Re: [Xen-devel] Any available page table entry bits in Xen??

To:	Xen-devel@xxxxxxxxxxxxxxxxxxx
Subject:	Re: [Xen-devel] Any available page table entry bits in Xen??
From:	"Mike Sun" <msun@xxxxxxxxxx>
Date:	Sat, 18 Oct 2008 22:14:25 -0400
Cc:
Delivery-date:	Sat, 18 Oct 2008 19:14:49 -0700
Dkim-signature:	v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:sender :to:subject:in-reply-to:mime-version:content-type :content-transfer-encoding:content-disposition:references :x-google-sender-auth; bh=Auaj19gPdvPoLxm1aU67hYmL401iMAFgJIJSIR8eDD4=; b=xcs9M85pSNVWN8yJui7vioyg+Kve+z8F9j1l6juSMpZORIBx/5VS/TmoKM7ejpxsH0 TbhHzDIT6Vv+eLwqchRGpyJBEjJdKCBl2AMY+qZmyuHMd94t8d4AJmGnAf4iToI8oItQ Yee1F2ori0viCJyXg1SY9Q2mH2NyxVNF7/mhU=
Domainkey-signature:	a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:sender:to:subject:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references:x-google-sender-auth; b=MKAOuyj1uwmXrknwGnjPJ1/5c+sziwdt3hMG+M/3ESgQWnE2W6jyNimM3QcqEbkwLN lYE9TZFOAJoYdB5XdEPU/IKywGDMNp+SOFA60Z8GmGu/6SLViSGUAaUEfusq7x2KyDb9 7BNLtsKxyXMdeGnnKCWH/NvkeSCevfYPmqoXg=
Envelope-to:	www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to:	<48FA1256.4070802@xxxxxxxxxx>
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>
References:	<48FA1256.4070802@xxxxxxxxxx>
Sender:	xen-devel-bounces@xxxxxxxxxxxxxxxxxxx

Hi Min,

> I'd like to know if there's any available bit in page table entries, on
> x86_32 (no pae),
> especially on L1 page table entry. It seems to me that all bits are used by
> Xen.

Could you clarify?  Are you referring to PTEs for para-virtualized
guests (without translation) or fully translated domains like HVM
guest with shadow paging?

I think for PV guests you're right, the PV guest OS cannot use of the
bits in the PTE.  Some of those bits are used by Xen (though somehow I
vaguely remember that though Xen reserves the use of those bits, they
may not actually be used).

For HVM guests, the guest PTEs will carry whatever the guest OS uses,
and in the shadow PTEs, I believe there are some bits not used by Xen
(not totally sure).

Mike

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

WARNING - OLD ARCHIVES

xen-devel

Re: [Xen-devel] Any available page table entry bits in Xen??