Re: [PATCH for-4.15] x86/ucode: Fix microcode payload size for Fam19 processors

[Jan Beulich <jbeulich@xxxxxxxx>]

On 09.02.2021 16:33, Andrew Cooper wrote:
> The original limit provided wasn't accurate.  Blobs are in fact rather larger.
> 
> Fixes: fe36a173d1 ("x86/amd: Initial support for Fam19h processors")
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

> --- a/xen/arch/x86/cpu/microcode/amd.c
> +++ b/xen/arch/x86/cpu/microcode/amd.c
> @@ -111,7 +111,7 @@ static bool verify_patch_size(uint32_t patch_size)
>  #define F15H_MPB_MAX_SIZE 4096
>  #define F16H_MPB_MAX_SIZE 3458
>  #define F17H_MPB_MAX_SIZE 3200
> -#define F19H_MPB_MAX_SIZE 4800
> +#define F19H_MPB_MAX_SIZE 5568

How certain is it that there's not going to be another increase?
And in comparison, how bad would it be if we pulled this upper
limit to something that's at least slightly less of an "odd"
number, e.g. 0x1800, and thus provide some headroom?

Jan