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X-CSE-ConnectionGUID: 0VlansqmTJq6IeWiK1jhAQ== X-CSE-MsgGUID: lVLGd1FvRhCymuuKHH6SQw== X-IronPort-AV: E=McAfee;i="6800,10657,11533"; a="69754692" X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="69754692" Received: from orviesa003.jf.intel.com ([10.64.159.143]) by fmvoesa104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 14:36:37 -0700 X-CSE-ConnectionGUID: /uyCc6NjR9KW4BMqoy2VlQ== X-CSE-MsgGUID: 9k1EwDU6QcGQHDVezqm8Xg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="173575364" Received: from gabaabhi-mobl2.amr.corp.intel.com (HELO [10.125.108.229]) ([10.125.108.229]) by ORVIESA003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 14:36:35 -0700 Message-ID: Date: Mon, 25 Aug 2025 14:36:35 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 10/19] x86: LAM compatible non-canonical definition To: Maciej Wieczor-Retman , sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 560FDA0004 X-Stat-Signature: mmgsq9t3sprxqyargnaouneetfb4gwzx X-Rspam-User: X-HE-Tag: 1756157799-786000 X-HE-Meta: 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 oxoa7uqa LbhUWAsF2V7OWGv9xxvShtyaawNYrateqpnQFAJ/tftdly7xJsvMzv6Oxsp1MD3Zz7Lr8P6eOZ93Ms8bUNY8kVp2mT3ZZeZosykthbtF8yYkZMdWCc8b8Or1o95cow7I7pfskoKjRFpAl8KapC4+BXFAf88DYpjQgMZ3HUqp+cgdCJmDVH78Y6Lr0U+1DbODQl5nMqQ+oQ63xmLoMMmSUPV1ZQX3A1BjAvx8qPd5mk6VMWGDlH4O6m7swYDti5vbmMjh/XZDE6C2kDMz97dAvK3V49Q== 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 8/25/25 13:24, Maciej Wieczor-Retman wrote: > +/* > + * CONFIG_KASAN_SW_TAGS requires LAM which changes the canonicality checks. > + */ > +#ifdef CONFIG_KASAN_SW_TAGS > +static __always_inline u64 __canonical_address(u64 vaddr, u8 vaddr_bits) > +{ > + return (vaddr | BIT_ULL(63) | BIT_ULL(vaddr_bits - 1)); > +} > +#else > static __always_inline u64 __canonical_address(u64 vaddr, u8 vaddr_bits) > { > return ((s64)vaddr << (64 - vaddr_bits)) >> (64 - vaddr_bits); > } > +#endif This is the kind of thing that's bound to break. Could we distill it down to something simpler, perhaps? In the end, the canonical enforcement mask is the thing that's changing. So perhaps it should be all common code except for the mask definition: #ifdef CONFIG_KASAN_SW_TAGS #define CANONICAL_MASK(vaddr_bits) (BIT_ULL(63) | BIT_ULL(vaddr_bits-1)) #else #define CANONICAL_MASK(vaddr_bits) GENMASK_UL(63, vaddr_bits) #endif (modulo off-by-one bugs ;) Then the canonical check itself becomes something like: unsigned long cmask = CANONICAL_MASK(vaddr_bits); return (vaddr & mask) == mask; That, to me, is the most straightforward way to do it. I don't see it addressed in the cover letter, but what happens when a CONFIG_KASAN_SW_TAGS=y kernel is booted on non-LAM hardware?