* [PATCH] KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE
@ 2026-04-01 17:00 Marc Zyngier
2026-04-01 17:09 ` Catalin Marinas
` (2 more replies)
0 siblings, 3 replies; 7+ messages in thread
From: Marc Zyngier @ 2026-04-01 17:00 UTC (permalink / raw)
To: kvmarm, linux-arm-kernel
Cc: Joey Gouly, Suzuki K Poulose, Oliver Upton, Zenghui Yu,
Sascha Bischoff, Will Deacon, Catalin Marinas
As we are missing ID_AA64PFR2_EL1.GCIE from the kernel feature set,
userspace cannot write ID_AA64PFR2_EL1 with GCIE set, even if we are
on a GICv5 host.
Add the required field description.
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kernel/cpufeature.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 32c2dbcc0c641..5bca6e064ca72 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -327,6 +327,7 @@ 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_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,
};
--
2.47.3
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH] KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE
2026-04-01 17:00 [PATCH] KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE Marc Zyngier
@ 2026-04-01 17:09 ` Catalin Marinas
2026-04-02 13:37 ` Marc Zyngier
2026-04-04 18:13 ` Nathan Chancellor
2 siblings, 0 replies; 7+ messages in thread
From: Catalin Marinas @ 2026-04-01 17:09 UTC (permalink / raw)
To: Marc Zyngier
Cc: kvmarm, linux-arm-kernel, Joey Gouly, Suzuki K Poulose,
Oliver Upton, Zenghui Yu, Sascha Bischoff, Will Deacon
On Wed, Apr 01, 2026 at 06:00:17PM +0100, Marc Zyngier wrote:
> As we are missing ID_AA64PFR2_EL1.GCIE from the kernel feature set,
> userspace cannot write ID_AA64PFR2_EL1 with GCIE set, even if we are
> on a GICv5 host.
>
> Add the required field description.
>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE
2026-04-01 17:00 [PATCH] KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE Marc Zyngier
2026-04-01 17:09 ` Catalin Marinas
@ 2026-04-02 13:37 ` Marc Zyngier
2026-04-04 18:13 ` Nathan Chancellor
2 siblings, 0 replies; 7+ messages in thread
From: Marc Zyngier @ 2026-04-02 13:37 UTC (permalink / raw)
To: kvmarm, linux-arm-kernel, Marc Zyngier
Cc: Joey Gouly, Suzuki K Poulose, Oliver Upton, Zenghui Yu,
Sascha Bischoff, Will Deacon, Catalin Marinas
On Wed, 01 Apr 2026 18:00:17 +0100, Marc Zyngier wrote:
> As we are missing ID_AA64PFR2_EL1.GCIE from the kernel feature set,
> userspace cannot write ID_AA64PFR2_EL1 with GCIE set, even if we are
> on a GICv5 host.
>
> Add the required field description.
>
>
> [...]
Applied to next, thanks!
[1/1] KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE
commit: 899ff451fcee1289f3f37d061da66c3e38748a69
Cheers,
M.
--
Without deviation from the norm, progress is not possible.
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH] KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE
2026-04-01 17:00 [PATCH] KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE Marc Zyngier
2026-04-01 17:09 ` Catalin Marinas
2026-04-02 13:37 ` Marc Zyngier
@ 2026-04-04 18:13 ` Nathan Chancellor
2026-04-04 21:07 ` Marc Zyngier
2 siblings, 1 reply; 7+ messages in thread
From: Nathan Chancellor @ 2026-04-04 18:13 UTC (permalink / raw)
To: Marc Zyngier
Cc: kvmarm, linux-arm-kernel, Joey Gouly, Suzuki K Poulose,
Oliver Upton, Zenghui Yu, Sascha Bischoff, Will Deacon,
Catalin Marinas
Hi Marc,
On Wed, Apr 01, 2026 at 06:00:17PM +0100, Marc Zyngier wrote:
> As we are missing ID_AA64PFR2_EL1.GCIE from the kernel feature set,
> userspace cannot write ID_AA64PFR2_EL1 with GCIE set, even if we are
> on a GICv5 host.
>
> Add the required field description.
>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
> arch/arm64/kernel/cpufeature.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 32c2dbcc0c641..5bca6e064ca72 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -327,6 +327,7 @@ 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_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,
> };
>
> --
> 2.47.3
>
After this change in -next as commit 899ff451fcee ("KVM: arm64:
Advertise ID_AA64PFR2_EL1.GCIE"), I am seeing a warning on boot in my
simple QEMU boot tests.
$ make -skj"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux- mrproper virtconfig Image.gz
$ curl -LSs https://github.com/ClangBuiltLinux/boot-utils/releases/download/20241120-044434/arm64-rootfs.cpio.zst | zstd -d >rootfs.cpio
$ qemu-system-aarch64 \
-display none \
-nodefaults \
-machine virt,gic-version=max \
-append 'console=ttyAMA0 earlycon' \
-kernel arch/arm64/boot/Image.gz \
-initrd rootfs.cpio \
-cpu host \
-enable-kvm \
-m 1G \
-smp 8 \
-serial mon:stdio
[ 0.000000] Booting Linux on physical CPU 0x0000000000 [0x413fd0c1]
[ 0.000000] Linux version 7.0.0-rc4-00058-g899ff451fcee (nathan@aadp) (aarch64-linux-gcc (GCC) 15.2.0, GNU ld (GNU Binutils) 2.45) #1 SMP PREEMPT Sat Apr 4 06:55:05 MST 2026
...
[ 0.000000] ------------[ cut here ]------------
[ 0.000000] SYS_ID_AA64PFR2_EL1 has feature overlap at shift 12
[ 0.000000] WARNING: arch/arm64/kernel/cpufeature.c:986 at init_cpu_features+0xbc/0x344, CPU#0: swapper/0
[ 0.000000] Modules linked in:
[ 0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 7.0.0-rc4-00058-g899ff451fcee #1 PREEMPT
[ 0.000000] Hardware name: linux,dummy-virt (DT)
[ 0.000000] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 0.000000] pc : init_cpu_features+0xbc/0x344
[ 0.000000] lr : init_cpu_features+0xbc/0x344
[ 0.000000] sp : ffffcd0982373db0
[ 0.000000] x29: ffffcd0982373db0 x28: 0000000000000010 x27: ffffcd0981c63878
[ 0.000000] x26: 0000000000000018 x25: ffffcd0982013f38 x24: ffffcd0981c69068
[ 0.000000] x23: ffffcd0981c635f0 x22: ffffcd0982388640 x21: 0000000000000003
[ 0.000000] x20: 0000000000000017 x19: ffffcd09824c9308 x18: 000000000000000a
[ 0.000000] x17: 5d305b203837205d x16: 305b203737205d30 x15: 0000000000000000
[ 0.000000] x14: 0000000000000000 x13: 3231207466696873 x12: 2074612070616c72
[ 0.000000] x11: 0000000000000058 x10: 0000000000000018 x9 : ffffcd0982396598
[ 0.000000] x8 : 0000000000057fa8 x7 : 000000000000002a x6 : ffffcd09823ee598
[ 0.000000] x5 : ffffcd09823ee598 x4 : 0000000000000000 x3 : 0000000000000000
[ 0.000000] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffcd09823852c0
[ 0.000000] Call trace:
[ 0.000000] init_cpu_features+0xbc/0x344 (P)
[ 0.000000] cpuinfo_store_boot_cpu+0x48/0x54
[ 0.000000] smp_prepare_boot_cpu+0x28/0x38
[ 0.000000] start_kernel+0x248/0x780
[ 0.000000] __primary_switched+0x88/0x90
[ 0.000000] ---[ end trace 0000000000000000 ]---
...
```
Is this expected? I assume not, hence the report. If there is any
information I can provide or patches I can test, I am more than happy to
do so.
Cheers,
Nathan
# bad: [2febe6e6ee6e34c7754eff3c4d81aa7b0dcb7979] Add linux-next specific files for 20260403
# good: [d8a9a4b11a137909e306e50346148fc5c3b63f9d] Merge tag 'v7.0-rc6-smb3-client-fix' of git://git.samba.org/sfrench/cifs-2.6
git bisect start 'origin/master' 'origin/stable'
# bad: [dc9c72702de7e46679f8c2ab2175ab7070baa3ee] Merge branch 'main' of https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
git bisect bad dc9c72702de7e46679f8c2ab2175ab7070baa3ee
# bad: [d5ea83fae6558b2431b022781f6ccb74d241b2bb] Merge branch 'for-next' of https://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git
git bisect bad d5ea83fae6558b2431b022781f6ccb74d241b2bb
# bad: [d16ebd2d0dc90f1561d0a44a828db2c9148ad5f4] Merge branch 'for-next/perf' of https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git
git bisect bad d16ebd2d0dc90f1561d0a44a828db2c9148ad5f4
# bad: [768784742008ccebbf3e88a26a6e9e6aad76dc8e] Merge branch 'timekeeping-next' of https://github.com/Rust-for-Linux/linux.git
git bisect bad 768784742008ccebbf3e88a26a6e9e6aad76dc8e
# good: [b671065be2bef906bb3e0c1bc7be4055e84ea1d3] Merge branch 'at91-fixes' of https://git.kernel.org/pub/scm/linux/kernel/git/at91/linux.git
git bisect good b671065be2bef906bb3e0c1bc7be4055e84ea1d3
# bad: [bd1f7328e25426f08cafa8333293411788c7957b] Merge branch kvm-arm64/vgic-fixes-7.1 into kvmarm-master/next
git bisect bad bd1f7328e25426f08cafa8333293411788c7957b
# good: [1cd0bb0425594cea9baf862393a4ca9cc0c018a3] Merge branch kvm-arm64/pkvm-psci into kvmarm-master/next
git bisect good 1cd0bb0425594cea9baf862393a4ca9cc0c018a3
# good: [bc20692f528b2ac8226bafe5b1db9a1f8be96dbf] KVM: arm64: Don't hold 'vm_table_lock' across guest page reclaim
git bisect good bc20692f528b2ac8226bafe5b1db9a1f8be96dbf
# good: [adb70b3a8b31e9eb05f2ec3c76d85f9a7a8c8cbc] KVM: arm64: Directly expose mapping prot and kill kvm_s2_fault
git bisect good adb70b3a8b31e9eb05f2ec3c76d85f9a7a8c8cbc
# good: [be46a408f376df31762e8a9914dc6d082755e686] KVM: arm64: Correctly plumb ID_AA64PFR2_EL1 into pkvm idreg handling
git bisect good be46a408f376df31762e8a9914dc6d082755e686
# good: [33cdd7f8fa32c92317aa521bd6f407a3cba8474b] Merge branch kvm-arm64/spe-trbe-nvhe into kvmarm-master/next
git bisect good 33cdd7f8fa32c92317aa521bd6f407a3cba8474b
# good: [e54971a0468a8bc82b1976d5b010392d7cb689b9] Merge branch kvm-arm64/vgic-fixes-7.1 into kvmarm-master/next
git bisect good e54971a0468a8bc82b1976d5b010392d7cb689b9
# bad: [899ff451fcee1289f3f37d061da66c3e38748a69] KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE
git bisect bad 899ff451fcee1289f3f37d061da66c3e38748a69
# good: [9c1ac77ddfc90b6292ef63a4fa5ab6f9e4b29981] KVM: arm64: vgic-v5: Fold PPI state for all exposed PPIs
git bisect good 9c1ac77ddfc90b6292ef63a4fa5ab6f9e4b29981
# first bad commit: [899ff451fcee1289f3f37d061da66c3e38748a69] KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH] KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE
2026-04-04 18:13 ` Nathan Chancellor
@ 2026-04-04 21:07 ` Marc Zyngier
2026-04-06 7:32 ` Nathan Chancellor
0 siblings, 1 reply; 7+ messages in thread
From: Marc Zyngier @ 2026-04-04 21:07 UTC (permalink / raw)
To: Nathan Chancellor
Cc: kvmarm, linux-arm-kernel, Joey Gouly, Suzuki K Poulose,
Oliver Upton, Zenghui Yu, Sascha Bischoff, Will Deacon,
Catalin Marinas
On Sat, 04 Apr 2026 19:13:30 +0100,
Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi Marc,
>
> On Wed, Apr 01, 2026 at 06:00:17PM +0100, Marc Zyngier wrote:
> > As we are missing ID_AA64PFR2_EL1.GCIE from the kernel feature set,
> > userspace cannot write ID_AA64PFR2_EL1 with GCIE set, even if we are
> > on a GICv5 host.
> >
> > Add the required field description.
> >
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > ---
> > arch/arm64/kernel/cpufeature.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> > index 32c2dbcc0c641..5bca6e064ca72 100644
> > --- a/arch/arm64/kernel/cpufeature.c
> > +++ b/arch/arm64/kernel/cpufeature.c
> > @@ -327,6 +327,7 @@ 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_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,
> > };
> >
> > --
> > 2.47.3
> >
>
> After this change in -next as commit 899ff451fcee ("KVM: arm64:
> Advertise ID_AA64PFR2_EL1.GCIE"), I am seeing a warning on boot in my
> simple QEMU boot tests.
>
> $ make -skj"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux- mrproper virtconfig Image.gz
>
> $ curl -LSs https://github.com/ClangBuiltLinux/boot-utils/releases/download/20241120-044434/arm64-rootfs.cpio.zst | zstd -d >rootfs.cpio
>
> $ qemu-system-aarch64 \
> -display none \
> -nodefaults \
> -machine virt,gic-version=max \
> -append 'console=ttyAMA0 earlycon' \
> -kernel arch/arm64/boot/Image.gz \
> -initrd rootfs.cpio \
> -cpu host \
> -enable-kvm \
> -m 1G \
> -smp 8 \
> -serial mon:stdio
> [ 0.000000] Booting Linux on physical CPU 0x0000000000 [0x413fd0c1]
> [ 0.000000] Linux version 7.0.0-rc4-00058-g899ff451fcee (nathan@aadp) (aarch64-linux-gcc (GCC) 15.2.0, GNU ld (GNU Binutils) 2.45) #1 SMP PREEMPT Sat Apr 4 06:55:05 MST 2026
> ...
> [ 0.000000] ------------[ cut here ]------------
> [ 0.000000] SYS_ID_AA64PFR2_EL1 has feature overlap at shift 12
> [ 0.000000] WARNING: arch/arm64/kernel/cpufeature.c:986 at init_cpu_features+0xbc/0x344, CPU#0: swapper/0
> [ 0.000000] Modules linked in:
> [ 0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 7.0.0-rc4-00058-g899ff451fcee #1 PREEMPT
> [ 0.000000] Hardware name: linux,dummy-virt (DT)
> [ 0.000000] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [ 0.000000] pc : init_cpu_features+0xbc/0x344
> [ 0.000000] lr : init_cpu_features+0xbc/0x344
> [ 0.000000] sp : ffffcd0982373db0
> [ 0.000000] x29: ffffcd0982373db0 x28: 0000000000000010 x27: ffffcd0981c63878
> [ 0.000000] x26: 0000000000000018 x25: ffffcd0982013f38 x24: ffffcd0981c69068
> [ 0.000000] x23: ffffcd0981c635f0 x22: ffffcd0982388640 x21: 0000000000000003
> [ 0.000000] x20: 0000000000000017 x19: ffffcd09824c9308 x18: 000000000000000a
> [ 0.000000] x17: 5d305b203837205d x16: 305b203737205d30 x15: 0000000000000000
> [ 0.000000] x14: 0000000000000000 x13: 3231207466696873 x12: 2074612070616c72
> [ 0.000000] x11: 0000000000000058 x10: 0000000000000018 x9 : ffffcd0982396598
> [ 0.000000] x8 : 0000000000057fa8 x7 : 000000000000002a x6 : ffffcd09823ee598
> [ 0.000000] x5 : ffffcd09823ee598 x4 : 0000000000000000 x3 : 0000000000000000
> [ 0.000000] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffcd09823852c0
> [ 0.000000] Call trace:
> [ 0.000000] init_cpu_features+0xbc/0x344 (P)
> [ 0.000000] cpuinfo_store_boot_cpu+0x48/0x54
> [ 0.000000] smp_prepare_boot_cpu+0x28/0x38
> [ 0.000000] start_kernel+0x248/0x780
> [ 0.000000] __primary_switched+0x88/0x90
> [ 0.000000] ---[ end trace 0000000000000000 ]---
> ...
> ```
>
> Is this expected? I assume not, hence the report. If there is any
> information I can provide or patches I can test, I am more than happy to
> do so.
Gah. No idea how I managed to miss that: the register fields must be
strictly ordered, and I placed the field in the wrong spot. The
following hack fixes it for me:
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 5bca6e064ca72..1bfaa96881dab 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -325,9 +325,9 @@ 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,
};
If that works for you, I'll fold that into the original patch...
Thanks for pointing this out!
M.
--
Jazz isn't dead. It just smells funny.
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH] KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE
2026-04-04 21:07 ` Marc Zyngier
@ 2026-04-06 7:32 ` Nathan Chancellor
0 siblings, 0 replies; 7+ messages in thread
From: Nathan Chancellor @ 2026-04-06 7:32 UTC (permalink / raw)
To: Marc Zyngier
Cc: kvmarm, linux-arm-kernel, Joey Gouly, Suzuki K Poulose,
Oliver Upton, Zenghui Yu, Sascha Bischoff, Will Deacon,
Catalin Marinas
On Sat, Apr 04, 2026 at 10:07:51PM +0100, Marc Zyngier wrote:
> Gah. No idea how I managed to miss that: the register fields must be
> strictly ordered, and I placed the field in the wrong spot. The
> following hack fixes it for me:
>
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 5bca6e064ca72..1bfaa96881dab 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -325,9 +325,9 @@ 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,
> };
>
> If that works for you, I'll fold that into the original patch...
Can confirm.
> Thanks for pointing this out!
Thanks for the quick fix!
Cheers,
Nathan
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE
@ 2026-04-05 12:08 Biju Das
0 siblings, 0 replies; 7+ messages in thread
From: Biju Das @ 2026-04-05 12:08 UTC (permalink / raw)
To: maz@kernel.org
Cc: catalin.marinas@arm.com, joey.gouly@arm.com,
kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
nathan@kernel.org, oupton@kernel.org, sascha.bischoff@arm.com,
suzuki.poulose@arm.com, will@kernel.org, yuzenghui@huawei.com
Hi,
> Hi Marc,
>
> On Wed, Apr 01, 2026 at 06:00:17PM +0100, Marc Zyngier wrote:
> > As we are missing ID_AA64PFR2_EL1.GCIE from the kernel feature set,
> > userspace cannot write ID_AA64PFR2_EL1 with GCIE set, even if we are
> > on a GICv5 host.
> >
> > Add the required field description.
> >
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > ---
> > arch/arm64/kernel/cpufeature.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> > index 32c2dbcc0c641..5bca6e064ca72 100644
> > --- a/arch/arm64/kernel/cpufeature.c
> > +++ b/arch/arm64/kernel/cpufeature.c
> > @@ -327,6 +327,7 @@ 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_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,
> > };
> >
> > --
> > 2.47.3
> >
>
> After this change in -next as commit 899ff451fcee ("KVM: arm64:
> Advertise ID_AA64PFR2_EL1.GCIE"), I am seeing a warning on boot in my
> simple QEMU boot tests.
>
> $ make -skj"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux- mrproper virtconfig Image.gz
>
> $ curl -LSs https://github.com/ClangBuiltLinux/boot-utils/releases/download/20241120-044434/arm64-rootfs.cpio.zst | zstd -d >rootfs.cpio
>
> $ qemu-system-aarch64 \
> -display none \
> -nodefaults \
> -machine virt,gic-version=max \
> -append 'console=ttyAMA0 earlycon' \
> -kernel arch/arm64/boot/Image.gz \
> -initrd rootfs.cpio \
> -cpu host \
> -enable-kvm \
> -m 1G \
> -smp 8 \
> -serial mon:stdio
> [ 0.000000] Booting Linux on physical CPU 0x0000000000 [0x413fd0c1]
> [ 0.000000] Linux version 7.0.0-rc4-00058-g899ff451fcee (nathan@aadp) (aarch64-linux-gcc (GCC) 15.2.0, GNU ld (GNU Binutils) 2.45) #1 SMP PREEMPT Sat Apr 4 06:55:05 MST 2026
> ...
> [ 0.000000] ------------[ cut here ]------------
> [ 0.000000] SYS_ID_AA64PFR2_EL1 has feature overlap at shift 12
> [ 0.000000] WARNING: arch/arm64/kernel/cpufeature.c:986 at init_cpu_features+0xbc/0x344, CPU#0: swapper/0
> [ 0.000000] Modules linked in:
> [ 0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 7.0.0-rc4-00058-g899ff451fcee #1 PREEMPT
> [ 0.000000] Hardware name: linux,dummy-virt (DT)
> [ 0.000000] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [ 0.000000] pc : init_cpu_features+0xbc/0x344
> [ 0.000000] lr : init_cpu_features+0xbc/0x344
> [ 0.000000] sp : ffffcd0982373db0
> [ 0.000000] x29: ffffcd0982373db0 x28: 0000000000000010 x27: ffffcd0981c63878
> [ 0.000000] x26: 0000000000000018 x25: ffffcd0982013f38 x24: ffffcd0981c69068
> [ 0.000000] x23: ffffcd0981c635f0 x22: ffffcd0982388640 x21: 0000000000000003
> [ 0.000000] x20: 0000000000000017 x19: ffffcd09824c9308 x18: 000000000000000a
> [ 0.000000] x17: 5d305b203837205d x16: 305b203737205d30 x15: 0000000000000000
> [ 0.000000] x14: 0000000000000000 x13: 3231207466696873 x12: 2074612070616c72
> [ 0.000000] x11: 0000000000000058 x10: 0000000000000018 x9 : ffffcd0982396598
> [ 0.000000] x8 : 0000000000057fa8 x7 : 000000000000002a x6 : ffffcd09823ee598
> [ 0.000000] x5 : ffffcd09823ee598 x4 : 0000000000000000 x3 : 0000000000000000
> [ 0.000000] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffcd09823852c0
> [ 0.000000] Call trace:
> [ 0.000000] init_cpu_features+0xbc/0x344 (P)
> [ 0.000000] cpuinfo_store_boot_cpu+0x48/0x54
> [ 0.000000] smp_prepare_boot_cpu+0x28/0x38
> [ 0.000000] start_kernel+0x248/0x780
> [ 0.000000] __primary_switched+0x88/0x90
> [ 0.000000] ---[ end trace 0000000000000000 ]---
> ...
> ```
>
> Is this expected? I assume not, hence the report. If there is any
> information I can provide or patches I can test, I am more than happy to
> do so.
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 5bca6e064ca72..1bfaa96881dab 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -325,9 +325,9 @@ 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,
};
The below next-20260403 warning on RZ/G3L SMARC EVK is fixed by the above code.
[ 0.000000] Call trace:
[ 0.000000] init_cpu_features+0xb8/0x2fc (P)
[ 0.000000] cpuinfo_store_boot_cpu+0x48/0x54
[ 0.000000] smp_prepare_boot_cpu+0x24/0x30
[ 0.000000] start_kernel+0x230/0x6a4
[ 0.000000] __primary_switched+0x88/0x90
Cheers,
Biju
^ permalink raw reply related [flat|nested] 7+ messages in thread
end of thread, other threads:[~2026-04-06 7:32 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
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2026-04-01 17:00 [PATCH] KVM: arm64: Advertise ID_AA64PFR2_EL1.GCIE Marc Zyngier
2026-04-01 17:09 ` Catalin Marinas
2026-04-02 13:37 ` Marc Zyngier
2026-04-04 18:13 ` Nathan Chancellor
2026-04-04 21:07 ` Marc Zyngier
2026-04-06 7:32 ` Nathan Chancellor
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2026-04-05 12:08 Biju Das
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