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From c242fcce06e3102ca663b2f992611d0bda4f2668 Mon Sep 17 00:00:00 2001
From: Aurelien Jarno <aurelien@aurel32.net>
Date: Mon, 17 Jan 2022 19:41:40 +0100
Subject: [PATCH] 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 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
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
---
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;
--
2.27.0
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