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Tue, 3 Jan 2023 11:50:21 -0500 (EST) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.7.0-alpha0-1185-g841157300a-fm-20221208.002-g84115730 Mime-Version: 1.0 Message-Id: <8fea3494-1d1f-4f64-b525-279152cf430b@app.fastmail.com> In-Reply-To: References: <20221219153525.632521981@infradead.org> <20221219154119.154045458@infradead.org> Date: Tue, 03 Jan 2023 17:50:00 +0100 From: "Arnd Bergmann" To: "Mark Rutland" , "Peter Zijlstra" Cc: "Boqun Feng" , "Linus Torvalds" , "Jonathan Corbet" , "Will Deacon" , "Catalin Marinas" , dennis@kernel.org, "Tejun Heo" , "Christoph Lameter" , "Heiko Carstens" , gor@linux.ibm.com, "Alexander Gordeev" , borntraeger@linux.ibm.com, svens@linux.ibm.com, "Herbert Xu" , "David S . Miller" , "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "Dave Hansen" , x86@kernel.org, "H. Peter Anvin" , joro@8bytes.org, suravee.suthikulpanit@amd.com, "Robin Murphy" , dwmw2@infradead.org, baolu.lu@linux.intel.com, "Pekka Enberg" , "David Rientjes" , "Joonsoo Kim" , "Andrew Morton" , "Vlastimil Babka" , "Roman Gushchin" , "Hyeonggon Yoo" <42.hyeyoo@gmail.com>, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, linux-crypto@vger.kernel.org, iommu@lists.linux.dev, Linux-Arch Subject: Re: [RFC][PATCH 05/12] arch: Introduce arch_{,try_}_cmpxchg128{,_local}() Content-Type: text/plain X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: F347B10000D X-Stat-Signature: si6ig8pu36szoatabwy5zx3e3dka15ec X-HE-Tag: 1672764627-247263 X-HE-Meta: U2FsdGVkX19Y7iNNqMZEq56hg96UcAOoP/nQL0eAqlw3ur/05vflu0rvGyuBNrd1akhflpLwomZhHaDWXVGNDLqwsAAOM3RP4GG8LPl+ebOZJ17zLygjdHjJVzwOXxVlJvwxByY9Jk9e/B/PROJG5FvsMVl2SUnOyUql0OSXJmJrG8jAS1wEC/aq4gXR754PhPLEjGCgPduJ3i6N64oynfcDEgOrLdueEF0+2YRJm3wpF9Ngawdbto2cY2M+QV0+zwjEkldePnbpvkrDE4zBb8cksNTOJhOKEDiAJvDwcW7XzCJ4lNVht57nsVheEPGvRDV+Z0sLez1ZIhpbUHkQ4sizhApm1pCb+sS5gnFbxeZYgGRW3a76vYZkU3gCG7RYPGogwyA6LWvCbmNXZ57/sBUHNgw8VdfxHyskZEn5WMv0gaxX7+sj6NcboXlUg1mEErQcpk2TI3XoVZeu/SpIi45nW2KGOJe6xBfXgoJLdTK1vU1d0imF1S/5oY5EmFizNmHtPxYqlQtocFK2CcfObM+h0yzDIsFnOLkbFG70kD+M5T9zhYC0bd3i/t7maf8oLHLmz/Ch7KPOuaWGg4zgGuoQYap5ddcxyJsmE+BZ556kHr4kfPzeAY4bN4A3PKmleFoLnyG5tLkKCi/Oy/TdXcYA+NdXp091cKTVoOTt5IJp+ZWWUomsg9WmJVh9XPU+8hvpVsV2uriek6543EjqpYeR0tzAAjv/Nwp9kuIHmbX2B4fv5JD8QERUljZFT9yZod8AXlGKWFK6uHvpe/KploOgwclqSa1jxMCgIzhENgXaAs09yE8LHbR0F50JWHhlsNblEpreO3K4IEjUi20OWOw3X0kjLP7tL+OGCW+Z+BaWesbXJuAPjV+V2yus76IRjCpyPrmoM37g6j0l7uPspvnCjSjFURm8zKqe4CKp5V/JRHsnYbFktM5BuYhrJ3bXrsZBDMMmWRt6T35U0dI W7Xvm1jt I8GMk0ZGtJSFY0ajSUs8pVzQi762VpJfNVu/bdX7uWfGcMGBVbVTfhf/mxtzGZc63gwH9 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: On Tue, Jan 3, 2023, at 17:19, Mark Rutland wrote: > On Tue, Jan 03, 2023 at 02:03:37PM +0000, Mark Rutland wrote: >> On Tue, Jan 03, 2023 at 01:25:35PM +0000, Mark Rutland wrote: >> > On Tue, Dec 20, 2022 at 12:08:16PM +0100, Peter Zijlstra wrote: >> ... makes GCC much happier: > >> ... I'll go check whether clang is happy with that, and how far back that can >> go, otherwise we'll need to blat the high half with a separate constaint that >> (ideally) doesn't end up allocating a pointless address register. > > Hmm... from the commit history it looks like GCC prior to 5.1 might not be > happy with that, but that *might* just be if we actually do arithmetic on the > value, and we might be ok just using it for memroy effects. I can't currently > get such an old GCC to run on my machines so I haven't been able to check. gcc-5.1 is the oldest (barely) supported compiler, the minimum was last raised from gcc-4.9 in linux-5.15. If only gcc-4.9 and older are affected, we're good on mainline but may still want a fix for stable kernels. I checked that the cross-compiler binaries from [1] still work, but I noticed that this version is missing the native aarch64-to-aarch64 compiler (x86 to aarch64 and vice versa are there), and you need to install libmpfr4 [2] as a dependency. The newer compilers (6.5.0 and up) don't have these problems. Arnd [1] https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/arm64/5.5.0/ [2] http://ftp.uk.debian.org/debian/pool/main/m/mpfr4/libmpfr4_3.1.5-1_arm64.deb