Patch "cacheinfo: Check sib_leaf in cache_leaves_are_shared()" has been added to the 6.2-stable tree

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This is a note to let you know that I've just added the patch titled

    cacheinfo: Check sib_leaf in cache_leaves_are_shared()

to the 6.2-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     cacheinfo-check-sib_leaf-in-cache_leaves_are_shared.patch
and it can be found in the queue-6.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 9ef377191040383c36ccde353a88519a9cb26f5e
Author: Pierre Gondois <pierre.gondois@xxxxxxx>
Date:   Fri Apr 14 10:14:49 2023 +0200

    cacheinfo: Check sib_leaf in cache_leaves_are_shared()
    
    [ Upstream commit 7a306e3eabf2b2fd8cffa69b87b32dbf814d79ce ]
    
    If there is no ACPI/DT information, it is assumed that L1 caches
    are private and L2 (and higher) caches are shared. A cache is
    'shared' between two CPUs if it is accessible from these two
    CPUs.
    
    Each CPU owns a representation (i.e. has a dedicated cacheinfo struct)
    of the caches it has access to. cache_leaves_are_shared() tries to
    identify whether two representations are designating the same actual
    cache.
    
    In cache_leaves_are_shared(), if 'this_leaf' is a L2 cache (or higher)
    and 'sib_leaf' is a L1 cache, the caches are detected as shared as
    only this_leaf's cache level is checked.
    This is leads to setting sib_leaf as being shared with another CPU,
    which is incorrect as this is a L1 cache.
    
    Check 'sib_leaf->level'. Also update the comment as the function is
    called when populating 'shared_cpu_map'.
    
    Fixes: f16d1becf96f ("cacheinfo: Use cache identifiers to check if the caches are shared if available")
    Signed-off-by: Pierre Gondois <pierre.gondois@xxxxxxx>
    Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230414081453.244787-2-pierre.gondois@xxxxxxx
    Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index f05acf3c16c6b..88205a240fb2e 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -38,11 +38,10 @@ static inline bool cache_leaves_are_shared(struct cacheinfo *this_leaf,
 {
 	/*
 	 * For non DT/ACPI systems, assume unique level 1 caches,
-	 * system-wide shared caches for all other levels. This will be used
-	 * only if arch specific code has not populated shared_cpu_map
+	 * system-wide shared caches for all other levels.
 	 */
 	if (!(IS_ENABLED(CONFIG_OF) || IS_ENABLED(CONFIG_ACPI)))
-		return !(this_leaf->level == 1);
+		return (this_leaf->level != 1) && (sib_leaf->level != 1);
 
 	if ((sib_leaf->attributes & CACHE_ID) &&
 	    (this_leaf->attributes & CACHE_ID))



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