From 644ffb02746690c0ebfe143e066f81c9bde2975e Mon Sep 17 00:00:00 2001 From: Venkat Rao Bagalkote Date: Wed, 9 Sep 2026 18:02:40 +0530 Subject: [PATCH] powerpc/interrupt: Use early_radix_enabled() in NMI real-mode guard radix_enabled() uses a jump label which is only valid after setup_feature_keys() is called. Before that point, on a pSeries hash guest, early_check_vec5() clears MMU_FTR_TYPE_RADIX in cur_cpu_spec->mmu_features, but the jump label has not yet been patched, so radix_enabled() incorrectly returns true. The dangerous usage window where it goes wrong in early_setup(): early_setup: configure_exceptions(); setup_feature_keys(); If an NMI occurs in this window, !radix_enabled() evaluates to false in DEFINE_INTERRUPT_HANDLER_NMI. The handler fails to skip NMI entry in real mode and attempts to access memory outside the Real Mode Area (RMA), hanging the boot. Since common interrupt wrappers do not have the context of early or late, using early_radix_enabled() is the safer option. It does a plain bitmask check against cur_cpu_spec->mmu_features and is correct at all times. Console logs from a pSeries HASH guest showing values across boot stages: [ 0.000000] DEBUG: after early_init_devtree: early_radix_enabled=0 radix_enabled=1 (mismatch means NMI real-mode check is unsafe!) [ 0.000000] DEBUG: after configure_exceptions (DANGEROUS WINDOW): early_radix_enabled=0 radix_enabled=1 [ 0.000000] DEBUG: after setup_feature_keys (jump labels initialized): early_radix_enabled=0 radix_enabled=0 (should now match!) [ 0.057124] DEBUG: post secondary CPU bringup: early_radix_enabled=0 radix_enabled=0 (should match!) Console logs from a RADIX guest showing values across boot stages: [ 0.000000] DEBUG: after early_init_devtree: early_radix_enabled=1 radix_enabled=1 (mismatch means NMI real-mode check is unsafe!) [ 0.000000] DEBUG: after configure_exceptions (DANGEROUS WINDOW): early_radix_enabled=1 radix_enabled=1 [ 0.000000] DEBUG: after setup_feature_keys (jump labels initialized): early_radix_enabled=1 radix_enabled=1 (should now match!) [ 0.057016] DEBUG: post secondary CPU bringup: early_radix_enabled=1 radix_enabled=1 (should match!) Add the missing #include in alphabetical order since early_radix_enabled() is declared there. Fixes: 8d0e21012743 ("powerpc/mce: Avoid nmi_enter/exit in real mode on pseries hash") Signed-off-by: Venkat Rao Bagalkote Reviewed-by: Mukesh Kumar Chaurasiya Reviewed-by: Shrikanth Hegde Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/20260909123240.58786-1-venkat88@linux.ibm.com --- arch/powerpc/include/asm/interrupt.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h index 1b45a49e9bed..355f6bbf9894 100644 --- a/arch/powerpc/include/asm/interrupt.h +++ b/arch/powerpc/include/asm/interrupt.h @@ -70,6 +70,7 @@ #include #include +#include #include #ifdef CONFIG_PPC_IRQ_SOFT_MASK_DEBUG @@ -290,7 +291,7 @@ interrupt_handler long func(struct pt_regs *regs) \ state = irqentry_nmi_enter(regs); \ } else if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && \ firmware_has_feature(FW_FEATURE_LPAR) && \ - !radix_enabled()) { \ + !early_radix_enabled()) { \ /* no nmi_entry for a pseries hash guest \ * taking a real mode exception */ \ } else if (IS_ENABLED(CONFIG_KASAN)) { \ @@ -307,7 +308,7 @@ interrupt_handler long func(struct pt_regs *regs) \ irqentry_nmi_exit(regs, state); \ } else if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && \ firmware_has_feature(FW_FEATURE_LPAR) && \ - !radix_enabled()) { \ + !early_radix_enabled()) { \ /* no nmi_exit for a pseries hash guest \ * taking a real mode exception */ \ } else if (IS_ENABLED(CONFIG_KASAN)) { \