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Mon, 2 Dec 2024 08:02:04 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id Nu7LFnxpTWd5IAAAD6G6ig (envelope-from ); Mon, 02 Dec 2024 08:02:04 +0000 Date: Mon, 2 Dec 2024 09:02:03 +0100 From: Andreas Herrmann To: Ricardo Neri Cc: x86@kernel.org, Andreas Herrmann , Catalin Marinas , Chen Yu , Len Brown , Radu Rendec , Pierre Gondois , Pu Wen , "Rafael J. Wysocki" , Sudeep Holla , Srinivas Pandruvada , Will Deacon , Zhang Rui , Nikolay Borisov , Huang Ying , Ricardo Neri , linux-kernel@vger.kernel.org Subject: Re: [PATCH v8 1/2] cacheinfo: Allocate memory during CPU hotplug if not done from the primary CPU Message-ID: <20241202080203.GC4089@alberich> References: <20241128002247.26726-1-ricardo.neri-calderon@linux.intel.com> <20241128002247.26726-2-ricardo.neri-calderon@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20241128002247.26726-2-ricardo.neri-calderon@linux.intel.com> X-Rspamd-Queue-Id: E794B1F442 X-Spam-Score: -4.01 X-Rspamd-Action: no action X-Spamd-Result: default: False [-4.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_NOT_FQDN(0.50)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; MISSING_XM_UA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[18]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; RCVD_TLS_ALL(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:email,suse.de:email,suse.de:dkim,intel.com:email,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Level: On Wed, Nov 27, 2024 at 04:22:46PM -0800, Ricardo Neri wrote: > 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. > > Moreover, before determining the validity of the last-level cache info, > ensure that it has been allocated. Simply checking for non-zero > cache_leaves() is not sufficient, as some architectures (e.g., Intel > processors) have non-zero cache_leaves() before allocation. > > Dereferencing NULL cacheinfo can occur in update_per_cpu_data_slice_size(). > This function iterates over all online CPUs. However, a CPU may have come > online recently, but its cacheinfo may not have been allocated yet. > > While here, remove an unnecessary indentation in allocate_cache_info(). > > Reviewed-by: Andreas Herrmann > Reviewed-by: Nikolay Borisov > Reviewed-by: Radu Rendec > Reviewed-by: Sudeep Holla > Tested-by: Andreas Herrmann > Fixes: 6539cffa9495 ("cacheinfo: Add arch specific early level initializer") > Signed-off-by: Ricardo Neri > --- Reviewed-by: Andreas Herrmann -- Regards, Andreas