Claude review: gpu: nova-core: fix stack overflow in GSP memory allocation

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Overall Series Review

Subject: gpu: nova-core: fix stack overflow in GSP memory allocation
Author: Tim Kovalenko via B4 Relay <devnull+tim.kovalenko.proton.me@kernel.org>
Patches: 1
Reviewed: 2026-02-14T07:16:12.245002

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This is a single-patch series (v2) fixing a stack overflow in the nova-core GSP driver. The `PteArray` struct, when instantiated with a large number of entries, was being constructed on the stack before being copied into the DMA buffer. For the command queue path (`Cmdq::new`), `GspMem` contains a `PteArray<512>` (4096 bytes / 8 bytes per u64 = 512 entries), resulting in 4096 bytes of stack-allocated PTEs. The patch eliminates the intermediate stack allocation by computing and writing each PTE value directly into the DMA buffer one at a time.

The approach is sound and the two sites are handled differently due to their different DMA abstractions: the `LogBuffer` path uses `as_slice_mut` to get a mutable byte slice and writes PTEs via `copy_from_slice`, while the `Cmdq` path uses raw pointer arithmetic with `addr_of_mut!` and `field_write` to write individual array elements. Both approaches avoid the stack-allocated intermediate array.

There is one correctness concern worth examining in the `Cmdq::new` path related to using `field_write` (which performs a volatile write) for individual array elements versus the original `dma_write!` macro approach that wrote the entire `PteArray` struct atomically.

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