Claude review: drm/vmwgfx: Fix hrtimer interrupt storm due to 0-period vblank

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Overall Series Review

Subject: drm/vmwgfx: Fix hrtimer interrupt storm due to 0-period vblank
Author: w15303746062@163.com
Patches: 3
Reviewed: 2026-05-25T18:01:51.532748

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This is a v1→v2 iteration of a single patch fixing a real DoS vulnerability: userspace can craft a display mode with huge `crtc_clock` and tiny `htotal*vtotal`, causing `drm_calc_timestamping_constants()` to truncate `framedur_ns` to 0. This leads to an infinite hrtimer hard-IRQ loop that locks up the CPU.

The v2 correctly moves the fix from the vmwgfx driver into the DRM core (`drm_crtc_vblank_start_timer()`), which is the right location — the timer setup logic was refactored into the core, so the fix there protects all drivers using software vblank simulation, not just vmwgfx. The v2 also correctly drops `WARN_ON_ONCE()` to avoid `panic_on_warn` issues from unprivileged userspace.

The fix is a reasonable defensive bandaid. A more thorough long-term fix would reject these pathological modes earlier in the pipeline (e.g., in `atomic_check` or mode validation), but as a targeted DoS prevention this is appropriate for stable backport.

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