Messages in this thread | | | Date | Thu, 17 Jan 2008 21:03:17 -0500 | From | "H. Peter Anvin" <> | Subject | Re: [mm patch] i915: fix invalid opcode exception on cpus without clflush |
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Kyle McMartin wrote: > i915_flush_ttm was unconditionally executing a clflush instruction > to (obviously) flush the cache. Instead, check if the cpu supports > clflush, and if not, fall back to calling wbinvd to flush the entire > cache. > > Signed-off-by: Kyle McMartin <kmcmartin@redhat.com> > > --- a/drivers/char/drm/i915_buffer.c > +++ b/drivers/char/drm/i915_buffer.c > @@ -286,7 +286,18 @@ void i915_flush_ttm(struct drm_ttm *ttm) > return; > > DRM_MEMORYBARRIER(); > + > +#ifdef CONFIG_X86_32 > + /* Hopefully nobody has built an x86-64 processor without clflush */ > + if (!cpu_has_clflush) { > + wbinvd(); > + DRM_MEMORYBARRIER(); > + return; > + } > +#endif > + > for (i = ttm->num_pages - 1; i >= 0; i--) > drm_cache_flush_page(drm_ttm_get_page(ttm, i)); > + > DRM_MEMORYBARRIER(); > }
The #ifdef is bogus. If it's required, it should go into asm-x86/required_features.h and then cpu_has_clflush is static; otherwise it's just plain wrong.
-hpa
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