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SubjectRe: patch "x86: MOVE PCI IO ECS code to x86/pci" breaks CPU hotplug
On 21.08.08 15:02:59, Ingo Molnar wrote:
>
> * Jan Beulich <jbeulich@novell.com> wrote:
>
> > Converting __cpuinit functions called out of init_amd() (and similar
> > others) to __init (and making them subject of xxx_initcall() handling
> > isn't valid, as they would no longer be called for hot plugged CPUs.
> >
> > Further, since it's likely that in virtualized environments the MSR
> > write would at best be ignored, I'd also recommend using the
> > fault-safe accessors here *and* check that the bit actually got set
> > before setting PCI_HAS_IO_ECS (one would obviously have to BUG() when
> > hot-plugged CPUs fail to set the bit when those available at boot
> > successfully did so).
>
> hm, which patch is this exactly, and in what tree? It's not upstream nor
> in -tip.

Probably this in the mainline kernel is meant:

commit 3a27dd1ce5de08e21e0266ddf00e6f1f843bfe8b
Author: Robert Richter <robert.richter@amd.com>
Date: Thu Jun 12 20:19:23 2008 +0200

x86: Move PCI IO ECS code to x86/pci

"Form follows function". Code is now where it belongs to.

Signed-off-by: Robert Richter <robert.richter@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

The problem is code like this:

+static int __init enable_pci_io_ecs(void)
+{
+ /* assume all cpus from fam10h have IO ECS */
+ if (boot_cpu_data.x86 < 0x10)
+ return 0;
+ on_each_cpu(enable_pci_io_ecs_per_cpu, NULL, 1, 1);
+ pci_probe |= PCI_HAS_IO_ECS;
+ return 0;
+}

It is only called during the setup and if the cpu is enabled. I intend
to rewrite the cpu setup code using cpu notifiers.

-Robert

--
Advanced Micro Devices, Inc.
Operating System Research Center
email: robert.richter@amd.com



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