Re: [PATCH] x86/resctrl: Require force for L3 CAT on early Skylake-X

[Luck, Tony]

On Thu, Oct 15, 2026 at 04:58:46PM +0000, Graf (AWS), Alexander wrote:
> I ran a few more experiments. This seems un- or if anything only mildly 
> related to kexec. The real culprit is the microcode version. In my 
> environment, we boot with older microcode (0x1000159), then hot load the 
> latest microcode (0x1000191) and then kexec. In that flow, any write to 
> IA32_L3_QOS_MASK_n stalls the socket that write happens on. I'm 
> collecting a bit more data - including microcode version bisects, early 
> load, etc - and give you a full rundown tomorrow or on Monday, depending 
> on how quickly it finishes.

Alexander,

I don't think that an upstream generic kernel solution is the right
path for your very system-specific issue.

Can't you fix your deployment scripts to look at system stepping and
use that to choose the kernel boot options? I presume that you already
have checks for CPU model number since there are lots of different
options appropriate on a per-model basis. So adding a stepping check
may be easier than battling upstream Linux submission process.

-Tony