On Wed, 19 Jul 2023 14:49:07 -0400 Gregory Price <gregory.pr...@memverge.com> wrote:
> On Wed, Jul 19, 2023 at 09:19:47AM +0100, Jonathan Cameron wrote: > > On Tue, 18 Jul 2023 17:30:57 -0400 > > Gregory Price <gregory.pr...@memverge.com> wrote: > > > > > On Mon, Jul 17, 2023 at 06:16:39PM +0100, Jonathan Cameron wrote: > > > > @@ -397,8 +401,9 @@ struct CXLType3Dev { > > > > AddressSpace hostpmem_as; > > > > CXLComponentState cxl_cstate; > > > > CXLDeviceState cxl_dstate; > > > > - CXLCCI cci; > > > > - > > > > + CXLCCI cci; /* Primary PCI mailbox CCI */ > > > > + CXLCCI oob_mctp_cci; /* Initialized only if targetted */ > > > > + > > > > > > I've been humming and hawing over this on the MHD stuff because I wanted > > > to figure out how to "add a CCI command" to a type-3 device without > > > either having a billion definitions for CCI command sets - or doing > > > something like this. > > > > > > I don't hate this design pattern, I just want to ask whether your > > > intent is to end up with CXLType3Dev hosting many CXLCCI's based on what > > > wrapper types you have. > > > > > > Example: a type-3 device with mctp pass through and the MHD command set > > > > > > CXLType3Dev { > > > ... > > > CXLCCI cci; > > > CXLCCI oob_mctp_cci; > > > CXLCCI mhd_cci; > > > ... > > > } > > > > Yes - that's what I was thinking. In some cases a CCI may be accessed by > > tunneling on a different CCI on the same device as well as the option > > of tunneling to different devices. > > > > So far the set that we'll end up with isn't too large. And if some aren't > > used for a given instantiation that's fine if it keeps the code simple. > > We may end up with other MCTP buses and to keep things consistent each one > > will need it's own target CXLCCI. If we need to rethink and make it dynamic > > to some degree we can look at it later. > > > > Maybe a dangerous suggestion. Right now the CCI's are static: > > static const struct cxl_cmd cxl_cmd_set[256][256] That's defined by the ID space for the commands. There can't be more than that many currently.. > > how difficult might it be to allow these tables to be dynamic instead? > Then we could add an interface like this: > > void cxl_add_cmd_set(CXLCCI *cci, CXLCCI *cmd_set, payload_max) { > copy(cci, cmd_set); > } > > This would enable not just adding sub-components piece-meal, but also if > someone wants to model a real device with custom CCI commands, they can > simply define a CCI set and pass it in via > > cxl_add_cmd_set(&ct3d->cci, my_cmd_set, payload_max); Ok. I'm potentially fine with people adding an interface for this, but only if they plan to also upstream the QEMU emulation of their actual device. > > Which lets the existing /dev/cxl/memN device dispatch those commands, > and makes modeling real devices an easier endeavor. > > Only downside is that this may require changing the command structure to > include a callback type and pointer per cci function. The upside is this > would also allow commands to be written somewhat agnostic to the device > they're being inherited by and allow for device nesting like... > > -device cxl-type3, id=ct3d > -device cxl-mhd, target=ct3d > -device my_vendor_cxl_type3, target=ct3d > etc etc > > otherwise we're probably going to end up with a cxl-type3 -device line > 300 characters long. > > Maybe that's over-generalizing a bit much n.n; I'd look to just inherit from a cxl type 3, like Ira did in the PoC for type 2 support. We can then easily add a path to replace the commands set with whatever anyone wants. I'm not sure we want the command line to be used to configure such a device as it'll both get very complex and prove increasingly hard to test more than a small subset of options. https://lore.kernel.org/all/20230517-rfc-type2-dev-v1-0-6eb2e4709...@intel.com/ Jonathan > > ~Gregory