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>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 71beb27597fd..bd254779d1cc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3190,6 +3190,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
                 }
                 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);