Ard Biesheuvel 2c340aab54 x86/efi: Restore IRQ state in EFI page fault handler ... The kernel's softirq API does not permit re-enabling softirqs while IRQs are disabled. The reason for this is that local_bh_enable() will not only re-enable delivery of softirqs over the back of IRQs, it will also handle any pending softirqs immediately, regardless of whether IRQs are enabled at that point. For this reason, commit d021985504 ("x86/fpu: Improve crypto performance by making kernel-mode FPU reliably usable in softirqs") disables softirqs only when IRQs are enabled, as it is not permitted otherwise, but also unnecessary, given that asynchronous softirq delivery never happens to begin with while IRQs are disabled. However, this does mean that entering a kernel mode FPU section with IRQs enabled and leaving it with IRQs disabled leads to problems, as identified by Sashiko [0]: the EFI page fault handler is called from page_fault_oops() with IRQs disabled, and thus ends the kernel mode FPU section with IRQs disabled as well, regardless of whether IRQs were enabled when it was started. This may result in schedule() being called with a non-zero preempt_count, causing a BUG(). So take care to re-enable IRQs when handling any EFI page faults if they were taken with IRQs enabled. [0] https://sashiko.dev/#/patchset/20260430074107.27051-1-ivan.hu%40canonical.com Cc: Eric Biggers <ebiggers@kernel.org> Cc: Ivan Hu <ivan.hu@canonical.com> Cc: x86@kernel.org Cc: <stable@vger.kernel.org> Fixes: d021985504 ("x86/fpu: Improve crypto performance by making kernel-mode FPU reliably usable in softirqs") Reviewed-by: Eric Biggers <ebiggers@kernel.org> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>		2026-05-05 09:31:28 +02:00
..
efi_32.c	efi/x86: Move EFI runtime call setup/teardown helpers out of line	2023-09-11 06:37:50 +00:00
efi_64.c	x86/efi: Disable LASS while executing runtime services	2026-03-03 09:49:45 -08:00
efi_stub_32.S	x86: Prepare asm files for straight-line-speculation	2021-12-08 12:25:37 +01:00
efi_stub_64.S	objtool: Validate kCFI calls	2025-08-18 14:23:09 +02:00
efi_thunk_64.S	efi/x86-mixed: move unmitigated RET into .rodata	2022-08-16 09:28:05 +02:00
efi.c	integrity-v7.1	2026-04-17 15:42:01 -07:00
Makefile	x86/efi: Drop support for fake EFI memory maps	2024-07-02 00:26:24 +02:00
memmap.c	memblock, treewide: make memblock_free() handle late freeing	2026-04-01 11:20:15 +03:00
quirks.c	x86/efi: Restore IRQ state in EFI page fault handler	2026-05-05 09:31:28 +02:00
runtime-map.c	Convert 'alloc_obj' family to use the new default GFP_KERNEL argument	2026-02-21 17:09:51 -08:00