From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A3CBCDB465 for ; Thu, 19 Oct 2023 07:51:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344897AbjJSHvH (ORCPT ); Thu, 19 Oct 2023 03:51:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54110 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232829AbjJSHvG (ORCPT ); Thu, 19 Oct 2023 03:51:06 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3F217109 for ; Thu, 19 Oct 2023 00:51:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Tj2sfG6o4PVcITUMHLw1E1ngyDfKo6Oj8GiFjy0BgNw=; b=MGwUCsFGHsUm4NlLV//62krFjB xxzTXL7q1nbTETm+09oFZdCY9Yn2LcPZ+/ybOPkIRt3oaCtB2X1rcv4uFs8IFhwJGkI/80lZ9xFZw IPdTLSUPa18/8IokSQZ5sWEbBgRFdPNldOBrMk6bsLDjFmkLgtdeyjWXVlwe5VonYLw8Wn/2GGWjl POg1CQmY3qtF8ec3kT7YGz/dNxWJUK7lIQatOtmtxAbdBxz/yPV8jmJayrFRfKKKue0RV63n38eip N1I16yGqj/UhG8efHYI12PM/yQpAPw4S5C0JzlfAwYYfGN+S7lGtQsNZ/jRrydziVa0ynelt9Y+z6 84BSry3A==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1qtNnr-005qil-7D; Thu, 19 Oct 2023 07:50:47 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id DDC6F300392; Thu, 19 Oct 2023 09:50:46 +0200 (CEST) Date: Thu, 19 Oct 2023 09:50:46 +0200 From: Peter Zijlstra To: Michael Ellerman Cc: Srikar Dronamraju , linuxppc-dev , Christophe Leroy , Nicholas Piggin , Rohan McLure , Valentin Schneider , Josh Poimboeuf , Mark Rutland , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 4/6] powerpc/smp: Disable MC domain for shared processor Message-ID: <20231019075046.GN33217@noisy.programming.kicks-ass.net> 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=us-ascii Content-Disposition: inline In-Reply-To: <87pm1b5ia7.fsf@mail.lhotse> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 19, 2023 at 03:48:48PM +1100, Michael Ellerman wrote: > 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? Some KVM people use vcpu pinning and pass-through topology things, slice-of-hardware or something like that. In that scenario you actively do want this. I'm fairly clueless on when this is_shared_processor() gets to be true, so that might already be dealt with..