linux-kernel - Re: [PATCH v2] x86, AMD: Make cpu_has_amd_erratum() use the correct struct cpuinfo

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Date:	Wed, 7 Aug 2013 08:51:19 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Torsten Kaiser <just.for.lkml@...glemail.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Jacob Shin <jacob.shin@....com>,
	Johannes Hirte <johannes.hirte@....tu-ilmenau.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] x86, AMD: Make cpu_has_amd_erratum() use the correct
 struct cpuinfo_x86

On Tue, Jul 23, 2013 at 07:40:49PM +0200, Torsten Kaiser wrote:
> cpu_has_amd_erratum() is buggy, because it uses the per-cpu cpu_info
> before it is filled by smp_store_boot_cpu_info() / smp_store_cpu_info().
> 
> If early microcode loading is enabled its collect_cpu_info_amd_early() will
> fill ->x86 and so the fallback to boot_cpu_data is not used.
> But ->x86_vendor was not filled and is still 0 == X86_VENDOR_INTEL resulting in 
> no errata fixes getting applied and my system hangs on boot.
> 
> Using cpu_info in cpu_has_amd_erratum() is wrong anyway: Its only caller
> init_amd() will have a struct cpuinfo_x86 as parameter and the set_cpu_bug()
> that is controlled by cpu_has_amd_erratum() also only uses that struct.
> 
> So pass the struct cpuinfo_x86 from init_amd() to cpu_has_amd_erratum() and
> the broken fallback can be dropped.
> 
> I also added an WARN_ON() into the vendor check because init_amd() can only
> be used by AMD CPUs and if the current failure hadn't been silent this bug
> would have been much more obvious.
> 
> V2: At request of Borislav Petkov: BUG_ON -> WARN_ON and subject change
> 
> Signed-off-by: Torsten Kaiser <just.for.lkml@...glemail.com>

Acked-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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