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x86: use default cache size if it cannot be determined [BZ #28784] 

In some cases (e.g QEMU, non-Intel/AMD CPU) the cache information can
not be retrieved and the corresponding values are set to 0.

Commit 2d651eb926 ("x86: Move x86 processor cache info to
cpu_features") changed the behaviour in such case by defining the
__x86_shared_cache_size and __x86_data_cache_size variables to 0 instead
of using the default values. This cause an issue with the i686 SSE2
optimized bzero/routine which assumes that the cache size is at least
128 bytes, and otherwise tries to zero/set the whole address space minus
128 bytes.

Fix that by restoring the original code to only update
__x86_shared_cache_size and __x86_data_cache_size variables if the
corresponding cache sizes are not zero.

Fixes bug 28784
Fixes commit 2d651eb926

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
This commit is contained in:
Aurelien Jarno 2022-01-17 19:41:40 +01:00
parent 9702a41cee
commit c242fcce06
1 changed files with 10 additions and 4 deletions
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14
sysdeps/x86/cacheinfo.h
View File

@ -61,14 +61,20 @@ init_cacheinfo (void)
long int data = cpu_features->data_cache_size;
/* Round data cache size to multiple of 256 bytes. */
data = data & ~255L;
__x86_data_cache_size_half = data / 2;
__x86_data_cache_size = data;
if (data > 0)
{
__x86_data_cache_size_half = data / 2;
__x86_data_cache_size = data;
}
long int shared = cpu_features->shared_cache_size;
/* Round shared cache size to multiple of 256 bytes. */
shared = shared & ~255L;
__x86_shared_cache_size_half = shared / 2;
__x86_shared_cache_size = shared;
if (shared > 0)
{
__x86_shared_cache_size_half = shared / 2;
__x86_shared_cache_size = shared;
}
__x86_shared_non_temporal_threshold
= cpu_features->non_temporal_threshold;