Re: [PATCH] x86/kexec: Fix kexec-reboot with CET active

[David Vrabel <dvrabel@xxxxxxxxxx>]

On 07/03/2022 20:53, Andrew Cooper wrote:
> The kexec_reloc() asm has an indirect jump to relocate onto the identity
> trampoline.  While we clear CET in machine_crash_shutdown(), we fail to clear
> CET for the non-crash path.  This in turn highlights that the same is true of
> resetting the CPUID masking/faulting.
>
> Move both pieces of logic from machine_crash_shutdown() to machine_kexec(),
> the latter being common for all kexec transitions.  Adjust the condition for
> CET being considered active to check in CR4, which is simpler and more robust.
Reviewed-by: David Vrabel <dvrabel@xxxxxxxxxxxx>

> Fixes: 311434bfc9d1 ("x86/setup: Rework MSR_S_CET handling for CET-IBT")
> Fixes: b60ab42db2f0 ("x86/shstk: Activate Supervisor Shadow Stacks")
> Fixes: 5ab9564c6fa1 ("x86/cpu: Context switch cpuid masks and faulting state in 
> context_switch()")
> Reported-by: David Vrabel (XXX which alias to use?)
Amazon, please.

David