From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e06smtp10.uk.ibm.com (e06smtp10.uk.ibm.com [195.75.94.106]) (using TLSv1.2 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 26F171A0634 for ; Tue, 23 Feb 2016 01:47:15 +1100 (AEDT) Received: from localhost by e06smtp10.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 22 Feb 2016 14:47:12 -0000 Received: from b06cxnps4076.portsmouth.uk.ibm.com (d06relay13.portsmouth.uk.ibm.com [9.149.109.198]) by d06dlp02.portsmouth.uk.ibm.com (Postfix) with ESMTP id 1E037219005C for ; Mon, 22 Feb 2016 14:46:39 +0000 (GMT) Received: from d06av01.portsmouth.uk.ibm.com (d06av01.portsmouth.uk.ibm.com [9.149.37.212]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u1MEksXj44761124 for ; Mon, 22 Feb 2016 14:46:54 GMT Received: from d06av01.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av01.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u1MEkrAj009146 for ; Mon, 22 Feb 2016 07:46:54 -0700 Subject: Re: Fwd: [PATCH v4 08/18] cxl: IRQ allocation for guests To: manoj@linux.vnet.ibm.com References: <1455658751-16970-9-git-send-email-fbarrat@linux.vnet.ibm.com> <56CA2CB1.5030105@linux.vnet.ibm.com> <56CA3A6F.9060402@linux.vnet.ibm.com> Cc: Ian Munsie , michael.neuling@au1.ibm.com, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org From: Frederic Barrat Message-ID: <56CB1F5C.9000608@linux.vnet.ibm.com> Date: Mon, 22 Feb 2016 15:46:52 +0100 MIME-Version: 1.0 In-Reply-To: <56CA3A6F.9060402@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Le 21/02/2016 23:30, Manoj Kumar a écrit : >> Subject: [PATCH v4 08/18] cxl: IRQ allocation for guests >> Date: Tue, 16 Feb 2016 22:39:01 +0100 >> From: Frederic Barrat >> To: imunsie@au1.ibm.com, michael.neuling@au1.ibm.com, >> mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org >> >> The PSL interrupt is not going to be multiplexed in a guest, so an >> interrupt will be allocated for it for each context. > > Not clear why this is the case. Why cannot the CXL later still > multiplex this in a guest? Is this a design choice, an > architectural issue, or the complexity of implementation did > not warrant this? From an API perspective it would have been > preferable to not cascade this change down to all consumers, > and have consumers aware whether they are working in a > bare-metal or a guest environment. It was a design choice made by pHyp. We cannot multiplex the PSL interrupt with the current pHyp implementation. But it doesn't affect the API: the behavior of the API specifying the number of interrupts for a context is consistent: the driver always expects the number of AFU interrupts on bare-metal and in a LPAR. The PSL interrupt is never included. You can see a difference in the maximum number of attachable contexts between bare-metal and powerVM (if the limiting factor is the number of available interrupts). But there's no guarantee for that at the API level. Fred