Red Hat Bugzilla – Bug 186520
CONFIG_PCI_MSI is not set to y in installed x86_64 2.6.15 kernel for fc5
Last modified: 2015-01-04 17:26:07 EST
As installed, the .config does not have MSI enabled. It was
enabled for FC4 and FC3 kernels. I can't find any reason in
the release notes or lkml for it being disabled.
Our PathScale InfiniPath product requires MSI in order to function,
and I was surprised to find that I had to install the kernel source
rpm and reconfigure in order for MSI to function.
Was this a deliberate change, and if so, what was the reason?
It caused problems booting on some systems. I don't have the details to hand.
This is a big problem for us.
1. Our cards are the first of probably many which require MSI. MSI was optional
for PCI-X but is required for PCI Express.
2. Other cards like the Mellanox InfiniBand adaptor run faster with MSI enabled
-- see the OpenIB mailing list for discussion about this a while ago.
I have no doubt that some systems have problems with MSI, but they're broken and
will probably get fixed, for example I spent 2 days arguing with the in-house
BIOS team at a Tier 1 computer vendor (a big Red Hat partner) and they finally
agreed that they needed to fix their BIOS so that MSI worked. It turned out to
be a one-line fix...
It appears that the latest FC 4 2.6.16 kernel now has the same issue, that
is, the default 2.6.16 kernel with FC4 yum update now has CONFIG_PCI_MSI=n
It appears that the latest fc4 update kernels (e.g. 2.6.16-1.2108_FC4smp for
x86_64) now has CONFIG_PSI_MSI=y again, and I'm told FC5 has also reverted
to enabling this. Should we expect that to remain true for future
no (it was on as an experiment in fc4, and sneaked into an update
inadvertantly), I'm going to look at enabling it across the board when I rebase