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charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 53F43180007 X-Stat-Signature: uqgktruxstioedjqujn35i1kgonhtxpc X-Rspam-User: X-HE-Tag: 1755279901-476262 X-HE-Meta: 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 uDgLoNrv 6LitJIZjRJOisrSDrjh41X0HGBeHAQ6xDa4CLRFfW20gWOGwjt0Lj9ZoDbdPu7PRqkKVLveVDYaNmyPKp7Wc9j8N2YYCLFjPiGxwv93beYfZvVldTBaE40oErG5TP8i9GSufJDO/n+0RNiSErovHGJ2AY4U+OXOAOZ/krNf/wLSfBzIUMuAjSk7Fju1H8dM1lL1IOqtzLXunfRyTzA8w3UddrcbewBhZC4+5ZzkzWwqqdquX8hgIK+BqjhmKJS9v60bZ6ZGeR5z457g62HjRpSbQIA1OaYf+MXwyYnG6W6GrAPHo50b3YivK+7JZvM67JhZb/HJZr/Gt3qd18+hHIVS1JYo7udfTYg3wLZYFkbwfh5mqBv8i8r8V1gqDtIXPDwEyP/uFIgIfJz0b2C0zx7yA5fND5RNhMG2ec6Jxd/9uLVsi2QqHHpPSlVAutGGF+vLmhJ+5UOszvxdg= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Aug 15, 2025 at 04:10:59PM +0100, Yeoreum Yun wrote: > > > Like we do in mte_enable_kernel_asymm(), if the feature is not available > > > just fall back to checking both reads and writes in the chosen > > > async/sync/asymm way. You can add some pr_info() to inform the user of > > > the chosen kasan mode. It's really mostly an performance choice. > > > > But MTE_STORE_ONLY is defined as a SYSTEM_FEATURE. > > This means that when it is called from kasan_init_hw_tags_cpu(), > > the store_only mode is never set in system_capability, > > so it cannot be checked using cpus_have_cap(). > > > > Although the MTE_STORE_ONLY capability is verified by > > directly reading the ID register (seems ugly), > > my concern is the potential for an inconsistent state across CPUs. > > > > For example, in the case of ASYMM, which is a BOOT_CPU_FEATURE, > > all CPUs operate in the same mode — > > if ASYMM is not supported, either > > all CPUs run in synchronous mode, or all run in asymmetric mode. > > > > However, for MTE_STORE_ONLY, CPUs that support the feature will run in store-only mode, > > while those that do not will run with full checking for all operations. > > > > If we want to enable MTE_STORE_ONLY in kasan_init_hw_tags_cpu(), > > I believe it should be reclassified as a BOOT_CPU_FEATURE.x > > Otherwise, the cpu_enable_mte_store_only() function should still be called > > as the enable callback for the MTE_STORE_ONLY feature. > > In that case, kasan_enable_store_only() should be invoked (remove late init), > > and if it returns an error, stop_machine() should be called to disable > > the STORE_ONLY feature on all other CPUs > > if any CPU is found to lack support for MTE_STORE_ONLY. > > > > Am I missing something? Good point. > So, IMHO like the ASYMM feature, it would be good to change > MTE_STORE_ONLY as BOOT_CPU_FEATURE. > That would makes everything as easiler and clear. Yeah, let's do this. If people mix different features, we'll revisit at that time. The asymmetric tag checking is also a boot CPU feature. -- Catalin