* [PATCH] arm64/boot: Don't set PMUv3p9 FGT2 bits without PMUv3
@ 2026-09-30 12:12 Fuad Tabba
2026-09-30 13:26 ` Anshuman Khandual
2026-10-01 2:59 ` Anshuman Khandual
0 siblings, 2 replies; 4+ messages in thread
From: Fuad Tabba @ 2026-09-30 12:12 UTC (permalink / raw)
To: Catalin Marinas, Will Deacon
Cc: Mark Rutland, Marc Zyngier, Oliver Upton, Anshuman Khandual,
Rob Herring (Arm),
Fuad Tabba, linux-arm-kernel, linux-kernel
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")
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---
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
--
2.39.5
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64/boot: Don't set PMUv3p9 FGT2 bits without PMUv3
2026-09-30 12:12 [PATCH] arm64/boot: Don't set PMUv3p9 FGT2 bits without PMUv3 Fuad Tabba
@ 2026-09-30 13:26 ` Anshuman Khandual
2026-09-30 13:32 ` Fuad Tabba
2026-10-01 2:59 ` Anshuman Khandual
1 sibling, 1 reply; 4+ messages in thread
From: Anshuman Khandual @ 2026-09-30 13:26 UTC (permalink / raw)
To: Fuad Tabba
Cc: Catalin Marinas, Will Deacon, Mark Rutland, Marc Zyngier,
Oliver Upton, Rob Herring (Arm),
Fuad Tabba, linux-arm-kernel, linux-kernel
On Wed, Sep 30, 2026 at 01:12:12PM +0100, Fuad Tabba 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.
Just curious - has this caused any real world problem on IMP defined PMUs ?
>
> Exclude 0b1111 before the compare, as __init_el2_debug does.
>
> Fixes: 858c7bfcb35e1 ("arm64/boot: Enable EL2 requirements for FEAT_PMUv3p9")
> Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
> ---
> 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
> --
> 2.39.5
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64/boot: Don't set PMUv3p9 FGT2 bits without PMUv3
2026-09-30 13:26 ` Anshuman Khandual
@ 2026-09-30 13:32 ` Fuad Tabba
0 siblings, 0 replies; 4+ messages in thread
From: Fuad Tabba @ 2026-09-30 13:32 UTC (permalink / raw)
To: Anshuman Khandual
Cc: Catalin Marinas, Will Deacon, Mark Rutland, Marc Zyngier,
Oliver Upton, Rob Herring (Arm),
linux-arm-kernel, linux-kernel
Hi Anshuman,
On Wed, 30 Sept 2026 at 14:26, Anshuman Khandual
<anshuman.khandual@arm.com> wrote:
>
> On Wed, Sep 30, 2026 at 01:12:12PM +0100, Fuad Tabba 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.
>
> Just curious - has this caused any real world problem on IMP defined PMUs ?
Not as far as I know. I found it while auditing these and related bits for pKVM.
Cheers,
/fuad
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64/boot: Don't set PMUv3p9 FGT2 bits without PMUv3
2026-09-30 12:12 [PATCH] arm64/boot: Don't set PMUv3p9 FGT2 bits without PMUv3 Fuad Tabba
2026-09-30 13:26 ` Anshuman Khandual
@ 2026-10-01 2:59 ` Anshuman Khandual
1 sibling, 0 replies; 4+ messages in thread
From: Anshuman Khandual @ 2026-10-01 2:59 UTC (permalink / raw)
To: Fuad Tabba
Cc: Catalin Marinas, Will Deacon, Mark Rutland, Marc Zyngier,
Oliver Upton, Rob Herring (Arm),
Fuad Tabba, linux-arm-kernel, linux-kernel
On Wed, Sep 30, 2026 at 01:12:12PM +0100, Fuad Tabba 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")
> Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
This fixes a semantics error during feature detection while also preventing
undesirable writes into RES0 fields in IMPLEMENTATION DEFINED PMU instances.
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> 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
> --
> 2.39.5
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2026-09-30 12:12 [PATCH] arm64/boot: Don't set PMUv3p9 FGT2 bits without PMUv3 Fuad Tabba
2026-09-30 13:26 ` Anshuman Khandual
2026-09-30 13:32 ` Fuad Tabba
2026-10-01 2:59 ` Anshuman Khandual
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