Re: [PATCH v19 01/14] arm64/gcs: Ensure FGTs for EL1 GCS instructions are disabled

[Leonardo Bras]

On Wed, Aug 19, 2026 at 03:21:31PM +0100, Mark Brown wrote:
> On Wed, Aug 19, 2026 at 02:41:13PM +0100, Leonardo Bras wrote:
> > On Wed, Aug 12, 2026 at 08:12:00PM +0100, Mark Brown wrote:
> 
> > > +	/* Disable traps of GCS instructions at EL1 */
> > > +	orr	x2, x2, #HFGITR_EL2_nGCSEPP_MASK
> > > +	orr	x2, x2, #HFGITR_EL2_nGCSSTR_EL1_MASK
> > > +	orr	x2, x2, #HFGITR_EL2_nGCSPUSHM_EL1_MASK
> 
> > Which I understand to be the way of us saying that EL2 will not interfere 
> > on nor manage those instructions that let software change the entries of 
> > GCS. Is that correct?
> 
> Yes, the goal is to allow EL1 to manage things how it wants (there are
> controls for store and push in GCSCR_EL1 too).
> 
> > As for the asm routine, x2 at this point have nBRBIALL and nBRBINJ already 
> > set, and will be loaded to SYS_HFGITR_EL2 in the next block of 
> > instructions.
> 
> > Did I get it right? Is there any missing detail here?
> 
> That's the idea.


Awesome! FWIW:
Reviewed-by: Leonardo Bras <leo.bras@xxxxxxx>