From: Keir Fraser <keir@xen.org>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
Ian Campbell <Ian.Campbell@eu.citrix.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Jeremy Fitzhardinge <jeremy@goop.org>,
"hpa@zytor.com" <hpa@zytor.com>,
Jan Beulich <JBeulich@novell.com>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
Konrad Rzeszutek Wilk <konrad@kernel.org>
Subject: Re: [PATCH 6/8] xen/debug: WARN_ON when 1-1 but no _PAGE_IOMAP flag set.
Date: Thu, 06 Jan 2011 22:17:06 +0000 [thread overview]
Message-ID: <C94BEFE2.11452%keir@xen.org> (raw)
In-Reply-To: <20110106215952.GB18722@dumpdata.com>
On 06/01/2011 21:59, "Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com> 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
next prev parent reply other threads:[~2011-01-06 22:17 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-30 19:48 [PATCH RFC v2] Consider E820 non-RAM and E820 gaps as 1-1 mappings Konrad Rzeszutek Wilk
2010-12-30 19:48 ` [PATCH 1/8] xen: Mark all initial reserved pages for the balloon as INVALID_P2M_ENTRY Konrad Rzeszutek Wilk
2011-01-04 16:34 ` Ian Campbell
2011-01-04 16:45 ` Konrad Rzeszutek Wilk
2010-12-30 19:48 ` [PATCH 2/8] xen/mmu: Add the notion of identity (1-1) mapping Konrad Rzeszutek Wilk
2011-01-04 16:53 ` Ian Campbell
2011-01-04 16:59 ` Ian Campbell
2011-01-04 17:20 ` [Xen-devel] " Ian Campbell
2011-01-04 19:24 ` Konrad Rzeszutek Wilk
2011-01-05 14:03 ` Ian Campbell
2010-12-30 19:48 ` [PATCH 3/8] xen/setup: Set identity mapping for non-RAM E820 and E820 gaps Konrad Rzeszutek Wilk
2011-01-04 17:18 ` Ian Campbell
2011-01-04 18:38 ` Konrad Rzeszutek Wilk
2011-01-04 19:27 ` Ian Campbell
2011-01-04 21:28 ` Konrad Rzeszutek Wilk
2010-12-30 19:48 ` [PATCH 4/8] xen/mmu: Warn against races Konrad Rzeszutek Wilk
2010-12-30 19:48 ` [PATCH 5/8] xen/debug: Print out all pages in the P2M Konrad Rzeszutek Wilk
2010-12-30 19:48 ` [PATCH 6/8] xen/debug: WARN_ON when 1-1 but no _PAGE_IOMAP flag set Konrad Rzeszutek Wilk
2011-01-04 17:24 ` Ian Campbell
2011-01-04 18:46 ` Konrad Rzeszutek Wilk
2011-01-04 19:20 ` Ian Campbell
2011-01-06 19:50 ` Stefano Stabellini
2011-01-06 20:17 ` Keir Fraser
2011-01-06 21:59 ` Konrad Rzeszutek Wilk
2011-01-06 22:17 ` Keir Fraser [this message]
2010-12-30 19:48 ` [PATCH 7/8] xen/mmu: Introduce IDENTITY_FRAME_BIT Konrad Rzeszutek Wilk
2011-01-04 16:26 ` Ian Campbell
2011-01-04 16:45 ` Konrad Rzeszutek Wilk
2010-12-30 19:48 ` [PATCH 8/8] xen/mmu: Set _PAGE_IOMAP if PFN is in identity P2M Konrad Rzeszutek Wilk
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