UBUNTU: SAUCE: cacheinfo: Allocate memory for memory if not done from the primary CPU

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

Commit 5944ce092b ("arch_topology: Build cacheinfo from primary CPU")
adds functionality that architectures can use to optionally allocate and
build cacheinfo early during boot. Commit 6539cffa94 ("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@suse.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen Yu <yu.c.chen@intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Radu Rendec <rrendec@redhat.com>
Cc: Pierre Gondois <Pierre.Gondois@arm.com>
Cc: Pu Wen <puwen@hygon.cn>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: Will Deacon <will@kernel.org>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: stable@vger.kernel.org
Reviewed-by: Radu Rendec <rrendec@redhat.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Fixes: 6539cffa94 ("cacheinfo: Add arch specific early level initializer")
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@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@canonical.com>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

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));