Re: [PATCH v19 02/14] KVM: arm64: Fix FGT mapping for HFGITR_EL2.nGCSEPP

On Wed, Aug 12, 2026 at 08:12:01PM +0100, Mark Brown wrote:
> The encoding to trap mapping currently maps a FGT on OP_GCSPOPX to
> HFGITR_EL2.nGCSEPP but as per DDI0601 2026-06 this FGT controls trapping
> of GCSPUSHX and GCSPOPCX, and not the separate GCSPOPX instruction.
> Update the mapping to reflect the architecture.

That information seems to match the one in Arm ARM version M.c.
nGCSEPP, bit [59]
	When FEAT_GCS is implemented:
	Trap execution of any of the following AArch64 instructions at EL1 to EL2:
		• GCSPUSHX.
		• GCSPOPCX.

It looks like GCSPOPX can fault if the record is not a valid entry, but 
there seems to be no trap register bit for that.

Thanks!
Leo, 


> 
> Fixes: 863ac38984a82 ("KVM: arm64: Add missing HFGITR_EL2 FGT entries to nested virt")
> Signed-off-by: Mark Brown <[email protected]>
> ---
>  arch/arm64/kvm/emulate-nested.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
> index 3c82f392845d..b32742d9dd73 100644
> --- a/arch/arm64/kvm/emulate-nested.c
> +++ b/arch/arm64/kvm/emulate-nested.c
> @@ -1432,7 +1432,7 @@ static const struct encoding_to_trap_config encoding_to_fgt[] __initconst = {
>  	SR_FGT(OP_AT_S1E1A, 		HFGITR, ATS1E1A, 1),
>  	SR_FGT(OP_COSP_RCTX, 		HFGITR, COSPRCTX, 1),
>  	SR_FGT(OP_GCSPUSHX, 		HFGITR, nGCSEPP, 0),
> -	SR_FGT(OP_GCSPOPX, 		HFGITR, nGCSEPP, 0),
> +	SR_FGT(OP_GCSPOPCX, 		HFGITR, nGCSEPP, 0),
>  	SR_FGT(OP_GCSPUSHM, 		HFGITR, nGCSPUSHM_EL1, 0),
>  	SR_FGT(OP_BRB_IALL, 		HFGITR, nBRBIALL, 0),
>  	SR_FGT(OP_BRB_INJ, 		HFGITR, nBRBINJ, 0),
> 
> -- 
> 2.47.3
>