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    SubjectRe: [PATCH 00/10] x86, xsave: some code cleanups and reworks
    On Tue, Jul 20, 2010 at 09:46:06PM +0200, Robert Richter wrote:
    > On 20.07.10 15:27:17, Cyrill Gorcunov wrote:
    > > On Tue, Jul 20, 2010 at 08:50:47PM +0200, Robert Richter wrote:
    > > >
    > > > This patch series contains some cleanups and reworks I made during
    > > > code review and feature implementation for upcoming cpus.
    > > >
    > > > Most patches refactor the xsave initialization that is very dependent
    > > > on fpu initialization. This series starts to decouple this a little
    > > > bit as xsave not only supports fpu features. Also this is an attempt
    > > > to ease the xsave interface by making some of the functions and
    > > > variables static.
    > > >
    > > > There is also one patch that removes boot_cpu_id variable, which is
    > > > not really related to xsave. Maybe this should be applied to another
    > > > branch.
    > > >
    > > > The patches are relative to today's tip/x86/xsave branch.
    > > >
    > > > (The patches are small for better review and rebasing.)
    > > >
    > > > -Robert
    > > >
    > >
    > > Hi Robert, I recall there was a thread related to boot_cpu_id and
    > > cpu = 0. Unfortunately I can't find it neither in my mbox nor somewhere
    > > in net at moment.
    >
    > I found this patch:
    >
    > b3572e3 x86/voyager: fix compile breakage caused by dc1e35c6e95e8923cf1d3510438b63c600fee1e2
    >
    > indicating that boot cpu id could be different than 0.
    >

    yeah, I forgot about voyager indeed but seems this is quite specific
    to voyager trick

    > But either this is broken again, or the issue is gone in a different
    > way.
    >
    > > Ie technically speaking -- yes boot_cpu_id will be 0
    > > but perhaps instead of magic !cpu and friends explicit boot_cpu_id might
    > > be better for code reading. It might be is_boot_cpu() macro helper or
    > > so as well.
    > >
    > > Though I don't have strong opinion but for ones who will be
    > > reading the code first time it might be confusing :) Agreed?
    >
    > That's true, but once you know...
    >

    yes, but before you know ;)

    > I could make a follow on patch with an is_boot_cpu() macro. Ingo, what
    > do you think?
    >
    > But first question is, is it always !smp_processor_id()? At least
    > current implementation indicates this:
    >

    I guess so, since it's assigned from boot_cpu_id iirc

    > void __cpuinit identify_secondary_cpu(struct cpuinfo_x86 *c)
    > {
    > BUG_ON(c == &boot_cpu_data);
    > ...
    >
    > with:
    >
    > #define boot_cpu_data cpu_data[0]
    >
    > ... which is valid for 32 and 64 bit.
    >

    I suppose this is just self-protection for "what if something will go
    wrong and this will be called on non-BP cpu".

    > -Robert
    >
    > --
    > Advanced Micro Devices, Inc.
    > Operating System Research Center
    >
    -- Cyrill


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