linux-kernel - Re: [PATCH] x86/microcode/AMD: Increase microcode PATCH_MAX

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Message-ID: <748e8be1-d7e6-c0a3-b83b-a8475873cc4c@kernel.org>
Date:   Fri, 21 Jul 2023 06:47:39 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     John Allen <john.allen@....com>, bp@...en8.de,
        linux-kernel@...r.kernel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, stable@...r.kernel.org
Subject: Re: [PATCH] x86/microcode/AMD: Increase microcode PATCH_MAX_SIZE

On 20. 07. 23, 22:28, John Allen wrote:
> Future AMD cpus will have microcode patches that exceed the current
> limit of three 4K pages. Increase substantially to avoid future size
> increases.

Hi,

so with my current distro (openSUSE TW):
$ zgrep NODES_SHIFT /proc/config.gz
CONFIG_NODES_SHIFT=10

This:

static u8 amd_ucode_patch[MAX_NUMNODES][PATCH_MAX_SIZE];

is now 32M instead of 12M. That is a complete waste on my _one_ node 
system. Can we make amd_ucode_patch dynamic first, depending on 
num_online_nodes()?

> Signed-off-by: John Allen <john.allen@....com>
> Cc: stable@...r.kernel.org
> ---
>   arch/x86/include/asm/microcode_amd.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/microcode_amd.h b/arch/x86/include/asm/microcode_amd.h
> index e6662adf3af4..e3d5f5ae2f46 100644
> --- a/arch/x86/include/asm/microcode_amd.h
> +++ b/arch/x86/include/asm/microcode_amd.h
> @@ -41,7 +41,7 @@ struct microcode_amd {
>   	unsigned int			mpb[];
>   };
>   
> -#define PATCH_MAX_SIZE (3 * PAGE_SIZE)
> +#define PATCH_MAX_SIZE (8 * PAGE_SIZE)
>   
>   #ifdef CONFIG_MICROCODE_AMD
>   extern void __init load_ucode_amd_bsp(unsigned int family);

thanks,
-- 
js
suse labs