Re: [mm patch] i915: fix invalid opcode exception on cpus withoutclflush
From: H. Peter Anvin
Date: Thu Jan 17 2008 - 21:14:15 EST
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@xxxxxxxxxx>
--- 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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