linux-kernel - Re: [PATCH v2] x86/microcode/intel: replace sync_core() with native_cpuid

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Message-ID: <20200422082741.GA3017981@kroah.com>
Date:   Wed, 22 Apr 2020 10:27:41 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Evalds Iodzevics <evalds.iodzevics@...il.com>
Cc:     linux-kernel@...r.kernel.org, tglx@...utronix.de,
        ben@...adent.org.uk, bp@...e.de, stable@...r.kernel.org
Subject: Re: [PATCH v2] x86/microcode/intel: replace sync_core() with
 native_cpuid_reg(eax)

On Wed, Apr 22, 2020 at 11:17:59AM +0300, Evalds Iodzevics wrote:
> On Intel it is required to do CPUID(1) before reading the microcode
> revision MSR. Current code in 4.4 an 4.9 relies on sync_core() to call
> CPUID, unfortunately on 32 bit machines code inside sync_core() always
> jumps past CPUID instruction as it depends on data structure boot_cpu_data
> witch are not populated correctly so early in boot sequence.
> 
> It depends on:
> commit 5dedade6dfa2 ("x86/CPU: Add native CPUID variants returning a single
> datum")
> 
> This patch is for 4.4 but also should apply to 4.9
> 
> Signed-off-by: Evalds Iodzevics <evalds.iodzevics@...il.com>
> Cc: stable@...r.kernel.org
> ---
>  arch/x86/include/asm/microcode_intel.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Thanks, much better, now queued up.

greg k-h