[PATCH 45/52] KVM: PPC: Book3s HV: Implement get_dirty_log using hardware changed bit

Alexander Graf
2012-01-13T14:31:48Z

From: Paul Mackerras <paulus@samba.org>

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>
---
arch/powerpc/include/asm/kvm_book3s.h | 2 +
arch/powerpc/kvm/book3s.c | 39 ------------------
arch/powerpc/kvm/book3s_64_mmu_hv.c | 69 +++++++++++++++++++++++++++++++++
arch/powerpc/kvm/book3s_hv.c | 37 +++++++++++++++++
arch/powerpc/kvm/book3s_pr.c | 39 ++++++++++++++++++
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 33fdc09..3c3edee 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 6bf7e05..7d54f4e 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 926e2b9..783cd35 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 86c4191..0f1ddf0 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 2da6704..c193625 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)
{
--
1.6.0.2