[PATCH v18] arm64: mm: Handle Granule Protection Faults (GPFs)
From: Suzuki K Poulose <suzuki.poulose@arm.com>
Date: 2026-09-13 07:05:21
Also in:
kvm, kvmarm, linux-coco, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
From: Steven Price <steven.price@arm.com> If the host attempts to access granules that have been delegated for use in a realm these accesses will be caught and will trigger a Granule Protection Fault (GPF). A fault during a page walk signals a bug in the kernel and is handled by oopsing the kernel. A non-page walk fault could be caused by user space having access to a page which has been delegated to the kernel and will trigger a SIGBUS to allow debugging why user space is trying to access a delegated page. There is work in progress to unmap the guest_memfd backed private pages from the linear map. Until we get that support, we could get spurious GPFs from within the kernel, e.g., load_unaligned_zeropad(). So, try to fix them up for now. Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com> Reviewed-by: Gavin Shan <redacted> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Steven Price <steven.price@arm.com> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> --- Changes since v17: * Pass untagged address to die_kernel_fault() - Sashiko * Explicitly check !user_mode() for fixups - Catalin * Switch to BUS_OBJERR for si_code from SI_KERNEL - Catalin * Clarify the commit description about the upcoming work on unmapping guest_memfd backed pages from linear map Changes since v16: * Update the commit description to indicate why we try to fixup GPFs Changes since v10: * Don't call arm64_notify_die() in do_gpf() but simply return 1. Changes since v2: * Include missing "Granule Protection Fault at level -1" --- arch/arm64/mm/fault.c | 30 ++++++++++++++++++++++++------ 1 file changed, 24 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 75c3e463df2ef..dc3a87902a60c 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c@@ -914,6 +914,24 @@ static int do_tag_check_fault(unsigned long far, unsigned long esr, return 0; } +static int do_gpf_ptw(unsigned long far, unsigned long esr, struct pt_regs *regs) +{ + const struct fault_info *inf = esr_to_fault_info(esr); + unsigned long addr = untagged_addr(far); + + die_kernel_fault(inf->name, addr, esr, regs); + return 0; +} + +static int do_gpf(unsigned long far, unsigned long esr, struct pt_regs *regs) +{ + if (!user_mode(regs) && !is_el1_instruction_abort(esr) && + fixup_exception(regs, esr)) + return 0; + + return 1; +} + static const struct fault_info fault_info[] = { { do_bad, SIGKILL, SI_KERNEL, "ttbr address size fault" }, { do_bad, SIGKILL, SI_KERNEL, "level 1 address size fault" },
@@ -950,12 +968,12 @@ static const struct fault_info fault_info[] = { { do_bad, SIGKILL, SI_KERNEL, "unknown 32" }, { do_alignment_fault, SIGBUS, BUS_ADRALN, "alignment fault" }, { do_bad, SIGKILL, SI_KERNEL, "unknown 34" }, - { do_bad, SIGKILL, SI_KERNEL, "unknown 35" }, - { do_bad, SIGKILL, SI_KERNEL, "unknown 36" }, - { do_bad, SIGKILL, SI_KERNEL, "unknown 37" }, - { do_bad, SIGKILL, SI_KERNEL, "unknown 38" }, - { do_bad, SIGKILL, SI_KERNEL, "unknown 39" }, - { do_bad, SIGKILL, SI_KERNEL, "unknown 40" }, + { do_gpf_ptw, SIGKILL, SI_KERNEL, "level -1 granule protection fault (translation table walk)" }, + { do_gpf_ptw, SIGKILL, SI_KERNEL, "level 0 granule protection fault (translation table walk)" }, + { do_gpf_ptw, SIGKILL, SI_KERNEL, "level 1 granule protection fault (translation table walk)" }, + { do_gpf_ptw, SIGKILL, SI_KERNEL, "level 2 granule protection fault (translation table walk)" }, + { do_gpf_ptw, SIGKILL, SI_KERNEL, "level 3 granule protection fault (translation table walk)" }, + { do_gpf, SIGBUS, BUS_OBJERR, "granule protection fault" }, { do_bad, SIGKILL, SI_KERNEL, "level -1 address size fault" }, { do_bad, SIGKILL, SI_KERNEL, "unknown 42" }, { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level -1 translation fault" },
--
2.43.0