From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: boris.ostrovsky@oracle.com, Olaf Hering <olaf@aepfle.de>,
david.vrabel@citrix.com, xen-devel@lists.xen.org
Subject: Re: identify a Xen PV domU to fix devmem_is_allowed
Date: Tue, 1 Mar 2016 09:34:05 -0500 [thread overview]
Message-ID: <20160301143405.GD21829@char.us.oracle.com> (raw)
In-Reply-To: <56D57F4F02000078000D7BD4@prv-mh.provo.novell.com>
On Tue, Mar 01, 2016 at 03:38:55AM -0700, Jan Beulich wrote:
> >>> On 29.02.16 at 16:10, <konrad.wilk@oracle.com> wrote:
> > On Mon, Feb 29, 2016 at 11:28:49AM +0100, Olaf Hering wrote:
> >> What is the correct way to identify a Xen PV domU in the kenrel?
> >> devmem_is_allowed() used to disable access to pages < 256 in domU.
> >> With pvops this check was removed, or never ported forward.
> >
> > CC-ing Boris and Daniel.
> >
> > Why is this needed? The first 640KB of memory in a guest are
> > RAM pages with no BIOS data in it.
>
> Exactly: devmem_is_allowed() is specifically meant to return true
> if and only if the page is not RAM or otherwise special. The
> question just is whether what Olaf suggested is also correct for
> Dom0 - I don't recall whether the low 1Mb gets 1:1 mapped in
> that case.
Would it be just better to change that code to scan the E820 instead
of using hard-coded values?
>
> Jan
>
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next prev parent reply other threads:[~2016-03-01 14:34 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-29 10:28 identify a Xen PV domU to fix devmem_is_allowed Olaf Hering
2016-02-29 15:10 ` Konrad Rzeszutek Wilk
2016-02-29 15:29 ` Olaf Hering
2016-02-29 18:32 ` Boris Ostrovsky
2016-03-01 15:14 ` Olaf Hering
2016-03-01 10:38 ` Jan Beulich
2016-03-01 14:34 ` Konrad Rzeszutek Wilk [this message]
2016-03-01 14:45 ` Boris Ostrovsky
2016-03-15 16:57 ` Olaf Hering
2016-03-15 18:56 ` Boris Ostrovsky
2016-03-21 21:29 ` Boris Ostrovsky
2016-03-22 18:37 ` Boris Ostrovsky
2016-03-23 8:28 ` Olaf Hering
2016-06-06 21:17 ` Olaf Hering
2016-03-01 16:23 ` Olaf Hering
2016-03-01 15:29 ` David Vrabel
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