From: Peter Zijlstra <peterz@infradead.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
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>,
Heiko Carstens <hca@linux.ibm.com>,
gor@linux.ibm.com, Alexander Gordeev <agordeev@linux.ibm.com>,
borntraeger@linux.ibm.com, Sven Schnelle <svens@linux.ibm.com>,
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>,
Joerg Roedel <joro@8bytes.org>,
suravee.suthikulpanit@amd.com,
Robin Murphy <robin.murphy@arm.com>,
David Woodhouse <dwmw2@infradead.org>,
Baolu Lu <baolu.lu@linux.intel.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
"David S . Miller" <davem@davemloft.net>,
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,
iommu@lists.linux.dev, Linux-Arch <linux-arch@vger.kernel.org>,
linux-crypto@vger.kernel.org,
Stephen Rothwell <sfr@canb.auug.org.au>,
Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH v3 08/11] slub: Replace cmpxchg_double()
Date: Thu, 25 May 2023 15:10:43 +0200 [thread overview]
Message-ID: <20230525131043.GT83892@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <292934ce-73fa-4077-9051-2ad909828f4a@app.fastmail.com>
On Thu, May 25, 2023 at 12:52:06PM +0200, Arnd Bergmann wrote:
> On Thu, May 25, 2023, at 12:29, Peter Zijlstra wrote:
> > On Wed, May 24, 2023 at 11:32:47AM +0200, Peter Zijlstra wrote:
> >> On Mon, May 15, 2023 at 09:57:07AM +0200, Peter Zijlstra wrote:
> >
> > This then also means I need to look at this_cpu_cmpxchg128 and
> > this_cpu_cmoxchg64 behaviour when we dont have the CPUID feature.
> >
> > Because current verions seem to assume the instruction is present.
>
> As far as I could tell when reviewing your series, this_cpu_cmpxchg64()
> is always available on all architectures. Depending on compile-time
> feature detection this would be either a native instruction that
> is guaranteed to work, or the irq-disabled version. On x86, this
> is handled at runtime with alternative_io().
>
> this_cpu_cmpxchg128() clearly needed the system_has_cmpxchg128()
> check, same as system_has_cmpxchg_double() today.
So, having just dug through all that, on x86:
this_cpu_cmpxchg64() is:
X86_CMPXCHG64=n -> fallback, irrespective of CX8
X86_CMPXCHG64=y -> cmpxchg8b
X86_64 -> cmpxchg
I've changed it to be similar between 32bit and 64bit such that both:
cmpxchg#b when CX#, otherwise this_cpu_cmpxchg#b_emu
next prev parent reply other threads:[~2023-05-25 13:17 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-15 7:56 [PATCH v3 00/11] Introduce cmpxchg128() -- aka. the demise of cmpxchg_double() Peter Zijlstra
2023-05-15 7:57 ` [PATCH v3 01/11] cyrpto/b128ops: Remove struct u128 Peter Zijlstra
2023-05-15 7:57 ` [PATCH v3 02/11] types: Introduce [us]128 Peter Zijlstra
2023-05-15 7:57 ` [PATCH v3 03/11] arch: Introduce arch_{,try_}_cmpxchg128{,_local}() Peter Zijlstra
2023-05-15 7:57 ` [PATCH v3 04/11] instrumentation: Wire up cmpxchg128() Peter Zijlstra
2023-05-15 7:57 ` [PATCH v3 05/11] percpu: Wire up cmpxchg128 Peter Zijlstra
2023-05-25 12:49 ` Peter Zijlstra
2023-05-25 22:59 ` Petr Tesařík
2023-05-15 7:57 ` [PATCH v3 06/11] x86,amd_iommu: Replace cmpxchg_double() Peter Zijlstra
2023-05-15 7:57 ` [PATCH v3 07/11] x86,intel_iommu: " Peter Zijlstra
2023-05-15 7:57 ` [PATCH v3 08/11] slub: " Peter Zijlstra
2023-05-24 9:32 ` Peter Zijlstra
2023-05-24 10:13 ` Vlastimil Babka
2023-05-25 10:29 ` Peter Zijlstra
2023-05-25 10:52 ` Arnd Bergmann
2023-05-25 13:10 ` Peter Zijlstra [this message]
2023-05-30 14:22 ` Peter Zijlstra
2023-05-30 19:32 ` Peter Zijlstra
2023-05-15 7:57 ` [PATCH v3 09/11] mm/slub: Fold slab_update_freelist() Peter Zijlstra
2023-05-24 11:58 ` Vlastimil Babka
2023-05-15 7:57 ` [PATCH v3 10/11] arch: Remove cmpxchg_double Peter Zijlstra
2023-05-15 8:52 ` Heiko Carstens
2023-05-15 7:57 ` [PATCH v3 11/11] s390/cpum_sf: Convert to cmpxchg128() Peter Zijlstra
2023-05-15 9:42 ` [PATCH v3 00/11] Introduce cmpxchg128() -- aka. the demise of cmpxchg_double() Arnd Bergmann
2023-05-24 9:39 ` Peter Zijlstra
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