Host OpenGL for IRIX programs: hostcall + hostgl - #152
Merged
Merged
Conversation
An IRIX program asks IRIS for something the emulated machine does not have by making an ordinary `syscall` with a number IRIX does not use: 3000-3009 (IRIX's highest in 6.5 is 1234). IRIS answers it in `exec_syscall`, before any exception, and the program resumes at the next instruction; the kernel never runs. On a real machine, or an IRIS built without this, an indirect call to one of these numbers fails with EINVAL (measured on real IRIX), which is how a library finds out it is not running here. The trap answers only user-mode `syscall`s outside a delay slot, and only for a number a service is registered for; everything else goes to IRIX untouched. Results come back the IRIX way (v0, v1, a3), plus one outcome of our own, "need page": IRIS sees the TLB, not IRIX's page tables, so a call that needs a page of the program's memory that is not in the TLB, not paged in, or not yet writable answers ENEEDPAGE with the page. The caller touches it, which makes IRIX fault it in as for any access, and calls again; progress is kept across retries, so a buffer larger than the TLB still gets through. Program memory is read and written through DEBUG translation under the current ASID, user addresses only. iris-hostcall/ holds the numbers, the register protocol, the service registry and a self-test service (3009: ping, byte sum, fill), which is registered whenever the feature is built in. Behind `--features hostcall`, off by default. The first service to use it is host OpenGL, in the next commit. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
IRIX OpenGL programs draw on the host's GPU. They are given a replacement libGL (the iris-guest-tools project, github.com/atomchild411/iris-guest-tools, installed in place of SGI's under the same SONAME) whose entry points encode themselves into a command buffer; the buffer reaches the host in one host call whenever a call needs the host before it returns (a result, memory read or written in place, a swap) or the buffer is full. iris-hostgl replays it on the host's OpenGL: a legacy-profile context per GLX context, a framebuffer object per drawable. SGI extensions the host lacks are done in the fragment stage with shaders. A swap flips the frame on the GPU and presents it: on IMPACT the board composites it into its framebuffer under the window (`ImpactScreen`, `Mgras::composite`); otherwise the pixels go back to the program, which puts them up with XShmPutImage/XPutImage. Program memory is read and written through hostcall's need-page protocol, so buffers larger than the TLB work and nothing in IRIX changes. Both halves of the wire protocol -- this crate's decoder (src/calls.rs) and the guest library's encoders -- are generated by tools/glshim.py from one description, tools/glapi.json, which tools/glapi_from_registry.py builds from the Khronos OpenGL registry (tools/khronos/gl.xml, pinned, Apache-2.0, see its README) plus our annotations of what IRIX 6.5 declares differently. Regenerating from this tree reproduces calls.rs and the published guest encoders byte for byte. A handshake checks the protocol number, so a library and an emulator that disagree refuse each other. The only backend is Apple's CGL: on macOS `--features hostgl` registers the service; elsewhere the crate builds and registers nothing, and the guest library reports that host GL is not available. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Collaborator
|
Can you add a feature-flag opt-in on this instead of just determining by platform? We might be distributing on additional platforms which may have this to cause issues. Also other architectures may not support this hostgl application as easily. |
Owner
|
i will add feature flag in the next commit |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Host-accelerated OpenGL for IRIX programs, as two commits:
program makes an ordinary
syscallnumbered 3000-3009, which IRIX doesnot use; IRIS answers it in
exec_syscallbefore any exception and theprogram carries on at the next instruction. Only user-mode calls outside
a delay slot, and only numbers a service is registered for; everything
else goes to IRIX untouched. On a real machine, or IRIS built without
this, the call fails with EINVAL, which is how a library tells. A
"need page" answer covers memory that is not in the TLB yet: the caller
touches the page, IRIX faults it in as usual, and the call is made again
with its progress kept. Includes a self-test service (3009) and a unit
test that runs a real
syscallthrough the trap.--features hostcall,off by default.
a replacement libGL that encodes GL calls into a command buffer; the
buffer comes over in one host call whenever the host is needed (a
result, memory read or written in place, a swap) and
iris-hostglreplays it on the host's OpenGL. On IMPACT, frames are composited
straight into the framebuffer under their window. Both sides of the wire
format are generated from one description built from the Khronos OpenGL
registry (
gl.xml, pinned, Apache-2.0) plus annotations for what IRIX6.5 declares differently; regenerating reproduces the committed decoder
and the published guest encoders byte for byte.
--features hostgl(implies
hostcall). The only backend is Apple's CGL: on other hoststhe crate builds and registers nothing, and the guest libGL says host GL
is unavailable.
The IRIX side is https://github.com/atomchild411/iris-guest-tools
(BSD-3-Clause):
libGL.so/libgl.soreplacements, the host call trap,tests (
glcheck,gltest,irisgltest,glbench,hostcall_test) andinstall scripts.
Testing
cargo test: iris-hostcall (3), iris-hostgl (26, real CGL contexts onmacOS), lib with
hostgl,ip28,jitv2(1180);cargo checkclean with andwithout the features. The Linux build is checked by reading the
cfgsonly (no Linux target here): everything platform-specific is behind
target_os = "macos", so CI will be the first real Linux build.--features ip28,chd,hostgl,jitv2,tcacheon an M4 Pro: the guest tools built from that repository, run as a
logged-in user on
:0.hostcall_testpasses (ping, sum, fill withhundreds of need-page retries, copy-on-write child, kernel address
refused);
glcheck,irisgltestandglbenchpass with the same framechecksums as our earlier tree;
gr_osview(OpenGL on 6.5.22) draws onthe IMPACT desktop.
pixels" (draw in a window, switch to a pbuffer and back, read the window)
failed 4 times in 27 runs today, with the guest library from this
repository and with our earlier one alike.
🤖 Generated with Claude Code