property, libvirt
uses it to calculate the 'vectors' property of the 'virtio-net' device
which is ABI.
Since we don't expose control of 'vectors' explicitly, consider
'queues'
ABI.
Signed-off-by: Peter Krempa <pkrempa(a)redhat.com>
---
src/conf/domain_conf.c | 11 +++++++++++
1 file changed, 11 insertions(+)
Reviewed-by: Daniel P. Berrangé <berrange(a)redhat.com>
With regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
7:37 a.m.
New subject: [PATCH 2/2] virDomainNetDefCheckABIStability: Consider virtio
'queues' ABI
On Tue, May 13, 2025 at 13:28:58 +0100, Daniel P. Berrangé wrote:
On Tue, May 13, 2025 at 02:25:51PM +0200, Peter Krempa via Devel
wrote:
> From: Peter Krempa <pkrempa(a)redhat.com>
>
> While the queue count itself is not a guest visible property, libvirt
> uses it to calculate the 'vectors' property of the 'virtio-net'
device
> which is ABI.
>
> Since we don't expose control of 'vectors' explicitly, consider
'queues'
> ABI.
>
> Signed-off-by: Peter Krempa <pkrempa(a)redhat.com>
> ---
> src/conf/domain_conf.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
Per your off-list suggestion I'll be adding a comment to the formula
in qemuBuildNicDevProps which calculates 'vectors' to state that it's
guest ABI and must not change:
if (net->driver.virtio.queues > 1) {
if (net->info.type == VIR_DOMAIN_DEVICE_ADDRESS_TYPE_CCW) {
/* ccw provides a one to one relation of fds to queues and
* does not support the vectors option
*/
mq = VIR_TRISTATE_SWITCH_ON;
} else {
/* As advised at https://www.linux-kvm.org/page/Multiqueue
* we should add vectors=2*N+2 where N is the vhostfdSize
*/
mq = VIR_TRISTATE_SWITCH_ON;
+ /* As 'vectors' is a guest-OS visible property and thus
+ * guest ABI this formula *MUST NOT* change */
vectors = 2 * net->driver.virtio.queues + 2;
}
}
Reviewed-by: Daniel P. Berrangé <berrange(a)redhat.com>
With regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
6
days inactive
6
days old
6 comments
3 participants
participants (3)
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Daniel P. Berrangé -
Ján Tomko -
Peter Krempa