From: Borislav Petkov <bp@alien8.de>
To: Andi Kleen <andi@firstfloor.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH v1] x86/microcode: Handle negative microcode revisions
Date: Sat, 20 Oct 2018 10:37:42 +0200 [thread overview]
Message-ID: <20181020083742.GA28301@zn.tnic> (raw)
In-Reply-To: <20181020001137.31461-1-andi@firstfloor.org>
On Fri, Oct 19, 2018 at 05:11:37PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
>
> The Intel ucode revision space is unsigned. Inside Intel there are special
s/ucode/microcode/g
> microcodes that have the highest bit set, and they are considered to have
s/microcodes/microcode revisions/g
> a higher revision than any microcodes that don't have this bit set.
>
> The function comparing the microcodes in the Linux driver compares
> u32 with int, which ends up being signed extended to long on 64bit
> systems. This results in these highest bit set microcodes not loading
> because their revision appears negative and smaller than the
> existing microcode.
>
> Change the comparison to unsigned. With that the loading works
> as expected.
>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> ---
> arch/x86/kernel/cpu/microcode/intel.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
> index 16936a24795c..e95cebdd5993 100644
> --- a/arch/x86/kernel/cpu/microcode/intel.c
> +++ b/arch/x86/kernel/cpu/microcode/intel.c
> @@ -93,7 +93,7 @@ static int find_matching_signature(void *mc, unsigned int csig, int cpf)
> /*
> * Returns 1 if update has been found, 0 otherwise.
> */
> -static int has_newer_microcode(void *mc, unsigned int csig, int cpf, int new_rev)
> +static int has_newer_microcode(void *mc, unsigned int csig, int cpf, unsigned new_rev)
I'm gonna let you run checkpatch yourself to find out what the problem
here is.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
next prev parent reply other threads:[~2018-10-20 8:38 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-20 0:11 [PATCH v1] x86/microcode: Handle negative microcode revisions Andi Kleen
2018-10-20 8:37 ` Borislav Petkov [this message]
2018-10-20 13:42 ` Thomas Gleixner
2018-10-20 14:13 ` Andi Kleen
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