Claude review: drm/xe/pagefault: Add SRCID to pagefault struct

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

**Correctness: Good.**

The SRCID is extracted from `msg[0]` using `PFD_SRC_ID` which is `GENMASK(10, 3)` — an 8-bit field, so storing it in a `u8` is correct.

The `reserved` field change from `u64` to `u8 reserved[7]` preserves the struct size. The original consumer sub-struct layout was:
- `u64 page_addr` (8) + `u32 asid` (4) + `u8 access_type` (1) + `u8 fault_type_level` (1) + `u8 engine_class` (1) + `u8 engine_instance` (1) + `u64 reserved` (8) = 24 bytes

After the patch:
- Same prefix (16) + `u8 srcid` (1) + `u8 reserved[7]` (7) = 24 bytes

Size is preserved, maintaining the 64-byte struct invariant mentioned in the comment on `struct xe_pagefault`.

**Minor concern:** The `pf` in `xe_guc_pagefault_handler` is stack-allocated and not zero-initialized. The `reserved` bytes in the consumer struct are not explicitly zeroed. While the current consumer side doesn't inspect `reserved`, if a future reader relies on it being zero, this could be a latent issue. The existing code has the same pattern for the old `u64 reserved` though, so this is pre-existing.

The debug print addition is fine — `0x%02x` is appropriate for the u8 srcid value.

No issues with this patch.

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Generated by Claude Code Patch Reviewer