From: "Arnd Bergmann" <arnd@arndb.de>
To: "Peter Zijlstra" <peterz@infradead.org>,
"Linus Torvalds" <torvalds@linux-foundation.org>
Cc: "Jonathan Corbet" <corbet@lwn.net>,
"Will Deacon" <will@kernel.org>,
"Boqun Feng" <boqun.feng@gmail.com>,
"Mark Rutland" <mark.rutland@arm.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
dennis@kernel.org, "Tejun Heo" <tj@kernel.org>,
"Christoph Lameter" <cl@linux.com>,
hca@linux.ibm.com, gor@linux.ibm.com,
"Alexander Gordeev" <agordeev@linux.ibm.com>,
borntraeger@linux.ibm.com, svens@linux.ibm.com,
"Herbert Xu" <herbert@gondor.apana.org.au>,
"David S . Miller" <davem@davemloft.net>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
joro@8bytes.org, suravee.suthikulpanit@amd.com,
"Robin Murphy" <robin.murphy@arm.com>,
dwmw2@infradead.org, baolu.lu@linux.intel.com,
"Pekka Enberg" <penberg@kernel.org>,
"David Rientjes" <rientjes@google.com>,
"Joonsoo Kim" <iamjoonsoo.kim@lge.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Roman Gushchin" <roman.gushchin@linux.dev>,
"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 <linux-arch@vger.kernel.org>
Subject: Re: [RFC][PATCH 07/12] percpu: Wire up cmpxchg128
Date: Thu, 29 Dec 2022 14:36:32 +0100 [thread overview]
Message-ID: <1d88ba9f-5541-4b67-9cc8-a361eef36547@app.fastmail.com> (raw)
In-Reply-To: <20221219154119.286760562@infradead.org>
On Mon, Dec 19, 2022, at 16:35, Peter Zijlstra wrote:
> In order to replace cmpxchg_double() with the newly minted
> cmpxchg128() family of functions, wire it up in this_cpu_cmpxchg().
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Does this work on x86 chips without X86_FEATURE_CX16?
As far as I can tell, the new percpu_cmpxchg128_op uses
the cmpxchg16b instruction unconditionally without checking
for the feature bit first, and is now used by this_cpu_cmpxchg()
unconditionally as well.
This is fine for the moment if the only user is mm/slub.c
and that retains the system_has_cmpxchg128() runtime check,
but I think a better interface would be to guarantee that
this_cpu_cmpxchg() always ends up either in a working
inline asm or the generic fallback but not an invalid
opcode.
For consistency, I would also suggest this_cpu_cmpxchg() to
take the same argument types as cmpxchg(): at most 'unsigned
long' sized, with additional this_cpu_cmpxchg64() and
this_cpu_cmpxchg128() macros that take fixed-size arguments.
I have an older patch set that additionally converts all
8-bit and 16-bit cmpxchg()/xchg() calls to cmpxchg_8()/
xchg_8()/cmpxchg_16()/xchg_16() and and leaves only the
fixed-32bit and variable typed 'unsigned long' sized
callers for the weakly typed variant.
Arnd
next prev parent reply other threads:[~2022-12-29 13:40 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-19 15:35 [RFC][PATCH 00/12] Introduce cmpxchg128() -- aka. the demise of cmpxchg_double() Peter Zijlstra
2022-12-19 15:35 ` [RFC][PATCH 01/12] crypto: Remove u128 usage Peter Zijlstra
2022-12-19 15:56 ` Jason A. Donenfeld
2022-12-19 17:00 ` Peter Zijlstra
2022-12-19 17:03 ` Jason A. Donenfeld
2022-12-20 3:50 ` Herbert Xu
2022-12-20 4:11 ` H. Peter Anvin
2022-12-20 4:15 ` Herbert Xu
2022-12-19 15:35 ` [RFC][PATCH 02/12] crypto/ghash-clmulni: Use (struct) be128 Peter Zijlstra
2022-12-20 5:45 ` Eric Biggers
2022-12-19 15:35 ` [RFC][PATCH 03/12] cyrpto/b128ops: Remove struct u128 Peter Zijlstra
2022-12-20 5:52 ` Eric Biggers
2022-12-19 15:35 ` [RFC][PATCH 04/12] types: Introduce [us]128 Peter Zijlstra
2022-12-29 8:30 ` Pavel Machek
2022-12-19 15:35 ` [RFC][PATCH 05/12] arch: Introduce arch_{,try_}_cmpxchg128{,_local}() Peter Zijlstra
2022-12-19 20:07 ` Boqun Feng
2022-12-20 11:08 ` Peter Zijlstra
2022-12-20 14:31 ` Linus Torvalds
2022-12-20 15:09 ` Peter Zijlstra
2023-01-03 13:25 ` Mark Rutland
2023-01-03 14:03 ` Mark Rutland
2023-01-03 16:19 ` Mark Rutland
2023-01-03 16:50 ` Arnd Bergmann
2023-01-04 11:36 ` Mark Rutland
2023-01-04 13:55 ` Mark Rutland
2022-12-22 1:25 ` Boqun Feng
2022-12-22 13:16 ` Peter Zijlstra
2023-01-03 17:12 ` Heiko Carstens
2023-01-09 18:50 ` Mark Rutland
2023-01-12 10:35 ` Peter Zijlstra
2022-12-19 15:35 ` [RFC][PATCH 06/12] instrumentation: Wire up cmpxchg128() Peter Zijlstra
2022-12-19 15:35 ` [RFC][PATCH 07/12] percpu: Wire up cmpxchg128 Peter Zijlstra
2022-12-29 13:36 ` Arnd Bergmann [this message]
2023-01-04 12:09 ` Heiko Carstens
2023-01-09 16:29 ` Peter Zijlstra
2022-12-19 15:35 ` [RFC][PATCH 08/12] s390: Replace cmpxchg_double() with cmpxchg128() Peter Zijlstra
2023-01-10 7:23 ` Heiko Carstens
2023-01-10 8:32 ` Peter Zijlstra
2023-01-10 11:27 ` Mark Rutland
2023-01-10 11:46 ` Heiko Carstens
2023-01-12 11:12 ` Alexander Gordeev
2022-12-19 15:35 ` [RFC][PATCH 09/12] x86,amd_iommu: Replace cmpxchg_double() Peter Zijlstra
2022-12-19 16:47 ` Niklas Schnelle
2022-12-28 8:40 ` Vasant Hegde
2022-12-19 15:35 ` [RFC][PATCH 10/12] x86,intel_iommu: " Peter Zijlstra
2022-12-19 15:35 ` [RFC][PATCH 11/12] slub: " Peter Zijlstra
2023-01-03 15:58 ` Vlastimil Babka
2023-01-03 17:16 ` Heiko Carstens
2023-01-03 19:08 ` Linus Torvalds
2023-01-04 12:07 ` Heiko Carstens
2023-01-09 16:28 ` Peter Zijlstra
2023-01-09 22:02 ` Linus Torvalds
2023-01-09 22:22 ` H. Peter Anvin
2023-01-10 2:09 ` H. Peter Anvin
2023-01-10 10:28 ` Peter Zijlstra
2022-12-19 15:35 ` [RFC][PATCH 12/12] arch: Remove cmpxchg_double Peter Zijlstra
2022-12-22 1:21 ` [RFC][PATCH 00/12] Introduce cmpxchg128() -- aka. the demise of cmpxchg_double() Boqun Feng
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