[PATCH 2/4][Noble] UBUNTU: SAUCE: cacheinfo: Allocate memory for memory if not done from the primary CPU

[You-Sheng Yang]

From: Ricardo Neri <ricardo.neri-calderon at linux.intel.com>

BugLink: https://bugs.launchpad.net/bugs/2049793

Commit 5944ce092b97 ("arch_topology: Build cacheinfo from primary CPU")
adds functionality that architectures can use to optionally allocate and
build cacheinfo early during boot. Commit 6539cffa9495 ("cacheinfo: Add
arch specific early level initializer") lets secondary CPUs correct (and
reallocate memory) cacheinfo data if needed.

If the early build functionality is not used and cacheinfo does not need
correction, memory for cacheinfo is never allocated. x86 does not use the
early build functionality. Consequently, during the cacheinfo CPU hotplug
callback, last_level_cache_is_valid() attempts to dereference a NULL
pointer:

     BUG: kernel NULL pointer dereference, address: 0000000000000100
     #PF: supervisor read access in kernel mode
     #PF: error_code(0x0000) - not present page
     PGD 0 P4D 0
     Oops: 0000 [#1] PREEPMT SMP NOPTI
     CPU: 0 PID 19 Comm: cpuhp/0 Not tainted 6.4.0-rc2 #1
     RIP: 0010: last_level_cache_is_valid+0x95/0xe0a

Allocate memory for cacheinfo during the cacheinfo CPU hotplug callback if
not done earlier.

Cc: Andreas Herrmann <aherrmann at suse.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Chen Yu <yu.c.chen at intel.com>
Cc: Huang Ying <ying.huang at intel.com>
Cc: Len Brown <len.brown at intel.com>
Cc: Radu Rendec <rrendec at redhat.com>
Cc: Pierre Gondois <Pierre.Gondois at arm.com>
Cc: Pu Wen <puwen at hygon.cn>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki at intel.com>
Cc: Sudeep Holla <sudeep.holla at arm.com>
Cc: Srinivas Pandruvada <srinivas.pandruvada at linux.intel.com>
Cc: Will Deacon <will at kernel.org>
Cc: Zhang Rui <rui.zhang at intel.com>
Cc: linux-arm-kernel at lists.infradead.org
Cc: stable at vger.kernel.org
Reviewed-by: Radu Rendec <rrendec at redhat.com>
Reviewed-by: Sudeep Holla <sudeep.holla at arm.com>
Fixes: 6539cffa9495 ("cacheinfo: Add arch specific early level initializer")
Signed-off-by: Ricardo Neri <ricardo.neri-calderon at linux.intel.com>
(cherry-picked from https://lore.kernel.org/all/20231212222519.12834-3-ricardo.neri-calderon@linux.intel.com/raw)
Signed-off-by: You-Sheng Yang <vicamo.yang at canonical.com>
---
 drivers/base/cacheinfo.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index 967c5cf3fb1d6..735ccead190ec 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -557,7 +557,11 @@ static inline int init_level_allocate_ci(unsigned int cpu)
 	 */
 	ci_cacheinfo(cpu)->early_ci_levels = false;
 
-	if (cache_leaves(cpu) <= early_leaves)
+	/*
+	 * Some architectures (e.g., x86) do not use early initialization.
+	 * Allocate memory now in such case.
+	 */
+	if (cache_leaves(cpu) <= early_leaves && per_cpu_cacheinfo(cpu))
 		return 0;
 
 	kfree(per_cpu_cacheinfo(cpu));
-- 
2.43.0