Re: [PATCH] arm64/boot: Don't set PMUv3p9 FGT2 bits without PMUv3

[Bradley Morgan]

On 30 September 2026 13:12:12 BST, Fuad Tabba <fuad.tabba@xxxxxxxxx> wrote:
>On a CPU with FGT2 and an IMPLEMENTATION DEFINED PMU (PMUVer 0b1111),
>__init_el2_fgt2 sets the PMUv3p9 bits in HDFGRTR2_EL2 and HDFGWTR2_EL2,
>which are RES0 there. The macro only checks that PMUVer is at least
>PMUv3p9, and 0b1111 passes.
>
>Exclude 0b1111 before the compare, as __init_el2_debug does.
>
>Fixes: 858c7bfcb35e1 ("arm64/boot: Enable EL2 requirements for FEAT_PMUv3p9")

I see, I see.

Reviewed-by: Bradley Morgan <brads@xxxxxxxxxxxxxx>


>Signed-off-by: Fuad Tabba <fuad.tabba@xxxxxxxxx>
>---
> arch/arm64/include/asm/el2_setup.h | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
>diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
>index 87560d8b254e6..1da277baacf78 100644
>--- a/arch/arm64/include/asm/el2_setup.h
>+++ b/arch/arm64/include/asm/el2_setup.h
>@@ -421,8 +421,9 @@
> 	mov	x2, xzr
> 	mrs	x1, id_aa64dfr0_el1
> 	ubfx	x1, x1, #ID_AA64DFR0_EL1_PMUVer_SHIFT, #4
>-	cmp	x1, #ID_AA64DFR0_EL1_PMUVer_V3P9
>-	b.lt	.Lskip_pmuv3p9_\@
>+	cmp	x1, #ID_AA64DFR0_EL1_PMUVer_IMP_DEF
>+	ccmp	x1, #ID_AA64DFR0_EL1_PMUVer_V3P9, #8, ne
>+	b.lt	.Lskip_pmuv3p9_\@		// Skip if < PMUv3p9 or IMP_DEF
> 
> 	orr	x0, x0, #HDFGRTR2_EL2_nPMICNTR_EL0
> 	orr	x0, x0, #HDFGRTR2_EL2_nPMICFILTR_EL0
>
>base-commit: 72d3fcf802c45d00b300f25b848a93c3a2bd7c7e
>

--- Thanks!
"I'm not a very positive person" - Linus torvalds