From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xSbF606tRzDqrP for ; Thu, 10 Aug 2017 14:46:17 +1000 (AEST) Message-ID: <1502340360.2563.53.camel@kernel.crashing.org> Subject: Re: [PATCH 02/10] powerpc/xive: guest exploitation of the XIVE interrupt controller From: Benjamin Herrenschmidt To: David Gibson , =?ISO-8859-1?Q?C=E9dric?= Le Goater Cc: linuxppc-dev@lists.ozlabs.org, Michael Ellerman , Paul Mackerras Date: Thu, 10 Aug 2017 14:46:00 +1000 In-Reply-To: <20170810042849.GU13670@umbus.fritz.box> References: <1502182579-990-1-git-send-email-clg@kaod.org> <1502182579-990-3-git-send-email-clg@kaod.org> <20170809035306.GC13670@umbus.fritz.box> <20170810042849.GU13670@umbus.fritz.box> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2017-08-10 at 14:28 +1000, David Gibson wrote: > > Also, will POWER9 always have doorbells? In which case you could > reduce it to 3 options. The problem with doorbells on POWER9 guests is that they may have to trap and be emulated by the hypervisor, since the guest threads on P9 don't have to match the HW threads of the core. Thus it's quite possible that using XIVE for IPIs is actually faster than doorbells in that case. Cheers, Ben.