diff options
| author | Amit Machhiwal <amachhiw@linux.ibm.com> | 2026-06-14 23:04:37 +0530 |
|---|---|---|
| committer | Madhavan Srinivasan <maddy@linux.ibm.com> | 2026-07-15 08:04:13 +0530 |
| commit | e4de1b9cb3b5c981e4fe9bca253a7fb9161f5acd (patch) | |
| tree | 4d4a54feab60dc7388bad0fe20061e8a4258c8fe /arch | |
| parent | bd83c98b988d2c560531084e296dbfb530aff829 (diff) | |
powerpc/dt_cpu_ftrs: Set CPU_FTR_P11_PVR for Power11 and later processors
When using device tree CPU features (dt-cpu-ftrs), the kernel bypasses
the traditional cputable-based CPU identification and instead derives
CPU features from the device tree's "ibm,powerpc-cpu-features" node
provided by firmware.
However, CPU_FTR_P11_PVR is a kernel-internal feature flag used to
identify Power11 and later processors, and is not represented in the
device tree's ISA feature set. While ISA v3.1 support (indicated by
CPU_FTR_ARCH_31) is present on both Power10 and Power11, the
CPU_FTR_P11_PVR flag is specifically needed by code that must
distinguish between Power10 and Power11 processors.
Without this flag set, code that checks for Power11 using
cpu_has_feature(CPU_FTR_P11_PVR) will incorrectly return false on
Power11+ systems using dt-cpu-ftrs, leading to incorrect behavior.
This issue manifests specifically in powernv environments (bare-metal
or QEMU TCG with powernv machine type), where skiboot/OPAL firmware
provides the "ibm,powerpc-cpu-features" node, causing the kernel to
use dt-cpu-ftrs. The issue does not affect pseries guests, where SLOF
firmware does not provide this node, causing the kernel to fall back
to the traditional cputable path (identify_cpu) which correctly sets
CPU_FTR_P11_PVR during PVR-based CPU identification.
In powernv TCG guests, the missing flag causes KVM code to trigger
warnings when attempting to create KVM guests, as cpu_features shows
0x000c00eb8f4fb187 (missing bit 53) instead of the correct
0x002c00eb8f4fb187 (with bit 53 set).
Fix this by setting CPU_FTR_P11_PVR for all processors with
PVR >= PVR_POWER11 when ISA v3.1 support is detected in
cpufeatures_setup_start(). This approach ensures forward
compatibility with future processor generations.
Fixes: 96e266e3bcd6 ("KVM: PPC: Book3S HV: Add Power11 capability support for Nested PAPR guests")
Cc: stable@vger.kernel.org # v6.13+
Signed-off-by: Amit Machhiwal <amachhiw@linux.ibm.com>
Reviewed-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com>
Reviewed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260614173437.26352-1-amachhiw@linux.ibm.com
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/powerpc/kernel/dt_cpu_ftrs.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/dt_cpu_ftrs.c b/arch/powerpc/kernel/dt_cpu_ftrs.c index 3af6c06af02f..e5853daa6a48 100644 --- a/arch/powerpc/kernel/dt_cpu_ftrs.c +++ b/arch/powerpc/kernel/dt_cpu_ftrs.c @@ -704,6 +704,15 @@ static void __init cpufeatures_setup_start(u32 isa) if (isa >= ISA_V3_1) { cur_cpu_spec->cpu_features |= CPU_FTR_ARCH_31; cur_cpu_spec->cpu_user_features2 |= PPC_FEATURE2_ARCH_3_1; + + /* + * CPU_FTR_P11_PVR is a kernel-internal flag to identify + * Power11 and later processors. While ISA v3.1 is supported + * by Power10+, this flag specifically indicates Power11+ + * for code that needs to distinguish between P10 and P11. + */ + if (PVR_VER(mfspr(SPRN_PVR)) >= PVR_POWER11) + cur_cpu_spec->cpu_features |= CPU_FTR_P11_PVR; } } |