From: Jan Beulich <jbeulich@suse.com>
To: Julien Grall <julien.grall@arm.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
George Dunlap <George.Dunlap@eu.citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Ian Jackson <ian.jackson@eu.citrix.com>,
Jeff Kubascik <jeff.kubascik@dornerworks.com>,
Tim Deegan <tim@xen.org>,
Stewart.Hildebrand@dornerworks.com,
xen-devel@lists.xenproject.org, Jarvis.Roach@dornerworks.com
Subject: Re: [Xen-devel] [PATCH] xen/page_alloc: Keep away MFN 0 from the buddy allocator
Date: Fri, 9 Aug 2019 15:38:56 +0200 [thread overview]
Message-ID: <e9d6353c-fd4d-116e-2531-7db46abf2b23@suse.com> (raw)
In-Reply-To: <20190809121440.5668-1-julien.grall@arm.com>
On 09.08.2019 14:14, Julien Grall wrote:
> Combining of buddies happens only such that the resulting larger buddy
> is still order-aligned. To cross a zone boundary while merging, the
> implication is that both the buddy [0, 2^n-1] and the buddy
> [2^n, 2^(n+1)] are free.
[2^n, 2^(n+1)-1]
You may want to add that merging across zone boundaries is what we
need to prevent.
> Ideally we want to fix the allocator, but for now we can just prevent
> adding the MFN 0 in the allocator.
>
> On x86, the MFN 0 is already kept away from the buddy allocator. So the
> bug can only happen on Arm platform where the first memory bank is
> starting at 0.
>
> As this is a specific to the allocator, the MFN 0 is removed in the common code
> to cater all the architectures (current and future).
>
> Reported-by: Jeff Kubascik <jeff.kubascik@dornerworks.com>
> Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
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next prev parent reply other threads:[~2019-08-09 13:39 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-09 12:14 [Xen-devel] [PATCH] xen/page_alloc: Keep away MFN 0 from the buddy allocator Julien Grall
2019-08-09 13:38 ` Jan Beulich [this message]
2019-08-09 18:15 ` Stewart Hildebrand
2019-08-09 18:23 ` Stefano Stabellini
2019-08-09 18:34 ` Stewart Hildebrand
2019-08-09 18:35 ` Julien Grall
2019-08-12 6:16 ` Jan Beulich
2019-08-12 6:01 ` Jan Beulich
2019-08-09 17:55 ` Stefano Stabellini
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