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From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Olaf Hering <olaf@aepfle.de>,
	boris.ostrovsky@oracle.com, david.vrabel@citrix.com
Cc: xen-devel@lists.xen.org
Subject: Re: identify a Xen PV domU to fix devmem_is_allowed
Date: Mon, 29 Feb 2016 10:10:00 -0500	[thread overview]
Message-ID: <20160229151000.GA17154@char.us.oracle.com> (raw)
In-Reply-To: <20160229102849.GA18202@aepfle.de>

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.

> 
> Would this change be the correct fix?

.. A fix for what issue?
> 
> +++ b/arch/x86/mm/init.c
> @@ -637,7 +637,7 @@ void __init init_mem_mapping(void)
>  int devmem_is_allowed(unsigned long pagenr)
>  {
>         if (pagenr < 256)
> -               return 1;
> +               return !xen_pv_domain();
>         if (iomem_is_exclusive(pagenr << PAGE_SHIFT))
>                 return 0;
>         if (!page_is_ram(pagenr))
> 
> Olaf
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel

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  reply	other threads:[~2016-02-29 15:10 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 [this message]
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
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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