1 files changed, 22 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
index fc3da3208fda..7a57ea49172d 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -600,6 +600,28 @@ long kvmppc_h_protect(struct kvm_vcpu *vcpu, unsigned long flags,
                         asm volatile("tlbiel %0" : : "r" (rb));
                         asm volatile("ptesync" : : : "memory");
                 }
+                /*
+                 * If the host has this page as readonly but the guest
+                 * wants to make it read/write, reduce the permissions.
+                 * Checking the host permissions involves finding the
+                 * memslot and then the Linux PTE for the page.
+                 */
+                if (hpte_is_writable(r) && kvm->arch.using_mmu_notifiers) {
+                        unsigned long psize, gfn, hva;
+                        struct kvm_memory_slot *memslot;
+                        pgd_t *pgdir = vcpu->arch.pgdir;
+                        pte_t pte;
+
+                        psize = hpte_page_size(v, r);
+                        gfn = ((r & HPTE_R_RPN) & ~(psize - 1)) >> PAGE_SHIFT;
+                        memslot = __gfn_to_memslot(kvm_memslots(kvm), gfn);
+                        if (memslot) {
+                                hva = __gfn_to_hva_memslot(memslot, gfn);
+                                pte = lookup_linux_pte(pgdir, hva, 1, &psize);
+                                if (pte_present(pte) && !pte_write(pte))
+                                        r = hpte_make_readonly(r);
+                        }
+                }
         }
         hpte[1] = r;
         eieio();