Re: [PATCH] x86/shstk: Fix possible crash while enabling Shadow Stacks

[Roger Pau Monné <roger@xxxxxxxxxxxxxx>]

On Mon, Oct 19, 2026 at 04:59:59PM +0100, Andrew Cooper wrote:
> Between writing MSR_S_CET.SHSTK_EN and establishing SSP using RSTORSSP or
> SETSSBSY, there must not be any CALL or RET instructions.
> 
> Building Xen with -fno-early-inlining causes wrmsr() to become out-of-line,
> and thus suffers #DF during boot.
> 
> Make the MSR and shstk helpers always_inline.  They ought to have been this
> way all along.
> 
> Reported-by: Roger Pau Monné <roger@xxxxxxxxxxxxxx>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Sorry seems like I'm a bit slow today.  Also worth adding:

Fixes: b60ab42db2f0 ("x86/shstk: Activate Supervisor Shadow Stacks").

Thanks, Roger.