KVM: add support for change_pte mmu notifiers

this is needed for kvm if it want ksm to directly map pages into its
shadow page tables.

[marcelo: cast pfn assignment to u64]

Signed-off-by: Izik Eidus <ieidus@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

3 files changed, 68 insertions, 9 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 3be000435fad..d83892226f73 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -796,6 +796,7 @@ asmlinkage void kvm_handle_fault_on_reboot(void);
 #define KVM_ARCH_WANT_MMU_NOTIFIER
 int kvm_unmap_hva(struct kvm *kvm, unsigned long hva);
 int kvm_age_hva(struct kvm *kvm, unsigned long hva);
+void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);
 int cpuid_maxphyaddr(struct kvm_vcpu *vcpu);
 int kvm_cpu_has_interrupt(struct kvm_vcpu *vcpu);
 int kvm_arch_interrupt_allowed(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 5cd8b4ec3a01..685a4ffac8e6 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -748,7 +748,7 @@ static int rmap_write_protect(struct kvm *kvm, u64 gfn)
         return write_protected;
 }
 
-static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp)
+static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp, u64 data)
 {
         u64 *spte;
         int need_tlb_flush = 0;
@@ -763,8 +763,45 @@ static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp)
         return need_tlb_flush;
 }
 
-static int kvm_handle_hva(struct kvm *kvm, unsigned long hva,
-                          int (*handler)(struct kvm *kvm, unsigned long *rmapp))
+static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp, u64 data)
+{
+        int need_flush = 0;
+        u64 *spte, new_spte;
+        pte_t *ptep = (pte_t *)data;
+        pfn_t new_pfn;
+
+        WARN_ON(pte_huge(*ptep));
+        new_pfn = pte_pfn(*ptep);
+        spte = rmap_next(kvm, rmapp, NULL);
+        while (spte) {
+                BUG_ON(!is_shadow_present_pte(*spte));
+                rmap_printk("kvm_set_pte_rmapp: spte %p %llx\n", spte, *spte);
+                need_flush = 1;
+                if (pte_write(*ptep)) {
+                        rmap_remove(kvm, spte);
+                        __set_spte(spte, shadow_trap_nonpresent_pte);
+                        spte = rmap_next(kvm, rmapp, NULL);
+                } else {
+                        new_spte = *spte &~ (PT64_BASE_ADDR_MASK);
+                        new_spte |= (u64)new_pfn << PAGE_SHIFT;
+
+                        new_spte &= ~PT_WRITABLE_MASK;
+                        new_spte &= ~SPTE_HOST_WRITEABLE;
+                        if (is_writeble_pte(*spte))
+                                kvm_set_pfn_dirty(spte_to_pfn(*spte));
+                        __set_spte(spte, new_spte);
+                        spte = rmap_next(kvm, rmapp, spte);
+                }
+        }
+        if (need_flush)
+                kvm_flush_remote_tlbs(kvm);
+
+        return 0;
+}
+
+static int kvm_handle_hva(struct kvm *kvm, unsigned long hva, u64 data,
+                          int (*handler)(struct kvm *kvm, unsigned long *rmapp,
+                                         u64 data))
 {
         int i, j;
         int retval = 0;
@@ -786,13 +823,15 @@ static int kvm_handle_hva(struct kvm *kvm, unsigned long hva,
                 if (hva >= start && hva < end) {
                         gfn_t gfn_offset = (hva - start) >> PAGE_SHIFT;
 
-                        retval |= handler(kvm, &memslot->rmap[gfn_offset]);
+                        retval |= handler(kvm, &memslot->rmap[gfn_offset],
+                                          data);
 
                         for (j = 0; j < KVM_NR_PAGE_SIZES - 1; ++j) {
                                 int idx = gfn_offset;
                                 idx /= KVM_PAGES_PER_HPAGE(PT_DIRECTORY_LEVEL + j);
                                 retval |= handler(kvm,
-                                        &memslot->lpage_info[j][idx].rmap_pde);
+                                        &memslot->lpage_info[j][idx].rmap_pde,
+                                        data);
                         }
                 }
         }
@@ -802,10 +841,15 @@ static int kvm_handle_hva(struct kvm *kvm, unsigned long hva,
 
 int kvm_unmap_hva(struct kvm *kvm, unsigned long hva)
 {
-        return kvm_handle_hva(kvm, hva, kvm_unmap_rmapp);
+        return kvm_handle_hva(kvm, hva, 0, kvm_unmap_rmapp);
+}
+
+void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
+{
+        kvm_handle_hva(kvm, hva, (u64)&pte, kvm_set_pte_rmapp);
 }
 
-static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp)
+static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp, u64 data)
 {
         u64 *spte;
         int young = 0;
@@ -841,13 +885,13 @@ static void rmap_recycle(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
         gfn = unalias_gfn(vcpu->kvm, gfn);
         rmapp = gfn_to_rmap(vcpu->kvm, gfn, sp->role.level);
 
-        kvm_unmap_rmapp(vcpu->kvm, rmapp);
+        kvm_unmap_rmapp(vcpu->kvm, rmapp, 0);
         kvm_flush_remote_tlbs(vcpu->kvm);
 }
 
 int kvm_age_hva(struct kvm *kvm, unsigned long hva)
 {
-        return kvm_handle_hva(kvm, hva, kvm_age_rmapp);
+        return kvm_handle_hva(kvm, hva, 0, kvm_age_rmapp);
 }
 
 #ifdef MMU_DEBUG
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e79c54034bcd..b7c78a403dc2 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -850,6 +850,19 @@ static void kvm_mmu_notifier_invalidate_page(struct mmu_notifier *mn,
 
 }
 
+static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn,
+                                        struct mm_struct *mm,
+                                        unsigned long address,
+                                        pte_t pte)
+{
+        struct kvm *kvm = mmu_notifier_to_kvm(mn);
+
+        spin_lock(&kvm->mmu_lock);
+        kvm->mmu_notifier_seq++;
+        kvm_set_spte_hva(kvm, address, pte);
+        spin_unlock(&kvm->mmu_lock);
+}
+
 static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
                                                     struct mm_struct *mm,
                                                     unsigned long start,
@@ -929,6 +942,7 @@ static const struct mmu_notifier_ops kvm_mmu_notifier_ops = {
         .invalidate_range_start = kvm_mmu_notifier_invalidate_range_start,
         .invalidate_range_end   = kvm_mmu_notifier_invalidate_range_end,
         .clear_flush_young      = kvm_mmu_notifier_clear_flush_young,
+        .change_pte             = kvm_mmu_notifier_change_pte,
         .release                = kvm_mmu_notifier_release,
 };
 #endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */