DXMT: backport dynamic CPU encoding heap#766
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Backport upstream DXMT commit 998714300fe1144114fd689ce1f7c36be6c58189. The vendored DXMT 0.60 encoder used a single fixed CPU encoding heap and only logged when the heap overflowed, then returned memory past the allocation. Upstream DXMT fixed this by switching to dynamically managed encoding heap chunks and retiring underused chunks after repeated non-use. Origin: 3Shain/dxmt@9987143 Signed-off-by: Ronnie Nibali <rnibali@gmail.com>
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DXMT v0.80 audit update: This is already addressed by newer DXMT. The dynamic CPU encoding heap work landed upstream before v0.80, so updating the vendored DXMT tree to v0.80 would include the equivalent fix. So this PR is best understood as a narrow backport for VirtualBox's currently vendored DXMT snapshot. |
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Summary
Backport upstream DXMT commit
998714300fe1144114fd689ce1f7c36be6c58189,feat(dxmt): dynamically grow & shrink cpu encoding buffer.VirtualBox vendors DXMT 0.60 in
src/libs/dxmt-0.60. In that version,ArgumentEncodingContext::allocate_cpu_heap()logscpu argument heap overflow, expect error.when a command chunk exceeds the fixed CPU encoding heap, but then still returns a pointer past the backing allocation.The upstream DXMT fix replaces the single fixed heap with dynamically managed CPU encoding heap chunks and retires underused chunks after repeated non-use. The fix is included upstream starting with DXMT
v0.71; current DXMT is newer than the vendored0.60snapshot.Why
A local Windows 11 Arm guest stress test on a macOS/Arm host hit repeated DXMT CPU encoding heap overflows, followed by Metal command-buffer out-of-memory errors and a broken guest display update path. Since DXMT already fixed the allocator upstream, this PR intentionally backports the upstream change rather than introducing a VirtualBox-specific rewrite.
A full DXMT
v0.60 -> v0.80refresh is much larger than this specific crash fix, so this keeps the change narrow and attributable.Validation
src/libs/dxmt-0.60paths.kmk VBoxDxMt VBOX_LLVM_PATH=/opt/homebrew/opt/llvm@15 VBOX_LLVM_CONFIG=/opt/homebrew/opt/llvm@15/bin/llvm-config ...VBoxDxMt.dylib.Closes #765.