[RFC PATCH v4 10/39] KVM: arm64: Print a warning for unexpected faults on locked memslots
From: Alexandru Elisei <hidden>
Date: 2021-08-25 16:17:47
Also in:
kvmarm, lkml
Subsystem:
arm64 port (aarch64 architecture), kernel virtual machine for arm64 (kvm/arm64), the rest · Maintainers:
Catalin Marinas, Will Deacon, Marc Zyngier, Oliver Upton, Linus Torvalds
When userspace unmaps a VMA backing a memslot, the corresponding stage 2 address range gets unmapped via the MMU notifiers. This makes it possible to get stage 2 faults on a locked memslot, which might not be what userspace wants because the purpose of locking a memslot is to avoid stage 2 faults in the first place. Addresses being unmapped from stage 2 can happen from other reasons too, like bugs in the implementation of the lock memslot API, however unlikely that might seem. Let's try to make debugging easier by printing a warning when this happens. Signed-off-by: Alexandru Elisei <redacted> --- arch/arm64/kvm/mmu.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 3ab8eba808ae..d66d89c18045 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c@@ -1298,6 +1298,27 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) /* Userspace should not be able to register out-of-bounds IPAs */ VM_BUG_ON(fault_ipa >= kvm_phys_size(vcpu->kvm)); + if (memslot_is_locked(memslot)) { + const char *fault_type_str; + + if (kvm_vcpu_trap_is_exec_fault(vcpu)) + goto handle_fault; + + if (fault_status == FSC_ACCESS) + fault_type_str = "access"; + else if (write_fault && (memslot->arch.flags & KVM_MEMSLOT_LOCK_WRITE)) + fault_type_str = "write"; + else if (!write_fault) + fault_type_str = "read"; + else + goto handle_fault; + + kvm_warn_ratelimited("Unexpected L2 %s fault on locked memslot %d: IPA=%#llx, ESR_EL2=%#08x]\n", + fault_type_str, memslot->id, fault_ipa, + kvm_vcpu_get_esr(vcpu)); + } + +handle_fault: if (fault_status == FSC_ACCESS) { handle_access_fault(vcpu, fault_ipa); ret = 1;
--
2.33.0
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