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Thu, 19 Oct 2023 13:16:59 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0B47820043; Thu, 19 Oct 2023 13:16:59 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9D60320040; Thu, 19 Oct 2023 13:16:56 +0000 (GMT) Received: from linux.vnet.ibm.com (unknown [9.126.150.29]) by smtpav07.fra02v.mail.ibm.com (Postfix) with SMTP; Thu, 19 Oct 2023 13:16:56 +0000 (GMT) Date: Thu, 19 Oct 2023 18:46:55 +0530 From: Srikar Dronamraju To: Michael Ellerman Subject: Re: [PATCH v2 4/6] powerpc/smp: Disable MC domain for shared processor Message-ID: <20231019131655.GJ2194132@linux.vnet.ibm.com> References: <20231018163751.2423181-1-srikar@linux.vnet.ibm.com> <20231018163751.2423181-5-srikar@linux.vnet.ibm.com> <87pm1b5ia7.fsf@mail.lhotse> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <87pm1b5ia7.fsf@mail.lhotse> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: -dcD9fF8egfTbF7mBqOUvkJVRQPDE2J_ X-Proofpoint-GUID: 3bJV3pVYuW0ZlhfUtqPrhT849ube8twE X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.980,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-10-19_11,2023-10-19_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 adultscore=0 impostorscore=0 phishscore=0 priorityscore=1501 mlxlogscore=999 bulkscore=0 malwarescore=0 mlxscore=0 spamscore=0 suspectscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2309180000 definitions=main-2310190114 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Srikar Dronamraju Cc: Mark Rutland , Valentin Schneider , Peter Zijlstra , linux-kernel@vger.kernel.org, Nicholas Piggin , Rohan McLure , linuxppc-dev , Josh Poimboeuf Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" * Michael Ellerman [2023-10-19 15:48:48]: > Srikar Dronamraju writes: > > Like L2-cache info, coregroup information which is used to determine MC > > sched domains is only present on dedicated LPARs. i.e PowerVM doesn't > > export coregroup information for shared processor LPARs. Hence disable > > creating MC domains on shared LPAR Systems. > > > > Signed-off-by: Srikar Dronamraju > > --- > > arch/powerpc/kernel/smp.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c > > index 498c2d51fc20..29da9262cb17 100644 > > --- a/arch/powerpc/kernel/smp.c > > +++ b/arch/powerpc/kernel/smp.c > > @@ -1046,6 +1046,10 @@ static struct cpumask *cpu_coregroup_mask(int cpu) > > > > static bool has_coregroup_support(void) > > { > > + /* Coregroup identification not available on shared systems */ > > + if (is_shared_processor()) > > + return 0; > > That will catch guests running under KVM too right? Do we want that? > Only dedicated LPARS on PowerVM expose coregroup or Hemisphere information. Currently other systems including KVMs don't expose this information to the OS. > > return coregroup_enabled; > > What does coregroup_enabled mean now? > > I'd rather this was actually checking the presence of something, rather > than just hard coding that shared processor means no coregroup support. > On a shared LPAR, the Hypervisors would like to have the flexibility to schedule LPAR on any core within the DIE without having to further think about the Hemisphere locality of the core. > cheers -- Thanks and Regards Srikar Dronamraju