On 10/06/15 15:58, Chris Wilson wrote:
As the clflush operates on cache lines, and we can flush any byte address, in order to flush all bytes given in the range we issue an extra clflush on the last byte to ensure the last cacheline is flushed. We can can the iteration to be over the actual cache lines to avoid this double clflush on the last byte.
Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Imre Deak imre.deak@intel.com
drivers/gpu/drm/drm_cache.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_cache.c b/drivers/gpu/drm/drm_cache.c index 9a62d7a53553..6743ff7dccfa 100644 --- a/drivers/gpu/drm/drm_cache.c +++ b/drivers/gpu/drm/drm_cache.c @@ -130,11 +130,12 @@ drm_clflush_virt_range(void *addr, unsigned long length) { #if defined(CONFIG_X86) if (cpu_has_clflush) {
const int size = boot_cpu_data.x86_clflush_size;addr = (void *)(((unsigned long)addr) & -size);
Should this cast be to uintptr_t? Or intptr_t, as size has somewhat strangely been defined as signed? To complete the mix, x86_clflush_size is 'u16'! So maybe we should write
+ const size_t size = boot_cpu_data.x86_clflush_size; + const size_t mask = ~(size - 1); void *end = addr + length; + addr = (void *)(((uintptr_t)addr) & mask);
mb();
for (; addr < end; addr += boot_cpu_data.x86_clflush_size)
for (; addr < end; addr += size) clflushopt(addr);
clflushopt(end - 1);
.Dave.