From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=162.221.156.55; helo=smtp03.citrix.com; envelope-from=prvs=9742ee4c2=anthony.perard@citrix.com; receiver=edk2-devel@lists.01.org Received: from SMTP03.CITRIX.COM (smtp03.citrix.com [162.221.156.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 022E8211DB422 for ; Tue, 19 Mar 2019 07:04:55 -0700 (PDT) X-IronPort-AV: E=Sophos;i="5.58,498,1544486400"; d="scan'208";a="81001537" Date: Tue, 19 Mar 2019 14:03:19 +0000 From: Anthony PERARD To: Igor Druzhinin CC: , , , , , Message-ID: <20190319140319.GJ11621@perard.uk.xensource.com> References: <1551876056-28223-1-git-send-email-igor.druzhinin@citrix.com> <1551876056-28223-2-git-send-email-igor.druzhinin@citrix.com> <20190314174121.GB11621@perard.uk.xensource.com> <096a1987-a898-9896-8ffd-9fc8512e25f6@citrix.com> MIME-Version: 1.0 In-Reply-To: <096a1987-a898-9896-8ffd-9fc8512e25f6@citrix.com> User-Agent: Mutt/1.11.3 (2019-02-01) Subject: Re: [PATCH RESEND 1/3] OvmfPkg/XenSupport: remove usage of prefetchable PCI host bridge aperture X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 19 Mar 2019 14:04:57 -0000 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline On Thu, Mar 14, 2019 at 07:45:56PM +0000, Igor Druzhinin wrote: > On 14/03/2019 17:41, Anthony PERARD wrote: > > Hi, > > > > On Wed, Mar 06, 2019 at 12:40:54PM +0000, Igor Druzhinin wrote: > >> This aperture doesn't exist in OVMF and trying to use it causes > > > > I'm trying to understand what you mean by writing "doesn't exist in > > OVMF". Are prefetchable BAR not handled by ScanForRootBridges() ? > > Or is it the emulation of the config space that isn't correct? > > Maybe QEMU should lies about a BAR been prefetchable? > > The problem here is: hvmloader places BARs initially disregarding > prefetchable bit in an arbitrary order because essentially there is only > 1 aperture for the host bridge in emulated system under Xen (and KVM as > well). In PcatPciRootBridgeParseBars() we construct apertures for high > level OVMF code by reading the BAR placement information after > hvmloader. It often appears that there are prefetchable and > non-prefetchable BARs coexist with each other and make prefetchable and > non-prefetchable apertures overlap. This eventually triggers an > assertion in high level OVMF code because that shouldn't happen. Thanks for the explanation. Could you add it to the patch description? > OVMF for KVM is not using prefetchable BAR at all - see > PciHostBridgeGetRootBridges() in which it passes mNonExistAperture dummy > object to high level code. I think it's wrong to construct a > prefetchable aperture for Xen and this code should be removed as it's > done for QEMU-KVM. Do you think this patch needs to do that? It would be nice to remove the code that isn't useful so feel free to do it and/or keep the current patch with the description updated. Thanks, -- Anthony PERARD