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authorAaron Durbin <adurbin@chromium.org>2013-04-03 09:57:53 -0500
committerStefan Reinauer <stefan.reinauer@coreboot.org>2013-04-05 21:57:38 +0200
commit6ccb1abfd4aff94711b9950f75b0eb6758c4f4d1 (patch)
tree905bed897c8be4d401d7b0a3ae43ccbd39c656fa /src
parent0dc775e894a3a7b3539eeeb4210bf8b796062274 (diff)
downloadcoreboot-6ccb1abfd4aff94711b9950f75b0eb6758c4f4d1.tar.xz
mtrr: add rom caching comment about hyperthreads
Explicitly call out the effects of hyperthreads running the MTRR code and its impact on the enablement of ROM caching. Change-Id: I14b8f3fdc112340b8f483f2e554c5680576a8a7c Signed-off-by: Aaron Durbin <adurbin@chromium.org> Reviewed-on: http://review.coreboot.org/3018 Tested-by: build bot (Jenkins) Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net> Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Diffstat (limited to 'src')
-rw-r--r--src/include/cpu/x86/mtrr.h6
1 files changed, 5 insertions, 1 deletions
diff --git a/src/include/cpu/x86/mtrr.h b/src/include/cpu/x86/mtrr.h
index 15a5cad090..38c3f7cd0a 100644
--- a/src/include/cpu/x86/mtrr.h
+++ b/src/include/cpu/x86/mtrr.h
@@ -74,7 +74,11 @@ int x86_mtrr_check(void);
/* ROM caching can be used after variable MTRRs are set up. Beware that
* enabling CONFIG_CACHE_ROM will eat through quite a few MTRRs based on
* one's IO hole size and WRCOMB resources. Be sure to check the console
- * log when enabling CONFIG_CACHE_ROM or adding WRCOMB resources. */
+ * log when enabling CONFIG_CACHE_ROM or adding WRCOMB resources. Beware that
+ * on CPUs with core-scoped MTRR registers such as hyperthreaded CPUs the
+ * rom caching will be disabled if all threads run the MTRR code. Therefore,
+ * one needs to call x86_mtrr_enable_rom_caching() after all threads of the
+ * same core have run the MTRR code. */
#if CONFIG_CACHE_ROM
void x86_mtrr_enable_rom_caching(void);
void x86_mtrr_disable_rom_caching(void);