KVM: PPC: Book3s HV: Implement get_dirty_log using hardware changed bit

This changes the implementation of kvm_vm_ioctl_get_dirty_log() for
Book3s HV guests to use the hardware C (changed) bits in the guest
hashed page table.  Since this makes the implementation quite different
from the Book3s PR case, this moves the existing implementation from
book3s.c to book3s_pr.c and creates a new implementation in book3s_hv.c.
That implementation calls kvmppc_hv_get_dirty_log() to do the actual
work by calling kvm_test_clear_dirty on each page.  It iterates over
the HPTEs, clearing the C bit if set, and returns 1 if any C bit was
set (including the saved C bit in the rmap entry).

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

5 files changed, 147 insertions, 39 deletions

diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
index 33fdc09508a1..3c3edee672aa 100644
--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/arch/powerpc/include/asm/kvm_book3s.h
@@ -156,6 +156,8 @@ extern long kvmppc_virtmode_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
                         long pte_index, unsigned long pteh, unsigned long ptel);
 extern long kvmppc_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
                         long pte_index, unsigned long pteh, unsigned long ptel);
+extern long kvmppc_hv_get_dirty_log(struct kvm *kvm,
+                        struct kvm_memory_slot *memslot);
 
 extern void kvmppc_entry_trampoline(void);
 extern void kvmppc_hv_entry_trampoline(void);
diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index 6bf7e0582c5a..7d54f4ed6d96 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -477,45 +477,6 @@ int kvm_arch_vcpu_ioctl_translate(struct kvm_vcpu *vcpu,
         return 0;
 }
 
-/*
- * Get (and clear) the dirty memory log for a memory slot.
- */
-int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
-                                      struct kvm_dirty_log *log)
-{
-        struct kvm_memory_slot *memslot;
-        struct kvm_vcpu *vcpu;
-        ulong ga, ga_end;
-        int is_dirty = 0;
-        int r;
-        unsigned long n;
-
-        mutex_lock(&kvm->slots_lock);
-
-        r = kvm_get_dirty_log(kvm, log, &is_dirty);
-        if (r)
-                goto out;
-
-        /* If nothing is dirty, don't bother messing with page tables. */
-        if (is_dirty) {
-                memslot = id_to_memslot(kvm->memslots, log->slot);
-
-                ga = memslot->base_gfn << PAGE_SHIFT;
-                ga_end = ga + (memslot->npages << PAGE_SHIFT);
-
-                kvm_for_each_vcpu(n, vcpu, kvm)
-                        kvmppc_mmu_pte_pflush(vcpu, ga, ga_end);
-
-                n = kvm_dirty_bitmap_bytes(memslot);
-                memset(memslot->dirty_bitmap, 0, n);
-        }
-
-        r = 0;
-out:
-        mutex_unlock(&kvm->slots_lock);
-        return r;
-}
-
 void kvmppc_decrementer_func(unsigned long data)
 {
         struct kvm_vcpu *vcpu = (struct kvm_vcpu *)data;
diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 926e2b92bdab..783cd3510c93 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -870,6 +870,75 @@ void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
         kvm_handle_hva(kvm, hva, kvm_unmap_rmapp);
 }
 
+static int kvm_test_clear_dirty(struct kvm *kvm, unsigned long *rmapp)
+{
+        struct revmap_entry *rev = kvm->arch.revmap;
+        unsigned long head, i, j;
+        unsigned long *hptep;
+        int ret = 0;
+
+ retry:
+        lock_rmap(rmapp);
+        if (*rmapp & KVMPPC_RMAP_CHANGED) {
+                *rmapp &= ~KVMPPC_RMAP_CHANGED;
+                ret = 1;
+        }
+        if (!(*rmapp & KVMPPC_RMAP_PRESENT)) {
+                unlock_rmap(rmapp);
+                return ret;
+        }
+
+        i = head = *rmapp & KVMPPC_RMAP_INDEX;
+        do {
+                hptep = (unsigned long *) (kvm->arch.hpt_virt + (i << 4));
+                j = rev[i].forw;
+
+                if (!(hptep[1] & HPTE_R_C))
+                        continue;
+
+                if (!try_lock_hpte(hptep, HPTE_V_HVLOCK)) {
+                        /* unlock rmap before spinning on the HPTE lock */
+                        unlock_rmap(rmapp);
+                        while (hptep[0] & HPTE_V_HVLOCK)
+                                cpu_relax();
+                        goto retry;
+                }
+
+                /* Now check and modify the HPTE */
+                if ((hptep[0] & HPTE_V_VALID) && (hptep[1] & HPTE_R_C)) {
+                        /* need to make it temporarily absent to clear C */
+                        hptep[0] |= HPTE_V_ABSENT;
+                        kvmppc_invalidate_hpte(kvm, hptep, i);
+                        hptep[1] &= ~HPTE_R_C;
+                        eieio();
+                        hptep[0] = (hptep[0] & ~HPTE_V_ABSENT) | HPTE_V_VALID;
+                        rev[i].guest_rpte |= HPTE_R_C;
+                        ret = 1;
+                }
+                hptep[0] &= ~HPTE_V_HVLOCK;
+        } while ((i = j) != head);
+
+        unlock_rmap(rmapp);
+        return ret;
+}
+
+long kvmppc_hv_get_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
+{
+        unsigned long i;
+        unsigned long *rmapp, *map;
+
+        preempt_disable();
+        rmapp = memslot->rmap;
+        map = memslot->dirty_bitmap;
+        for (i = 0; i < memslot->npages; ++i) {
+                if (kvm_test_clear_dirty(kvm, rmapp))
+                        __set_bit_le(i, map);
+                ++rmapp;
+        }
+        preempt_enable();
+        return 0;
+}
+
 void *kvmppc_pin_guest_page(struct kvm *kvm, unsigned long gpa,
                             unsigned long *nb_ret)
 {
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 86c4191cb75b..0f1ddf0ec032 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1072,6 +1072,43 @@ long kvm_vm_ioctl_allocate_rma(struct kvm *kvm, struct kvm_allocate_rma *ret)
         return fd;
 }
 
+/*
+ * Get (and clear) the dirty memory log for a memory slot.
+ */
+int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
+{
+        struct kvm_memory_slot *memslot;
+        int r;
+        unsigned long n;
+
+        mutex_lock(&kvm->slots_lock);
+
+        r = -EINVAL;
+        if (log->slot >= KVM_MEMORY_SLOTS)
+                goto out;
+
+        memslot = id_to_memslot(kvm->memslots, log->slot);
+        r = -ENOENT;
+        if (!memslot->dirty_bitmap)
+                goto out;
+
+        n = kvm_dirty_bitmap_bytes(memslot);
+        memset(memslot->dirty_bitmap, 0, n);
+
+        r = kvmppc_hv_get_dirty_log(kvm, memslot);
+        if (r)
+                goto out;
+
+        r = -EFAULT;
+        if (copy_to_user(log->dirty_bitmap, memslot->dirty_bitmap, n))
+                goto out;
+
+        r = 0;
+out:
+        mutex_unlock(&kvm->slots_lock);
+        return r;
+}
+
 static unsigned long slb_pgsize_encoding(unsigned long psize)
 {
         unsigned long senc = 0;
diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index 2da670405727..c193625d5289 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -1056,6 +1056,45 @@ out:
         return ret;
 }
 
+/*
+ * Get (and clear) the dirty memory log for a memory slot.
+ */
+int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
+                                      struct kvm_dirty_log *log)
+{
+        struct kvm_memory_slot *memslot;
+        struct kvm_vcpu *vcpu;
+        ulong ga, ga_end;
+        int is_dirty = 0;
+        int r;
+        unsigned long n;
+
+        mutex_lock(&kvm->slots_lock);
+
+        r = kvm_get_dirty_log(kvm, log, &is_dirty);
+        if (r)
+                goto out;
+
+        /* If nothing is dirty, don't bother messing with page tables. */
+        if (is_dirty) {
+                memslot = id_to_memslot(kvm->memslots, log->slot);
+
+                ga = memslot->base_gfn << PAGE_SHIFT;
+                ga_end = ga + (memslot->npages << PAGE_SHIFT);
+
+                kvm_for_each_vcpu(n, vcpu, kvm)
+                        kvmppc_mmu_pte_pflush(vcpu, ga, ga_end);
+
+                n = kvm_dirty_bitmap_bytes(memslot);
+                memset(memslot->dirty_bitmap, 0, n);
+        }
+
+        r = 0;
+out:
+        mutex_unlock(&kvm->slots_lock);
+        return r;
+}
+
 int kvmppc_core_prepare_memory_region(struct kvm *kvm,
                                       struct kvm_userspace_memory_region *mem)
 {