This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


[Xen-devel] Re: [PATCH 6/8] xen/debug: WARN_ON when 1-1 but no _PAGE_IOM

To: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH 6/8] xen/debug: WARN_ON when 1-1 but no _PAGE_IOMAP flag set.
From: Keir Fraser <keir@xxxxxxx>
Date: Thu, 06 Jan 2011 22:17:06 +0000
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx>, "hpa@xxxxxxxxx" <hpa@xxxxxxxxx>
Delivery-date: Thu, 06 Jan 2011 14:18:47 -0800
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:sender:user-agent:date :subject:from:to:cc:message-id:thread-topic:thread-index:in-reply-to :mime-version:content-type:content-transfer-encoding; bh=NYtg83gaiMl4JAIEkHnBfm6+u1g1sNUaNgCw+o5rXvE=; b=Hu40M0nXx7jFN5ngiruee+5KjR2kh1bhXB72LLqY15Dbayvea75vxZIo22tNzoiQXG RF0nqtPKOexek+nU2rLJq3TDYF3ZWmLZWNYpFtqVbPBybPEQtbj/fhGesM4dGjB9WRgu Wxbzq4wd/ltKnCkb4hEZtAuMUgnQ7ek8FChNg=
Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:user-agent:date:subject:from:to:cc:message-id:thread-topic :thread-index:in-reply-to:mime-version:content-type :content-transfer-encoding; b=QUPcZkXVIvYekx8FIJF80EE6lbzBEtxwu5E9cuqfZ58aYTt50gcA0FiOzsiSRiCfPR Cn4cou4cz9F6ke9tJtAeMbVxxRe0p8K0Xu7t3g9xuT7l8vGAzU8k2ZKw83bfFrDNebq9 0RIz9WaBteUimf37tgo/cIGlFtm+5B5jTfbQs=
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <20110106215952.GB18722@xxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: Acut73OxLKwQLQHZRk6BbPSlgUOCiw==
Thread-topic: [PATCH 6/8] xen/debug: WARN_ON when 1-1 but no _PAGE_IOMAP flag set.
User-agent: Microsoft-Entourage/
On 06/01/2011 21:59, "Konrad Rzeszutek Wilk" <konrad.wilk@xxxxxxxxxx> wrote:

>> Always 0x55...55 (for m2p entries that exist), else page fault on access to
>> the non-existent m2p entry (m2p entries only guaranteed to exist for ram).
>> Perhaps the 0xff...ff values come from Linux's own fixup code handling a
>> faulting read access of the m2p array? If so you could return 0x55...55
>> instead and avoid checking for 0xff...ff. I really don't know how you could
>> get 0xff...ff for non-RAM pages from Xen itself.
> The non-RAM pages are assinged to a DOMID_IO (arch_init_memory), for example:
>  298     /* First 1MB of RAM is historically marked as I/O. */
>  299     for ( i = 0; i < 0x100; i++ )
>  300         share_xen_page_with_guest(mfn_to_page(i), dom_io,
> XENSHARE_writable);
> and share_xen_page.. sets that page to INVALID_M2P_ENTRY.
> But I could also be reading the code wrongly?

You're right, I missed that.

 -- Keir

Xen-devel mailing list