KVM: Add memory slot versioning and use it to provide fast guest write interface
Keep track of memslots changes by keeping generation number in memslots
structure. Provide kvm_write_guest_cached() function that skips
gfn_to_hva() translation if memslots was not changed since previous
invocation.
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 71beb27..bd25477 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3190,6 +3190,7 @@
}
memcpy(slots, kvm->memslots, sizeof(struct kvm_memslots));
slots->memslots[log->slot].dirty_bitmap = dirty_bitmap;
+ slots->generation++;
old_slots = kvm->memslots;
rcu_assign_pointer(kvm->memslots, slots);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index e56acc7..e674820 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -199,6 +199,7 @@
struct kvm_memslots {
int nmemslots;
+ u64 generation;
struct kvm_memory_slot memslots[KVM_MEMORY_SLOTS +
KVM_PRIVATE_MEM_SLOTS];
};
@@ -352,12 +353,18 @@
int offset, int len);
int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
unsigned long len);
+int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
+ void *data, unsigned long len);
+int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
+ gpa_t gpa);
int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len);
int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len);
struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn);
int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn);
unsigned long kvm_host_page_size(struct kvm *kvm, gfn_t gfn);
void mark_page_dirty(struct kvm *kvm, gfn_t gfn);
+void mark_page_dirty_in_slot(struct kvm *kvm, struct kvm_memory_slot *memslot,
+ gfn_t gfn);
void kvm_vcpu_block(struct kvm_vcpu *vcpu);
void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu);
diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
index 7ac0d4ee..fa7cc72 100644
--- a/include/linux/kvm_types.h
+++ b/include/linux/kvm_types.h
@@ -67,4 +67,11 @@
u32 dest_id;
};
+struct gfn_to_hva_cache {
+ u64 generation;
+ gpa_t gpa;
+ unsigned long hva;
+ struct kvm_memory_slot *memslot;
+};
+
#endif /* __KVM_TYPES_H__ */
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 75fd590..228f00f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -687,6 +687,7 @@
memcpy(slots, kvm->memslots, sizeof(struct kvm_memslots));
if (mem->slot >= slots->nmemslots)
slots->nmemslots = mem->slot + 1;
+ slots->generation++;
slots->memslots[mem->slot].flags |= KVM_MEMSLOT_INVALID;
old_memslots = kvm->memslots;
@@ -721,6 +722,7 @@
memcpy(slots, kvm->memslots, sizeof(struct kvm_memslots));
if (mem->slot >= slots->nmemslots)
slots->nmemslots = mem->slot + 1;
+ slots->generation++;
/* actual memory is freed via old in kvm_free_physmem_slot below */
if (!npages) {
@@ -851,10 +853,10 @@
}
EXPORT_SYMBOL_GPL(kvm_is_error_hva);
-struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
+static struct kvm_memory_slot *__gfn_to_memslot(struct kvm_memslots *slots,
+ gfn_t gfn)
{
int i;
- struct kvm_memslots *slots = kvm_memslots(kvm);
for (i = 0; i < slots->nmemslots; ++i) {
struct kvm_memory_slot *memslot = &slots->memslots[i];
@@ -865,6 +867,11 @@
}
return NULL;
}
+
+struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
+{
+ return __gfn_to_memslot(kvm_memslots(kvm), gfn);
+}
EXPORT_SYMBOL_GPL(gfn_to_memslot);
int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
@@ -927,12 +934,9 @@
return memslot - slots->memslots;
}
-static unsigned long gfn_to_hva_many(struct kvm *kvm, gfn_t gfn,
+static unsigned long gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t gfn,
gfn_t *nr_pages)
{
- struct kvm_memory_slot *slot;
-
- slot = gfn_to_memslot(kvm, gfn);
if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
return bad_hva();
@@ -944,7 +948,7 @@
unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
{
- return gfn_to_hva_many(kvm, gfn, NULL);
+ return gfn_to_hva_many(gfn_to_memslot(kvm, gfn), gfn, NULL);
}
EXPORT_SYMBOL_GPL(gfn_to_hva);
@@ -1054,7 +1058,7 @@
unsigned long addr;
gfn_t entry;
- addr = gfn_to_hva_many(kvm, gfn, &entry);
+ addr = gfn_to_hva_many(gfn_to_memslot(kvm, gfn), gfn, &entry);
if (kvm_is_error_hva(addr))
return -1;
@@ -1238,6 +1242,47 @@
return 0;
}
+int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
+ gpa_t gpa)
+{
+ struct kvm_memslots *slots = kvm_memslots(kvm);
+ int offset = offset_in_page(gpa);
+ gfn_t gfn = gpa >> PAGE_SHIFT;
+
+ ghc->gpa = gpa;
+ ghc->generation = slots->generation;
+ ghc->memslot = __gfn_to_memslot(slots, gfn);
+ ghc->hva = gfn_to_hva_many(ghc->memslot, gfn, NULL);
+ if (!kvm_is_error_hva(ghc->hva))
+ ghc->hva += offset;
+ else
+ return -EFAULT;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kvm_gfn_to_hva_cache_init);
+
+int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
+ void *data, unsigned long len)
+{
+ struct kvm_memslots *slots = kvm_memslots(kvm);
+ int r;
+
+ if (slots->generation != ghc->generation)
+ kvm_gfn_to_hva_cache_init(kvm, ghc, ghc->gpa);
+
+ if (kvm_is_error_hva(ghc->hva))
+ return -EFAULT;
+
+ r = copy_to_user((void __user *)ghc->hva, data, len);
+ if (r)
+ return -EFAULT;
+ mark_page_dirty_in_slot(kvm, ghc->memslot, ghc->gpa >> PAGE_SHIFT);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kvm_write_guest_cached);
+
int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len)
{
return kvm_write_guest_page(kvm, gfn, empty_zero_page, offset, len);
@@ -1263,11 +1308,9 @@
}
EXPORT_SYMBOL_GPL(kvm_clear_guest);
-void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
+void mark_page_dirty_in_slot(struct kvm *kvm, struct kvm_memory_slot *memslot,
+ gfn_t gfn)
{
- struct kvm_memory_slot *memslot;
-
- memslot = gfn_to_memslot(kvm, gfn);
if (memslot && memslot->dirty_bitmap) {
unsigned long rel_gfn = gfn - memslot->base_gfn;
@@ -1275,6 +1318,14 @@
}
}
+void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
+{
+ struct kvm_memory_slot *memslot;
+
+ memslot = gfn_to_memslot(kvm, gfn);
+ mark_page_dirty_in_slot(kvm, memslot, gfn);
+}
+
/*
* The vCPU has executed a HLT instruction with in-kernel mode enabled.
*/