From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <JBeulich@suse.com>
Subject: Re: [PATCH v4] hw/passthrough: Prevent QEMU from
 mapping PCI option ROM at address 0
Date: Mon, 12 May 2014 16:52:47 +0100
Message-ID: <53710A6F02000078000118D0@mail.emea.novell.com>
References: <1399909019-5812-1-git-send-email-malcolm.crossley@citrix.com>
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To: Malcolm Crossley <malcolm.crossley@citrix.com>
Cc: Ian.Jackson@citrix.com, Paul.Durrant@citrix.com, Ian.Campbell@citrix.com, xen-devel@lists.xen.org
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>>> On 12.05.14 at 17:36, <malcolm.crossley@citrix.com> wrote:
> The PCI option ROM BAR uses the LSB to indicate if the BAR is enabled.
> The AMD graphics driver sets the address bit's of the BAR to 0 but leaves 
> the
> LSB set to 1. Whilst this is not good practice, QEMU should be ignoring the
> non address parts of the BAR.

All you say above only warrants the PCI defined bits to be masked
off, ...

> This patch adds masking of the bits 0-11 (4k page) parts of the BAR
> before comparing the address to 0.

... i.e. 0-10 (2k).

Jan