Messages in this thread | | | Date | Tue, 15 Nov 2022 10:09:57 -0800 | From | Dan Williams <> | Subject | Re: [PATCH v3 4/9] cxl/mem: Skip intermediate port enumeration of restricted endpoints (RCDs) |
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Robert Richter wrote: > On 14.11.22 16:24:06, Dan Williams wrote: > > Robert Richter wrote: > > > When an endpoint is found, all ports in beetween the endpoint and the > > > CXL host bridge need to be created. In the RCH case there are no ports > > > in between a host bridge and the endpoint. Skip the enumeration of > > > intermediate ports. > > > > > > The port enumeration does not only create all ports, it also > > > initializes the endpoint chain by adding the endpoint to every > > > downstream port up to the root bridge. This must be done also in RCD > > > mode, but is much more simple as the endpoint only needs to be added > > > to the host bridge's dport. > > > > > > Note: For endpoint removal the cxl_detach_ep() is not needed as it is > > > released in cxl_port_release(). > > > > > > Signed-off-by: Robert Richter <rrichter@amd.com> > > > --- > > > drivers/cxl/core/port.c | 18 ++++++++++++++++-- > > > 1 file changed, 16 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c > > > index d10c3580719b..e21a9c3fe4da 100644 > > > --- a/drivers/cxl/core/port.c > > > +++ b/drivers/cxl/core/port.c > > > @@ -1366,8 +1366,24 @@ int devm_cxl_enumerate_ports(struct cxl_memdev *cxlmd) > > > { > > > struct device *dev = &cxlmd->dev; > > > struct device *iter; > > > + struct cxl_dport *dport; > > > + struct cxl_port *port; > > > int rc; > > > > > > + /* > > > + * Skip intermediate port enumeration in the RCH case, there > > > + * are no ports in between a host bridge and an endpoint. Only > > > + * initialize the EP chain. > > > + */ > > > + if (is_cxl_restricted(cxlmd)) { > > > + port = cxl_mem_find_port(cxlmd, &dport); > > > + if (!port) > > > + return -ENXIO; > > > + rc = cxl_add_ep(dport, &cxlmd->dev); > > > > On second look, this seems problematic. While yes it will be deleted > > when the root CXL port dies, it will not be deleted if the cxl_pci > > driver is reloaded. I will code up a unit test to double check. > > > > I note that cxl_add_ep() for the VH case is skipped for the root CXL > > port, so I do not suspect it is needed here either. Did you add it for a > > specific reason? > > Yes, all endpoint iterators need to be reworked. Also true, the first > endpoint is skipped in the chain. So only intermediate EP structs are > touched by the loops actually. > > In particular, cxl_ep_load() returned NULL for the first lookup if the > ep is missing. We could stop the iteration then. I tried to avoid a > rework here, but maybe it is not too extensive as I expected first.
Hmm, ok, let me get the unit test topology working for this to make sure my assumptions are correct about when an @ep reference is used / needed.
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