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=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 0001CC433E0 for ; Thu, 6 Aug 2020 17:21:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4EBD223120 for ; Thu, 6 Aug 2020 17:21:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="JpkurE4T" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729392AbgHFRVM (ORCPT ); Thu, 6 Aug 2020 13:21:12 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:53400 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729376AbgHFRVF (ORCPT ); Thu, 6 Aug 2020 13:21:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1596734464; 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: in-reply-to:in-reply-to:references:references; bh=z0yMbsT7pcgi1iAHyYcod+CvrElFV6deSSG6mOjxpA8=; b=JpkurE4TQ0HhBbugzOI7UcoukIohiO+2Q5pZdlZta5wGBQh2pLUmIxq935ZGVMRDOU724r ucCGYCiLwevzBgTcx3OoYOAhWyEp4urAQQBfXgdMC+HUyEiw9BIFqhjKmfxoy6b4WXPCq7 gesZp62tf4JugFPJPFt1yEBtsQy+A7I= Received: from mail-ej1-f72.google.com (mail-ej1-f72.google.com [209.85.218.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-430-UXY6awtINe2hI5AmW3Xsdw-1; Thu, 06 Aug 2020 07:39:12 -0400 X-MC-Unique: UXY6awtINe2hI5AmW3Xsdw-1 Received: by mail-ej1-f72.google.com with SMTP id lg2so13622407ejb.23 for ; Thu, 06 Aug 2020 04:39:12 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=z0yMbsT7pcgi1iAHyYcod+CvrElFV6deSSG6mOjxpA8=; b=QNqNJkPyFAAc+YLamO7ydEFLRpENZjOJbFGCYyn0/+i077yzpdg8+MOgV2VOO7yX1R /RzKbvFwmI05cpjGeLc73sbSCWsQDVsMnDuiPW70ZueTn4ulSOk4kJZOM5+n5Oo5r7fJ MayOJOc2MO3REePgQLjEFEkgwgHACU4G75UFtiY501YbSW8RvZYsD/5igTtkFfWyip9G KTkZEazA/wjogoZ5+81VNCNtVI656ba3/OFqtbOh6GGRjNZmLpT2m+oKf2ipEr/E7R+X TxrhIUWFqy2K/4dZHZ/kCUpzgCYLNmCM1JPfUpgbERFC7FMfr9wOEUw/p7dtWdUPaM/N 2CLg== X-Gm-Message-State: AOAM530a1OQ34t/1GErgOkR+rb6HDcAnFt7XIsA5EbYde+cPpykuMkIk 02OqlrjjXjkaavNFCHRT6ZKRd25bk5BQkNctk3MwjFGtuuGMlTr6FJ/S+YjQ0DbeY1roTk9Much DtOtKjakPjxM6jXGmD1dGITaN X-Received: by 2002:a50:d485:: with SMTP id s5mr3707037edi.285.1596713951113; Thu, 06 Aug 2020 04:39:11 -0700 (PDT) X-Google-Smtp-Source: ABdhPJw9gpH7Y4wZjbEShVJ7bFDHbXcr/x4vdBu+Kk8uS1Zn8NzRbVW/Adp0kk2I0m9EFJ/FFoNX6Q== X-Received: by 2002:a50:d485:: with SMTP id s5mr3707021edi.285.1596713950936; Thu, 06 Aug 2020 04:39:10 -0700 (PDT) Received: from vitty.brq.redhat.com (g-server-2.ign.cz. [91.219.240.2]) by smtp.gmail.com with ESMTPSA id w7sm3521262ejb.3.2020.08.06.04.39.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Aug 2020 04:39:10 -0700 (PDT) From: Vitaly Kuznetsov To: "Michael S. Tsirkin" Cc: kvm@vger.kernel.org, Paolo Bonzini , Sean Christopherson , Wanpeng Li , Jim Mattson , Peter Xu , Julia Suvorova , Andy Lutomirski , linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/3] KVM: x86: KVM_MEM_PCI_HOLE memory In-Reply-To: <20200806055008-mutt-send-email-mst@kernel.org> References: <20200728143741.2718593-1-vkuznets@redhat.com> <20200805201851-mutt-send-email-mst@kernel.org> <873650p1vo.fsf@vitty.brq.redhat.com> <20200806055008-mutt-send-email-mst@kernel.org> Date: Thu, 06 Aug 2020 13:39:09 +0200 Message-ID: <87wo2cngv6.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "Michael S. Tsirkin" writes: > About the feature bit, I am not sure why it's really needed. A single > mmio access is cheaper than two io accesses anyway, right? So it makes > sense for a kvm guest whether host has this feature or not. > We need to be careful and limit to a specific QEMU implementation > to avoid tripping up bugs, but it seems more appropriate to > check it using pci host IDs. Right, it's just that "running on KVM" is too coarse grained, we just need a way to somehow distinguish between "known/good" and "unknown/buggy" configurations. -- Vitaly