Public bug reported:
Hello Ubuntu graphics package maintainers,
Please review this experimental, AI-assisted robustness proposal for the open
NVIDIA
driver. It is an RFC/wishlist request, not a reproduced hardware defect, a
proven
performance improvement, a new complete driver, or a request for immediate SRU
upload.
Prepared for: Jibin Babu
Target package: nvidia-graphics-drivers-595, 595.84-0ubuntu0.24.04.1
Test environment: Ubuntu 24.04.4 LTS, Linux 6.8.0-139-generic, x86-64,
Intel Raptor Lake-P graphics plus NVIDIA RTX 4060 Laptop GPU; open driver
595.84.
PROPOSAL
Use kvmalloc_array(..., GFP_KERNEL | __GFP_ZERO) for the struct page pointer
array in
nv_drm_lock_user_pages on Linux, and kvfree on both error and release paths.
The current nv_drm_calloc/kzalloc allocation needs physically contiguous
storage even
though this array does not require it. The change permits vmalloc fallback while
retaining zero initialization, overflow checks, and existing pin/unpin
semantics.
The non-Linux branch and generic allocation helpers are unchanged.
TESTS COMPLETED
- All five NVIDIA modules compiled against the installed 6.8.0-139 kernel
headers.
- 2,219 regression scenarios passed in each of three ASan/UBSan harness modes:
baseline Linux, patched Linux, and preserved non-Linux branch (6,657 total).
Exact driver functions are extracted; kernel APIs are MOCKED.
- Thirty real GEM user-memory import/close operations passed on the UNMODIFIED
loaded driver, over sizes from 4 KiB through 256 MiB; no memory pressure
injected.
- Patch applicability checked against the current upstream main source snapshot.
LIMITATIONS / REVIEW REQUEST
The patched modules have NOT been loaded. No A/B runtime benchmark, actual
kernel
allocation fault injection, power measurement, FPS gain, 8K playback
improvement,
suspend/resume test, or broad hardware/kernel compatibility has been
established.
No real hardware allocation failure was reproduced. The existing-driver baseline
succeeded throughout. Vmalloc fallback has overhead and is not always faster.
Please advise whether this allocation change is appropriate and whether review
should proceed upstream first. An independent kernel review and isolated runtime
validation are necessary before considering packaging or installation.
The attached review material contains tests, source/patch, environment
metadata, and
sanitized logs, without private documents or credentials. This is an
AI-assisted draft;
no contributor agreement or DCO attestation has been signed on the submitter's
behalf.
PATCH (also supplied as a separate attachment)
--- a/kernel-open/nvidia-drm/nvidia-drm-os-interface.c
+++ b/kernel-open/nvidia-drm/nvidia-drm-os-interface.c
@@ -83,7 +83,13 @@
struct page **user_pages;
int pages_pinned;
+#if defined(NV_LINUX)
+ /* The page-pointer array need not be physically contiguous. */
+ user_pages = kvmalloc_array(pages_count, sizeof(*user_pages),
+ GFP_KERNEL | __GFP_ZERO);
+#else
user_pages = nv_drm_calloc(pages_count, sizeof(*user_pages));
+#endif
if (user_pages == NULL) {
return -ENOMEM;
@@ -113,7 +119,11 @@
}
}
+#if defined(NV_LINUX)
+ kvfree(user_pages);
+#else
nv_drm_free(user_pages);
+#endif
return (pages_pinned < 0) ? pages_pinned : -EINVAL;
}
@@ -127,7 +137,11 @@
NV_UNPIN_USER_PAGE(pages[i]);
}
+#if defined(NV_LINUX)
+ kvfree(pages);
+#else
nv_drm_free(pages);
+#endif
}
/*
** Affects: nvidia-graphics-drivers-595 (Ubuntu)
Importance: Undecided
Status: New
** Tags: nvidia-drm patch wishlist
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https://bugs.launchpad.net/bugs/2166578
Title:
[RFC] nvidia-drm: allow vmalloc fallback for user-memory page arrays
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