linux-kernel - Re: [PATCH v2 0/2] Skip offline cores when enabling SMT on PowerPC

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Message-Id: <172355300460.69780.8475775851092917266.b4-ty@ellerman.id.au>
Date: Tue, 13 Aug 2024 22:43:24 +1000
From: Michael Ellerman <patch-notifications@...erman.id.au>
To: Michael Ellerman <mpe@...erman.id.au>, Thomas Gleixner <tglx@...utronix.de>, "Nysal Jan K.A." <nysal@...ux.ibm.com>
Cc: Tyrel Datwyler <tyreld@...ux.ibm.com>, Michal Suchanek <msuchanek@...e.de>, Nicholas Piggin <npiggin@...il.com>, Christophe Leroy <christophe.leroy@...roup.eu>, Peter Zijlstra <peterz@...radead.org>, Stephen Rothwell <sfr@...b.auug.org.au>, Sourabh Jain <sourabhjain@...ux.ibm.com>, Dave Hansen <dave.hansen@...ux.intel.com>, Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, Ard Biesheuvel <ardb@...nel.org>, Eric DeVolder <eric.devolder@...cle.com>, Laurent Dufour <ldufour@...ux.ibm.com>, linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, Naveen N Rao <naveen@...nel.org>
Subject: Re: [PATCH v2 0/2] Skip offline cores when enabling SMT on PowerPC

On Wed, 31 Jul 2024 08:31:11 +0530, Nysal Jan K.A. wrote:
> After the addition of HOTPLUG_SMT support for PowerPC [1] there was a
> regression reported [2] when enabling SMT. On a system with at least
> one offline core, when enabling SMT, the expectation is that no CPUs
> of offline cores are made online.
> 
> On a POWER9 system with 4 cores in SMT4 mode:
> $ ppc64_cpu --info
> Core   0:    0*    1*    2*    3*
> Core   1:    4*    5*    6*    7*
> Core   2:    8*    9*   10*   11*
> Core   3:   12*   13*   14*   15*
> 
> [...]

Applied to powerpc/fixes.

[1/2] cpu/SMT: Enable SMT only if a core is online
      https://git.kernel.org/powerpc/c/6c17ea1f3eaa330d445ac14a9428402ce4e3055e
[2/2] powerpc/topology: Check if a core is online
      https://git.kernel.org/powerpc/c/227bbaabe64b6f9cd98aa051454c1d4a194a8c6a

cheers