Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH RESEND] CPU hotplug,x86 Microcode: Don't request microcode from userspace unnecessarily | Date | Mon, 10 Oct 2011 22:58:02 +0200 |
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On Sunday, October 09, 2011, Srivatsa S. Bhat wrote: > Requesting the microcode from userspace *every time* when onlining CPUs > (during a CPU hotplug operation) is unnecessary. > > So, this patch ensures that once the kernel gets the microcode after booting, > it is not freed nor invalidated when a CPU goes offline, so that it can be > reused when that CPU comes back online, without requesting userspace for it > again. As a result, the CPU hotplug operations become faster as well. > > Tested-by: Borislav Petkov <bp@amd64.org> > Acked-by: Borislav Petkov <bp@amd64.org> > > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Fine by me. I wonder who should take this?
Rafael
> --- > > arch/x86/kernel/microcode_core.c | 9 ++++++++- > 1 files changed, 8 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c > index f924280..33c8a67 100644 > --- a/arch/x86/kernel/microcode_core.c > +++ b/arch/x86/kernel/microcode_core.c > @@ -483,7 +483,14 @@ mc_cpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu) > sysfs_remove_group(&sys_dev->kobj, &mc_attr_group); > pr_debug("CPU%d removed\n", cpu); > break; > - case CPU_DEAD: > + > + /* > + * When a CPU goes offline, don't free up or invalidate the copy of > + * the microcode in kernel memory, so that we can reuse it when the > + * CPU comes back online without unnecessarily requesting the userspace > + * for it again. > + */ > + > case CPU_UP_CANCELED_FROZEN: > /* The CPU refused to come up during a system resume */ > microcode_fini_cpu(cpu); > > > >
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