* Re: [PATCH] arm64/sysreg: Fix BWE field encoding in ID_AA64DFR2_EL1
2026-06-30 22:23 [PATCH] arm64/sysreg: Fix BWE field encoding in ID_AA64DFR2_EL1 Jia He
@ 2026-07-01 14:29 ` Marc Zyngier
2026-07-01 17:09 ` Oliver Upton
2026-07-02 12:58 ` Will Deacon
2 siblings, 0 replies; 4+ messages in thread
From: Marc Zyngier @ 2026-07-01 14:29 UTC (permalink / raw)
To: Jia He
Cc: Catalin Marinas, Will Deacon, linux-arm-kernel, Lorenzo Pieralisi,
Mark Brown, Sascha Bischoff, Fuad Tabba, Anshuman Khandual,
Oliver Upton, linux-kernel, Bin Guo
On Tue, 30 Jun 2026 23:23:47 +0100,
Jia He <justin.he@arm.com> wrote:
>
> Commit 93d7356e4b30 ("arm64: sysreg: Describe ID_AA64DFR2_EL1 fields")
> encodes the FEAT_BWE2 value of the BWE field as '0b0002'. Binary
> literals only accept the digits 0 and 1, so the intended value is 2,
> i.e. 0b0010.
>
> The macro generated by gen-sysreg.awk currently expands to
> #define ID_AA64DFR2_EL1_BWE_FEAT_BWE2 UL(0b0002)
> is not legal C and would fail to compile if any in-tree code referenced
> it. At present no caller uses this enum value, so the kernel still
> builds cleanly, but the bug is latent.
>
> Fix the typo by using the correct binary literal 0b0010.
>
> Cc: Bin Guo <guobin@linux.alibaba.com>
> Fixes: 93d7356e4b30 ("arm64: sysreg: Describe ID_AA64DFR2_EL1 fields")
> Signed-off-by: Jia He <justin.he@arm.com>
> Reviewed-by: Mark Brown <broonie@kernel.org>
> ---
> arch/arm64/tools/sysreg | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg
> index bc1788b1662b..7cb61aca3797 100644
> --- a/arch/arm64/tools/sysreg
> +++ b/arch/arm64/tools/sysreg
> @@ -1806,7 +1806,7 @@ Res0 15:8
> UnsignedEnum 7:4 BWE
> 0b0000 NI
> 0b0001 FEAT_BWE
> - 0b0002 FEAT_BWE2
> + 0b0010 FEAT_BWE2
Well, that was embarrassing. FWIW (and given the original patch,
that's not much):
Acked-by: Marc Zyngier <maz@kernel.org>
M.
--
Without deviation from the norm, progress is not possible.
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] arm64/sysreg: Fix BWE field encoding in ID_AA64DFR2_EL1
2026-06-30 22:23 [PATCH] arm64/sysreg: Fix BWE field encoding in ID_AA64DFR2_EL1 Jia He
2026-07-01 14:29 ` Marc Zyngier
@ 2026-07-01 17:09 ` Oliver Upton
2026-07-02 12:58 ` Will Deacon
2 siblings, 0 replies; 4+ messages in thread
From: Oliver Upton @ 2026-07-01 17:09 UTC (permalink / raw)
To: Jia He
Cc: Catalin Marinas, Will Deacon, Marc Zyngier, linux-arm-kernel,
Lorenzo Pieralisi, Mark Brown, Sascha Bischoff, Fuad Tabba,
Anshuman Khandual, linux-kernel, Bin Guo
On Tue, Jun 30, 2026 at 10:23:47PM +0000, Jia He wrote:
> Commit 93d7356e4b30 ("arm64: sysreg: Describe ID_AA64DFR2_EL1 fields")
> encodes the FEAT_BWE2 value of the BWE field as '0b0002'. Binary
> literals only accept the digits 0 and 1, so the intended value is 2,
> i.e. 0b0010.
>
> The macro generated by gen-sysreg.awk currently expands to
> #define ID_AA64DFR2_EL1_BWE_FEAT_BWE2 UL(0b0002)
> is not legal C and would fail to compile if any in-tree code referenced
> it. At present no caller uses this enum value, so the kernel still
> builds cleanly, but the bug is latent.
>
> Fix the typo by using the correct binary literal 0b0010.
>
> Cc: Bin Guo <guobin@linux.alibaba.com>
> Fixes: 93d7356e4b30 ("arm64: sysreg: Describe ID_AA64DFR2_EL1 fields")
> Signed-off-by: Jia He <justin.he@arm.com>
> Reviewed-by: Mark Brown <broonie@kernel.org>
Hah, I screwed that up pretty good!
Reviewed-by: Oliver Upton <oupton@kernel.org>
> ---
> arch/arm64/tools/sysreg | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg
> index bc1788b1662b..7cb61aca3797 100644
> --- a/arch/arm64/tools/sysreg
> +++ b/arch/arm64/tools/sysreg
> @@ -1806,7 +1806,7 @@ Res0 15:8
> UnsignedEnum 7:4 BWE
> 0b0000 NI
> 0b0001 FEAT_BWE
> - 0b0002 FEAT_BWE2
> + 0b0010 FEAT_BWE2
> EndEnum
> UnsignedEnum 3:0 STEP
> 0b0000 NI
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] arm64/sysreg: Fix BWE field encoding in ID_AA64DFR2_EL1
2026-06-30 22:23 [PATCH] arm64/sysreg: Fix BWE field encoding in ID_AA64DFR2_EL1 Jia He
2026-07-01 14:29 ` Marc Zyngier
2026-07-01 17:09 ` Oliver Upton
@ 2026-07-02 12:58 ` Will Deacon
2 siblings, 0 replies; 4+ messages in thread
From: Will Deacon @ 2026-07-02 12:58 UTC (permalink / raw)
To: Catalin Marinas, Marc Zyngier, linux-arm-kernel, Jia He
Cc: kernel-team, Will Deacon, Lorenzo Pieralisi, Mark Brown,
Sascha Bischoff, Fuad Tabba, Anshuman Khandual, Oliver Upton,
linux-kernel, Bin Guo
On Tue, 30 Jun 2026 22:23:47 +0000, Jia He wrote:
> Commit 93d7356e4b30 ("arm64: sysreg: Describe ID_AA64DFR2_EL1 fields")
> encodes the FEAT_BWE2 value of the BWE field as '0b0002'. Binary
> literals only accept the digits 0 and 1, so the intended value is 2,
> i.e. 0b0010.
>
> The macro generated by gen-sysreg.awk currently expands to
> #define ID_AA64DFR2_EL1_BWE_FEAT_BWE2 UL(0b0002)
> is not legal C and would fail to compile if any in-tree code referenced
> it. At present no caller uses this enum value, so the kernel still
> builds cleanly, but the bug is latent.
>
> [...]
Applied to arm64 (for-next/fixes), thanks!
[1/1] arm64/sysreg: Fix BWE field encoding in ID_AA64DFR2_EL1
https://git.kernel.org/arm64/c/6666336d8fe5
Cheers,
--
Will
https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev
^ permalink raw reply [flat|nested] 4+ messages in thread