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 X-Spam-Level: X-Spam-Status: No, score=-8.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E2897C2D0A3 for ; Mon, 9 Nov 2020 15:06:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9C5E120853 for ; Mon, 9 Nov 2020 15:06:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="i/h47HjY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731865AbgKIPGC (ORCPT ); Mon, 9 Nov 2020 10:06:02 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:32214 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731161AbgKIPFQ (ORCPT ); Mon, 9 Nov 2020 10:05:16 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1604934315; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hQQ4XbiqE85iPIRFWzo/hV4LN32LEkjf6ushyTGemPM=; b=i/h47HjYCiKfYccz5Zy+N4SnazXnOkVeMyVlLqP0HrBrCPWZlqpPf2wR6VINIkUa6rDInu FrR42HG/mwc+wdT54vX/8fj6H/W9jj9QrFwXLMEwlW38kgZa+1snu013ECjBxjj4tSfIfx 58Zn6JkUmcVQISUPBYIpv+TWBaIWt7c= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-59-v8p-37KYNo-v1yHp0uLZIg-1; Mon, 09 Nov 2020 10:05:11 -0500 X-MC-Unique: v8p-37KYNo-v1yHp0uLZIg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 069F26D581; Mon, 9 Nov 2020 15:05:10 +0000 (UTC) Received: from [10.36.114.125] (ovpn-114-125.ams2.redhat.com [10.36.114.125]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9C53C1002C0E; Mon, 9 Nov 2020 15:05:04 +0000 (UTC) Subject: Re: [RFC, v0 1/3] vfio/platform: add support for msi To: Vikas Gupta , Alex Williamson Cc: Cornelia Huck , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Vikram Prakash References: <20201105060257.35269-1-vikas.gupta@broadcom.com> <20201105060257.35269-2-vikas.gupta@broadcom.com> <20201105000806.1df16656@x1.home> From: Auger Eric Message-ID: Date: Mon, 9 Nov 2020 16:05:02 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Vikas, On 11/6/20 3:54 AM, Vikas Gupta wrote: > Hi Alex, > > On Thu, Nov 5, 2020 at 12:38 PM Alex Williamson > wrote: >> >> On Thu, 5 Nov 2020 11:32:55 +0530 >> Vikas Gupta wrote: >> >>> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h >>> index 2f313a238a8f..aab051e8338d 100644 >>> --- a/include/uapi/linux/vfio.h >>> +++ b/include/uapi/linux/vfio.h >>> @@ -203,6 +203,7 @@ struct vfio_device_info { >>> #define VFIO_DEVICE_FLAGS_AP (1 << 5) /* vfio-ap device */ >>> #define VFIO_DEVICE_FLAGS_FSL_MC (1 << 6) /* vfio-fsl-mc device */ >>> #define VFIO_DEVICE_FLAGS_CAPS (1 << 7) /* Info supports caps */ >>> +#define VFIO_DEVICE_FLAGS_MSI (1 << 8) /* Device supports msi */ >>> __u32 num_regions; /* Max region index + 1 */ >>> __u32 num_irqs; /* Max IRQ index + 1 */ >>> __u32 cap_offset; /* Offset within info struct of first cap */ >> >> This doesn't make any sense to me, MSIs are just edge triggered >> interrupts to userspace, so why isn't this fully described via >> VFIO_DEVICE_GET_IRQ_INFO? If we do need something new to describe it, >> this seems incomplete, which indexes are MSI (IRQ_INFO can describe >> that)? We also already support MSI with vfio-pci, so a global flag for >> the device advertising this still seems wrong. Thanks, >> >> Alex >> > Since VFIO platform uses indexes for IRQ numbers so I think MSI(s) > cannot be described using indexes. > In the patch set there is no difference between MSI and normal > interrupt for VFIO_DEVICE_GET_IRQ_INFO. in vfio_platform_irq_init() we first iterate on normal interrupts using get_irq(). Can't we add an MSI index at the end of this list with vdev->irqs[i].count > 1 and set vdev->num_irqs accordingly? Thanks Eric > The patch set adds MSI(s), say as an extension, to the normal > interrupts and handled accordingly. Do you see this is a violation? If > yes, then we`ll think of other possible ways to support MSI for the > platform devices. > Macro VFIO_DEVICE_FLAGS_MSI can be changed to any other name if it > collides with an already supported vfio-pci or if not necessary, we > can remove this flag. > > Thanks, > Vikas >