On Mon, Dec 9, 2024 at 8:36 PM Mark Brown <broonie@xxxxxxxxxx> wrote: > > On Mon, Dec 09, 2024 at 06:52:37PM +0800, Weizhao Ouyang wrote: > > > When using svcr_in to check ZA and Streaming Mode, we should make sure > > that the value in x2 is correct, otherwise it may trigger an Illegal > > instruction if FEAT_SVE and !FEAT_SME. > > > // Set SVCR if we're doing SME > > - cbz x1, 1f > > adrp x2, svcr_in > > ldr x2, [x2, :lo12:svcr_in] > > + cbz x1, 1f > > msr S3_3_C4_C2_2, x2 > > This is against an older verison of the code so wouldn't apply now. > It's not also checking the value of SVCR, this is checking the SME flag > passed in via x1. You can see that the SVCR value is loaded into x2 but > the check is against x1. Hi Mark, This patch aims to fix the second check (SVCR_ZA_SHIFT) instead of the first one (the x1 SME flag you're referring to): // Load ZA and ZT0 if enabled - uses x12 as scratch due to SME LDR tbz x2, #SVCR_ZA_SHIFT, 1f mov w12, #0 ldr x2, =za_in 2: _ldr_za 12, 2 If SME disabled, x2 will not have an expected value. BR, Weizhao
