From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3zSxSZ2n8RzDqpw for ; Sat, 27 Jan 2018 11:27:58 +1100 (AEDT) Received: from ozlabs.org (bilbo.ozlabs.org [103.22.144.67]) by bilbo.ozlabs.org (Postfix) with ESMTP id 3zSxSZ1DcMz8sxQ for ; Sat, 27 Jan 2018 11:27:58 +1100 (AEDT) Date: Sat, 27 Jan 2018 10:27:35 +1000 From: Nicholas Piggin To: Paul Mackerras Cc: linuxppc-dev@ozlabs.org Subject: Re: [RFC PATCH] powerpc/powernv: Provide a way to force a core into SMT4 mode Message-ID: <20180127102735.5075a560@roar.ozlabs.ibm.com> In-Reply-To: <20180125050512.GA18744@fergus.ozlabs.ibm.com> References: <20180125050512.GA18744@fergus.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 25 Jan 2018 16:05:12 +1100 Paul Mackerras wrote: > POWER9 processors up to and including "Nimbus" v2.2 have hardware > bugs relating to transactional memory and thread reconfiguration. > One of these bugs has a workaround which is to get the core into > SMT4 state temporarily. This workaround is only needed when > running bare-metal. How often will this be triggered, in practice? If it's infrequent, then would it be better to just do a smp_call_function on siblings and get them all spinning there? I'm looking sadly at the added sync... Thanks, Nick