* [PATCH] arm64: cpufeature: Fix GCIE field ordering in ftr_id_aa64pfr2
@ 2026-04-15 20:00 Mukesh Ojha
2026-04-16 6:42 ` Marc Zyngier
0 siblings, 1 reply; 3+ messages in thread
From: Mukesh Ojha @ 2026-04-15 20:00 UTC (permalink / raw)
To: Catalin Marinas, Will Deacon, Marc Zyngier
Cc: linux-arm-kernel, linux-kernel, Mukesh Ojha
The ftr_id_aa64pfr2[] array must be sorted in descending order of
shift value so that the overlap validation in init_cpu_features()
works correctly. The GCIE field (bits 15:12, shift=12) was placed
last in the array, after MTEFAR (bits 11:8, shift=8) and
MTESTOREONLY (bits 7:4, shift=4), causing a spurious warning at
boot:
[ 0.000000] SYS_ID_AA64PFR2_EL1 has feature overlap at shift 12
[ 0.000000] WARNING: arch/arm64/kernel/cpufeature.c:989 at init_cpu_features+0x144/0x3d0, CPU#0:
swapper/0
..
[ 0.000000] pc : init_cpu_features+0x144/0x3d0
[ 0.000000] lr : init_cpu_features+0x144/0x3d0
[ 0.000000] sp : ffffc08678f03dc0
...
0.000000] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffc08678f14000
[ 0.000000] Call trace:
[ 0.000000] init_cpu_features+0x144/0x3d0 (P)
[ 0.000000] cpuinfo_store_boot_cpu+0x4c/0x5c
[ 0.000000] smp_prepare_boot_cpu+0x28/0x38
[ 0.000000] start_kernel+0x1d4/0x848
[ 0.000000] __primary_switched+0x88/0x90
This is because the overlap check computes (shift + width) > prev_shift,
i.e. (12 + 4) > 8, which triggers since GCIE occupies bits above MTEFAR
but was listed after it.
Fix the ordering to match the register layout: FPMR(35:32), GCIE(15:12),
MTEFAR(11:8), MTESTOREONLY(7:4).
Fixes: 899ff451fcee ("KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE")
Signed-off-by: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>
---
arch/arm64/kernel/cpufeature.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 48f2d894101d..6d53bb15cf7b 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -328,9 +328,9 @@ static const struct arm64_ftr_bits ftr_id_aa64pfr1[] = {
static const struct arm64_ftr_bits ftr_id_aa64pfr2[] = {
ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR2_EL1_FPMR_SHIFT, 4, 0),
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR2_EL1_GCIE_SHIFT, 4, ID_AA64PFR2_EL1_GCIE_NI),
ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR2_EL1_MTEFAR_SHIFT, 4, ID_AA64PFR2_EL1_MTEFAR_NI),
ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR2_EL1_MTESTOREONLY_SHIFT, 4, ID_AA64PFR2_EL1_MTESTOREONLY_NI),
- ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR2_EL1_GCIE_SHIFT, 4, ID_AA64PFR2_EL1_GCIE_NI),
ARM64_FTR_END,
};
--
2.53.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] arm64: cpufeature: Fix GCIE field ordering in ftr_id_aa64pfr2
2026-04-15 20:00 [PATCH] arm64: cpufeature: Fix GCIE field ordering in ftr_id_aa64pfr2 Mukesh Ojha
@ 2026-04-16 6:42 ` Marc Zyngier
2026-04-16 12:42 ` Mukesh Ojha
0 siblings, 1 reply; 3+ messages in thread
From: Marc Zyngier @ 2026-04-16 6:42 UTC (permalink / raw)
To: Mukesh Ojha; +Cc: Catalin Marinas, Will Deacon, linux-arm-kernel, linux-kernel
On Wed, 15 Apr 2026 21:00:31 +0100,
Mukesh Ojha <mukesh.ojha@oss.qualcomm.com> wrote:
>
> The ftr_id_aa64pfr2[] array must be sorted in descending order of
> shift value so that the overlap validation in init_cpu_features()
> works correctly. The GCIE field (bits 15:12, shift=12) was placed
> last in the array, after MTEFAR (bits 11:8, shift=8) and
> MTESTOREONLY (bits 7:4, shift=4), causing a spurious warning at
> boot:
>
> [ 0.000000] SYS_ID_AA64PFR2_EL1 has feature overlap at shift 12
> [ 0.000000] WARNING: arch/arm64/kernel/cpufeature.c:989 at init_cpu_features+0x144/0x3d0, CPU#0:
> swapper/0
> ..
>
> [ 0.000000] pc : init_cpu_features+0x144/0x3d0
> [ 0.000000] lr : init_cpu_features+0x144/0x3d0
> [ 0.000000] sp : ffffc08678f03dc0
>
> ...
> 0.000000] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffc08678f14000
> [ 0.000000] Call trace:
> [ 0.000000] init_cpu_features+0x144/0x3d0 (P)
> [ 0.000000] cpuinfo_store_boot_cpu+0x4c/0x5c
> [ 0.000000] smp_prepare_boot_cpu+0x28/0x38
> [ 0.000000] start_kernel+0x1d4/0x848
> [ 0.000000] __primary_switched+0x88/0x90
>
> This is because the overlap check computes (shift + width) > prev_shift,
> i.e. (12 + 4) > 8, which triggers since GCIE occupies bits above MTEFAR
> but was listed after it.
>
> Fix the ordering to match the register layout: FPMR(35:32), GCIE(15:12),
> MTEFAR(11:8), MTESTOREONLY(7:4).
>
> Fixes: 899ff451fcee ("KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE")
> Signed-off-by: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>
This was present in next-20260403, identified the following day, a fix
proposed in [1], and the fixed commit appeared in next-20260407 (which
was the subsequent -next build) as 7e629348df81b.
May I humbly suggest that you check with the latest -next branch
before spending time on this sort of things? Two weeks is a pretty
long time...
Thanks,
M.
[1] https://lore.kernel.org/all/874ilqcu3c.wl-maz@kernel.org/
--
Without deviation from the norm, progress is not possible.
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] arm64: cpufeature: Fix GCIE field ordering in ftr_id_aa64pfr2
2026-04-16 6:42 ` Marc Zyngier
@ 2026-04-16 12:42 ` Mukesh Ojha
0 siblings, 0 replies; 3+ messages in thread
From: Mukesh Ojha @ 2026-04-16 12:42 UTC (permalink / raw)
To: Marc Zyngier; +Cc: Catalin Marinas, Will Deacon, linux-arm-kernel, linux-kernel
On Thu, Apr 16, 2026 at 07:42:14AM +0100, Marc Zyngier wrote:
> On Wed, 15 Apr 2026 21:00:31 +0100,
> Mukesh Ojha <mukesh.ojha@oss.qualcomm.com> wrote:
> >
> > The ftr_id_aa64pfr2[] array must be sorted in descending order of
> > shift value so that the overlap validation in init_cpu_features()
> > works correctly. The GCIE field (bits 15:12, shift=12) was placed
> > last in the array, after MTEFAR (bits 11:8, shift=8) and
> > MTESTOREONLY (bits 7:4, shift=4), causing a spurious warning at
> > boot:
> >
> > [ 0.000000] SYS_ID_AA64PFR2_EL1 has feature overlap at shift 12
> > [ 0.000000] WARNING: arch/arm64/kernel/cpufeature.c:989 at init_cpu_features+0x144/0x3d0, CPU#0:
> > swapper/0
> > ..
> >
> > [ 0.000000] pc : init_cpu_features+0x144/0x3d0
> > [ 0.000000] lr : init_cpu_features+0x144/0x3d0
> > [ 0.000000] sp : ffffc08678f03dc0
> >
> > ...
> > 0.000000] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffc08678f14000
> > [ 0.000000] Call trace:
> > [ 0.000000] init_cpu_features+0x144/0x3d0 (P)
> > [ 0.000000] cpuinfo_store_boot_cpu+0x4c/0x5c
> > [ 0.000000] smp_prepare_boot_cpu+0x28/0x38
> > [ 0.000000] start_kernel+0x1d4/0x848
> > [ 0.000000] __primary_switched+0x88/0x90
> >
> > This is because the overlap check computes (shift + width) > prev_shift,
> > i.e. (12 + 4) > 8, which triggers since GCIE occupies bits above MTEFAR
> > but was listed after it.
> >
> > Fix the ordering to match the register layout: FPMR(35:32), GCIE(15:12),
> > MTEFAR(11:8), MTESTOREONLY(7:4).
> >
> > Fixes: 899ff451fcee ("KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE")
> > Signed-off-by: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>
>
> This was present in next-20260403, identified the following day, a fix
> proposed in [1], and the fixed commit appeared in next-20260407 (which
> was the subsequent -next build) as 7e629348df81b.
>
> May I humbly suggest that you check with the latest -next branch
> before spending time on this sort of things? Two weeks is a pretty
> long time...
Sure, Thank you.
>
> Thanks,
>
> M.
>
> [1] https://lore.kernel.org/all/874ilqcu3c.wl-maz@kernel.org/
>
> --
> Without deviation from the norm, progress is not possible.
--
-Mukesh Ojha
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2026-04-16 12:42 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-04-15 20:00 [PATCH] arm64: cpufeature: Fix GCIE field ordering in ftr_id_aa64pfr2 Mukesh Ojha
2026-04-16 6:42 ` Marc Zyngier
2026-04-16 12:42 ` Mukesh Ojha
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox