Since cd758a9b57ee "KVM: PPC: Book3S HV: Use __gfn_to_pfn_memslot in HPT page fault handler", it's been possible in fairly rare circumstances to load a non-present PTE in kvmppc_book3s_hv_page_fault() when running a guest on a POWER8 host.
Because that case wasn't checked for, we could misinterpret the non-present PTE as being a cache-inhibited PTE. That could mismatch with the corresponding hash PTE, which would cause the function to fail with -EFAULT a little further down. That would propagate up to the KVM_RUN ioctl() generally causing the KVM userspace (usually qemu) to fall over. This addresses the problem by catching that case and returning to the guest instead. Fixes: cd758a9b57ee "KVM: PPC: Book3S HV: Use __gfn_to_pfn_memslot in HPT page fault handler" Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1820402 Suggested-by: Paul Mackerras <pau...@samba.org> Signed-off-by: David Gibson <da...@gibson.dropbear.id.au> --- arch/powerpc/kvm/book3s_64_mmu_hv.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c index 6404df613ea3..394fca8e630a 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c @@ -616,6 +616,11 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu, } pte = *ptep; local_irq_enable(); + if (!pte_present(pte)) { + if (page) + put_page(page); + return RESUME_GUEST; + } hpa = pte_pfn(pte) << PAGE_SHIFT; pte_size = PAGE_SIZE; if (shift) -- 2.25.2
