On Wed, Mar 18, 2020 at 12:37:12PM -0400, Peter Xu wrote: > There's no good reason to use both the dirty bitmap logging and the > new dirty ring buffer to track dirty bits. We should be able to even > support both of them at the same time, but it could complicate things > which could actually help little. Let's simply make it the rule > before we enable dirty ring on any arch, that we don't allow these two > interfaces to be used together. > > The big world switch would be KVM_CAP_DIRTY_LOG_RING capability > enablement. That's where we'll switch from the default dirty logging > way to the dirty ring way. As long as kvm->dirty_ring_size is setup > correctly, we'll once and for all switch to the dirty ring buffer mode > for the current virtual machine. > > Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> > --- > Documentation/virt/kvm/api.rst | 7 +++++++ > virt/kvm/kvm_main.c | 12 ++++++++++++ > 2 files changed, 19 insertions(+) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 99ee9cfc20c4..8f3a83298d3f 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -6202,3 +6202,10 @@ make sure all the existing dirty gfns are flushed to the dirty rings. > > The dirty ring can gets full. When it happens, the KVM_RUN of the > vcpu will return with exit reason KVM_EXIT_DIRTY_LOG_FULL. > + > +NOTE: the KVM_CAP_DIRTY_LOG_RING capability and the new ioctl Leave off "new", it'll be stale a few months/years from now. > +KVM_RESET_DIRTY_RINGS are exclusive to the existing KVM_GET_DIRTY_LOG Did you mean "mutually exclusive with"? "exclusive to" would mean they can only be used by KVM_GET_DIRTY_LOG with doesn't match the next sentence. > +interface. After enabling KVM_CAP_DIRTY_LOG_RING with an acceptable > +dirty ring size, the virtual machine will switch to the dirty ring > +tracking mode, and KVM_GET_DIRTY_LOG, KVM_CLEAR_DIRTY_LOG ioctls will > +stop working. > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 54a1e893d17b..b289d3bddd5c 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1352,6 +1352,10 @@ int kvm_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log, > unsigned long n; > unsigned long any = 0; > > + /* Dirty ring tracking is exclusive to dirty log tracking */ > + if (kvm->dirty_ring_size) > + return -EINVAL; > + > *memslot = NULL; > *is_dirty = 0; > > @@ -1413,6 +1417,10 @@ static int kvm_get_dirty_log_protect(struct kvm *kvm, struct kvm_dirty_log *log) > unsigned long *dirty_bitmap_buffer; > bool flush; > > + /* Dirty ring tracking is exclusive to dirty log tracking */ > + if (kvm->dirty_ring_size) > + return -EINVAL; > + > as_id = log->slot >> 16; > id = (u16)log->slot; > if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS) > @@ -1521,6 +1529,10 @@ static int kvm_clear_dirty_log_protect(struct kvm *kvm, > unsigned long *dirty_bitmap_buffer; > bool flush; > > + /* Dirty ring tracking is exclusive to dirty log tracking */ > + if (kvm->dirty_ring_size) > + return -EINVAL; > + > as_id = log->slot >> 16; > id = (u16)log->slot; > if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS) > -- > 2.24.1 >
