linux-kernel - Re: [PATCH v3] xen/balloon: Mark unallocated host memory as UNUSABLE

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Message-ID: <14100e87-ba75-3ebd-e39d-f1df2b298c8c@suse.com>
Date:   Wed, 20 Dec 2017 18:33:17 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xen.org, linux-kernel@...r.kernel.org
Cc:     helgaas@...nel.org, christian.koenig@....com, JBeulich@...e.com
Subject: Re: [PATCH v3] xen/balloon: Mark unallocated host memory as UNUSABLE

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@...cle.com>

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


Juergen