x86: use default cache size if it cannot be determined [BZ #28784]
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| dj/TryBot-apply_patch |
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Patch applied to master at the time it was sent
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| dj/TryBot-32bit |
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Build for i686
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Commit Message
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 2d651eb9265d ("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 2d651eb9265d
---
sysdeps/x86/cacheinfo.h | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
Comments
On Sat, Jan 15, 2022 at 2:13 AM Aurelien Jarno <aurelien@aurel32.net> wrote:
>
> 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 2d651eb9265d ("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 2d651eb9265d
> ---
> sysdeps/x86/cacheinfo.h | 14 ++++++++++----
> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/sysdeps/x86/cacheinfo.h b/sysdeps/x86/cacheinfo.h
> index 4f91a1e98d..65132a9d19 100644
> --- a/sysdeps/x86/cacheinfo.h
> +++ b/sysdeps/x86/cacheinfo.h
> @@ -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;
> --
> 2.34.1
>
LGTM.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Thanks.
@@ -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;