[PATCH v7 04/12] Add memory slot versioning and use it to provide fast guest write interface

Gleb Natapov
2010-10-14T09:22:48Z

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>
---
include/linux/kvm_host.h | 7 ++++
include/linux/kvm_types.h | 7 ++++
virt/kvm/kvm_main.c | 75 +++++++++++++++++++++++++++++++++++++-------
3 files changed, 77 insertions(+), 12 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 9a9b017..dda88f2 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -199,6 +199,7 @@ struct kvm_irq_routing_table {};

struct kvm_memslots {
int nmemslots;
+ u64 generation;
struct kvm_memory_slot memslots[KVM_MEMORY_SLOTS +
KVM_PRIVATE_MEM_SLOTS];
};
@@ -352,12 +353,18 @@ int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn, const void *data,
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 7ac0d4e..fa7cc72 100644
--- a/include/linux/kvm_types.h
+++ b/include/linux/kvm_types.h
@@ -67,4 +67,11 @@ struct kvm_lapic_irq {
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 238079e..5d57ec9 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -687,6 +687,7 @@ skip_lpage:
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;
@@ -723,6 +724,7 @@ skip_lpage:
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) {
@@ -853,10 +855,10 @@ int kvm_is_error_hva(unsigned long addr)
}
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];
@@ -867,6 +869,11 @@ struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
}
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)
@@ -929,12 +936,9 @@ int memslot_id(struct kvm *kvm, gfn_t gfn)
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();

@@ -946,7 +950,7 @@ static unsigned long gfn_to_hva_many(struct kvm *kvm, gfn_t gfn,

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);

@@ -1063,7 +1067,7 @@ int gfn_to_page_many_atomic(struct kvm *kvm, gfn_t gfn, struct page **pages,
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;

@@ -1247,6 +1251,47 @@ int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
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);
@@ -1272,11 +1317,9 @@ int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len)
}
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;

@@ -1284,6 +1327,14 @@ void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
}
}

+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.
*/