Hi, I submitted a patch a while ago and then dropped off the face of the
planet like most people do. In my journey to fix DRM/radeonsi in
user-mode emulation I discovered a few bugs. I don't really have the
time to write the infrastructure to make wrapping DRM IOCTLs remotely
not-ugly, but I do want to get patches in for the last bug I encountered
as it's kinda sneaky.
Currently(as of 6 months ago, and I doubt anyone noticed) mmap2 is
completely broken for it's intended use(mapping pages outside the
address limit). The value of the address input to mmap is clipped to an
abi_ulong(4 bytes of 32 bit platforms afaik?) and because of this the
value in pages when converted to addresses and passed to mmap on the
host is invalid and this breaks radeonsi(and probably any other GPU
driver in linux-user.
I don't really know how to fix this in a sane way so I'm looking for ideas.
Another thing I'm looking for ideas wrt is I'm thinking about is some
form of automagic(opt-in, through a new type) pointer/union translation
in IOCTLs over the guest barrier. Currently it's really ugly to wrap
most of the IOCTLs in DRM and amdgpu because the DRM ioctls frequently
pass pointers to the kernel and because of this I don't feel comfortable
merging my patches(manually translating the struct to the types of the
host sucks and feels like redundant work). On top of that AMDGPU uses a
lot of structs where currently having one type for the call would
corrupt the data in the return union.
Last thing: I never really got any performance benefit out of my
scheduler, but I think that's mostly from bad implementation. Is there
any information on TCG's performance characteristics? Thanks.