14:22 jbakita: Hello, I'm trying to understand how VRAM PAs are mapped to BAR1 offsets on Fermi and later, but I'm having difficulty digging through the abstractions
14:23 jbakita: Is a separate set of page tables maintained solely for mapping BAR1 offsets to GPU PAs?
14:26 imirkin: you're looking for "instmem" i believe
14:29 jbakita: Yeah, I spent the better part of yesterday digging through various nv50_instobj functions, but I wasn't clear on if/how the BAR1 page tables are connected to the ordinary GPU VA page tables
14:32 imirkin: i'd be lying if i told you i remembered how it worked
14:32 imirkin: my recollection is that it provides an aperture into ... something
14:33 imirkin: look at how the "mapping" logic works on nv50+ ... it's fairly clever unfortunately, a bit hard to trace through
14:42 jbakita: Indeed, I'm at 13 levels of indirection and aliasing thus far from the nvkm_kmap() call to the actual nvkm_vmm_iter() logic which I think does the mapping
14:43 jbakita: Unfortunately, somewhere around level 7 of indirection I lost track of which page tables are being modified and where they're coming from
14:45 imirkin: ;)
14:45 imirkin: yeah, it helps to know the general idea
14:45 imirkin: so
14:45 imirkin: on nv50
14:46 imirkin: wait, you're fermi+ right?
14:46 jbakita: Yeah
14:46 imirkin: ok, on fermi+ ... let's page (ha ha) that in ...
14:46 imirkin: you can have any number of page tables
14:47 imirkin: and there's a pointer to them _somewhere_ ... which indicates the currently active one? wow, i'm way rusty on this
14:47 imirkin: sorry
14:47 imirkin: i do remember working out how imem worked at one point
14:47 imirkin: jbakita: send a question on the mailing list, i'll try to respond to it tonight. or maybe skeggsb_ will have a look, in which case you'll get an actual answer :)
14:48 imirkin: (mailing list = nouveau@lists.freedesktop.org)
14:50 jbakita: Thank you! I'll send an email
14:51 imirkin: i suspect i can sort it out in under half an hour, but i don't have that half-hour right now
14:52 imirkin: (it's easier for me since i'd be re-figuring it out, always easier the 20th time around)
15:09 jbakita: Sent
15:10 jbakita: Oh dear, my message went into moderation though
15:13 jbakita: Is the moderation queue regularly reviewed, or would I be better off joining the list and resending?