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

[Reinette Chatre]

Hi Alexander,

On 10/14/26 1:36 AM, Alexander Graf wrote:
> When L3 CAT gets enabled with rdt=l3cat on Skylake-X stepping 3,
> consecutive kexec boots hang for me during secondary socket bringup.
> Cold boots on the same machine work.

Any insight into where the hang occurs?

What is state of resctrl fs when kexec runs? Is it mounted (with which options)?

Does the boot hang whether resctrl fs is mounted or not?

If resctrl is mounted at time of kexec, has it been set up with different groups?
Does kexec task run from a particular group?
 
Does it make a difference if resctrl fs is unmounted before kexec? As I understand
kexec takes system from resctrl without giving opportunity to reset. There should
be no accumulation of state but system may boot up with settings left over from
previous run. Unmounting resctrl would give opportunity to reset state so that
new kernel can start with clean slate.

What does "during secondary socket bringup" mean exactly? For example, is
the hang when first CPU of second socket is onlined and found to be hanging
in the resctrl online handler?

Thank you.

Reinette