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

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:

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On Wed, Aug 12, 2026 at 08:12:00PM +0100, Mark Brown wrote:

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+	/* 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

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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).

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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.

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Did I get it right? Is there any missing detail here?

That's the idea.

Awesome! FWIW:
Reviewed-by: Leonardo Bras <redacted>