On Tue, Apr 16, 2024 at 04:00:56PM +0100, Jonathan Cameron wrote: > On Mon, 15 Apr 2024 10:37:00 -0700 > fan <nifan....@gmail.com> wrote: > > > On Fri, Apr 12, 2024 at 06:54:42PM -0400, Gregory Price wrote: > > > On Mon, Mar 25, 2024 at 12:02:28PM -0700, nifan....@gmail.com wrote: > > > > From: Fan Ni <fan...@samsung.com> > > > > > > > > All dpa ranges in the DC regions are invalid to access until an extent > > > > covering the range has been added. Add a bitmap for each region to > > > > record whether a DC block in the region has been backed by DC extent. > > > > For the bitmap, a bit in the bitmap represents a DC block. When a DC > > > > extent is added, all the bits of the blocks in the extent will be set, > > > > which will be cleared when the extent is released. > > > > > > > > Reviewed-by: Jonathan Cameron <jonathan.came...@huawei.com> > > > > Signed-off-by: Fan Ni <fan...@samsung.com> > > > > --- > > > > hw/cxl/cxl-mailbox-utils.c | 6 +++ > > > > hw/mem/cxl_type3.c | 76 +++++++++++++++++++++++++++++++++++++ > > > > include/hw/cxl/cxl_device.h | 7 ++++ > > > > 3 files changed, 89 insertions(+) > > > > > > > > diff --git a/hw/cxl/cxl-mailbox-utils.c b/hw/cxl/cxl-mailbox-utils.c > > > > index 7094e007b9..a0d2239176 100644 > > > > --- a/hw/cxl/cxl-mailbox-utils.c > > > > +++ b/hw/cxl/cxl-mailbox-utils.c > > > > @@ -1620,6 +1620,7 @@ static CXLRetCode cmd_dcd_add_dyn_cap_rsp(const > > > > struct cxl_cmd *cmd, > > > > > > > > cxl_insert_extent_to_extent_list(extent_list, dpa, len, NULL, > > > > 0); > > > > ct3d->dc.total_extent_count += 1; > > > > + ct3_set_region_block_backed(ct3d, dpa, len); > > > > > > > > ent = QTAILQ_FIRST(&ct3d->dc.extents_pending); > > > > cxl_remove_extent_from_extent_list(&ct3d->dc.extents_pending, > > > > ent); > > > > > > while looking at the MHD code, we had decided to "reserve" the blocks in > > > the bitmap in the call to `qmp_cxl_process_dynamic_capacity` in order to > > > prevent a potential double-allocation (basically we need to sanity check > > > that two hosts aren't reserving the region PRIOR to the host being > > > notified). > > > > > > I did not see any checks in the `qmp_cxl_process_dynamic_capacity` path > > > to prevent pending extents from being double-allocated. Is this an > > > explicit choice? > > > > > > I can see, for example, why you may want to allow the following in the > > > pending list: [Add X, Remove X, Add X]. I just want to know if this is > > > intentional or not. If not, you may consider adding a pending check > > > during the sanity check phase of `qmp_cxl_process_dynamic_capacity` > > > > > > ~Gregory > > > > First, for remove request, pending list is not involved. See cxl r3.1, > > 9.13.3.3. Pending basically means "pending to add". > > So for the above example, in the pending list, you can see [Add x, add x] > > if the > > event is not processed in time. > > Second, from the spec, I cannot find any text saying we cannot issue > > another add extent X if it is still pending. > > I think there is text saying that the capacity is not released for reuse > by the device until it receives a response from the host. Whilst > it's not explicit on offers to the same host, I'm not sure that matters. > So I don't think it is suppose to queue multiple extents... > >
It definitely should not release capacity until it receives a response, because the host could tell the device to kick rocks (which would be reasonable under a variety of circumstances). ~Gregory
