WP4.2 of the pf-encode audit, validated on RADV PHOENIX (780M, Mesa 26.0.4) under the Vulkan
validation layers rather than by inspection alone. Three of the five reproduce with the
driver naming the violation; one turned out milder than filed and is recorded as such.
1. `ensure_cpu_rgb` cached the staging image on FORMAT ONLY while sizing it to the SOURCE
frame, and the copy uses the CURRENT frame's extent — so a same-format source-size
increase copied past the allocation. Now keyed on (format, width, height). This is the
memory-safety one: on hardware it was 8 x
VUID-vkCmdCopyBufferToImage-imageSubresource-07971 ("extent.width (512) exceeds
imageSubresource width extent (128)") and `submit` returned Ok every single time, so
nothing upstream could notice. Zero after the fix. Note the trigger for anyone re-testing:
the image is cached PER RING SLOT, so the ring must wrap before a slot sees a larger frame
— two differently-sized submits in a row land on different slots and look fine.
2. The RGB-direct CPU padding loop only ever grows a source into the aligned extent; a source
LARGER than the encode extent panicked on the row `copy_from_slice`. Now refused by name,
matching what the DMA-BUF arms already do, so a bad frame takes the encoder-rebuild path
instead of unwinding out of the encode thread with an index message.
3. AV1 wrote `render_width/height_minus_1` but never set
`render_and_frame_size_different`, and AV1 ignores the render size unless that flag says it
differs — so every mode needing 64x16 alignment presented the padding. libdav1d on the
encoded stream now reports `size 1920x1088 ... render 1920x1080`; before, the flag being
unset meant render defaulted to the coded 1088, i.e. 8 rows of duplicated edge pixels
shipped to the client.
4. `read_slot` read the PERF timestamp pool whenever the pool merely EXISTED, but the
padded-RGB path's CPU-upload arm records its own command buffer and writes no timestamps —
reading an unreset query with WAIT is undefined. Now gated on a per-slot `ts_written`,
because "a pool exists" was being used as proof of "the pool was written". SEVERITY
CORRECTION vs the audit: this is not a hang in practice. It needs PUNKTFUNK_PERF *and*
RGB-direct *and* the non-default PUNKTFUNK_VULKAN_RGB_TRUE_EXTENT=0 *and* an unaligned mode
*and* CPU capture, and RADV then fails the read rather than blocking. Another driver may
block, hence the fix.
5. `reset()` re-arms `first_frame`, which was also what decided whether begin-video-coding
declares the rate-control state. But a reset does not rebuild the session, so the CBR
installed earlier is still current when the next frame opens its coding scope: the
declaration was omitted exactly when it was required. Split into `rc_installed`, which
survives reset. On hardware this was
VUID-vkCmdBeginVideoCodingKHR-pBeginInfo-08253 ("no VkVideoEncodeRateControlInfoKHR ... but
the currently set mode is CBR"); zero after.
Also fixes two pre-existing AV1 spec violations that were firing on EVERY frame of a shipped
path and are not in the audit at all — found only because the validation layers were on, and
confirmed untouched by this branch before being attributed as pre-existing:
`constantQIndex` must be 0 unless rate control is DISABLED (VUID-...-10320; this session is
always CBR, so the driver owns Q), and `pStdPictureInfo->pSegmentation` must be NULL
(VUID-...-10350; it pointed at a zeroed struct, and leaving it unset means the same
"segmentation disabled" while being spec-correct).
Items 1 and 5 keep their reproductions as `#[ignore]`d hardware tests, documented as
meaningful only under `VK_LOADER_LAYERS_ENABLE='*validation*'` since the violations are
invisible to the API's return values.
STILL OPEN, filed not fixed (three more pre-existing validation errors the cleanup exposed):
VUID-VkQueryPoolCreateInfo-pNext-pNext on the AV1 and RGB paths, and 2 x
VUID-VkImageViewCreateInfo-image-08336 (the RGB-direct encode-src view's format features lack
VIDEO_ENCODE_INPUT) — the latter may be a validation-layer gap around the VALVE extension
rather than our bug, and wants real analysis rather than a quick patch.
Verified: canonical Linux gate (docker linux/amd64) fmt + clippy --all-targets at default and
at nvenc,vulkan-encode,pyrowave + both test legs; and on RADV PHOENIX all four `vulkan_smoke*`
tests pass at 256x256 and at 1920x1080 with zero validation errors on the paths touched here.
enricobuehler
bab309017d