Subject: Re: [PATCH v3] xen/balloon: Mark unallocated host memory as UNUSABLE
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>, xen-devel@lists.xen.org,
        linux-kernel@vger.kernel.org
Cc: helgaas@kernel.org, christian.koenig@amd.com, JBeulich@suse.com
References: <1513778746-6155-1-git-send-email-boris.ostrovsky@oracle.com>
From: Juergen Gross <jgross@suse.com>
Message-ID: <14100e87-ba75-3ebd-e39d-f1df2b298c8c@suse.com>
Date: Wed, 20 Dec 2017 18:33:17 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.5.0
MIME-Version: 1.0
In-Reply-To: <1513778746-6155-1-git-send-email-boris.ostrovsky@oracle.com>
Content-Type: text/plain; charset=utf-8
Content-Language: de-DE
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 765
Lines: 20

On 20/12/17 15:05, Boris Ostrovsky wrote:
> Commit f5775e0b6116 ("x86/xen: discard RAM regions above the maximum
> reservation") left host memory not assigned to dom0 as available for
> memory hotplug.
> 
> Unfortunately this also meant that those regions could be used by
> others. Specifically, commit fa564ad96366 ("x86/PCI: Enable a 64bit BAR
> on AMD Family 15h (Models 00-1f, 30-3f, 60-7f)") may try to map those
> addresses as MMIO.
> 
> To prevent this mark unallocated host memory as E820_TYPE_UNUSABLE (thus
> effectively reverting f5775e0b6116) and keep track of that region as
> a hostmem resource that can be used for the hotplug.
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen