[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] Grant tables from dom0 userspace?

  • To: "King, Steven R" <steven.r.king@xxxxxxxxx>
  • From: "Andrew Warfield" <andrew.warfield@xxxxxxxxxxxx>
  • Date: Thu, 9 Mar 2006 10:59:28 -0800
  • Cc: "Cihula, Joseph" <joseph.cihula@xxxxxxxxx>, Jacob Gorm Hansen <jacobg@xxxxxxx>, xen-devel Devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Thu, 09 Mar 2006 19:00:17 +0000
  • Domainkey-signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=jIDzDIf9LpqJ7JlWxfASBHjGkiZbIyS2Wo1fvO1TkO3uThnzwitGiD2m49SbFgkJsrHtebxto2LDS9YHwr8Xyyv96VJrYSGt0zqFshywSE/Gx74Ctha8U9khd7M6VfgWlVjPfHfuTbSYeHPFflnhc0RPNRLEuanh2pqOLQ5XI00=
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

Hi Steven,

> I've hacked around many of
> the problems, such as implicit unmapping of grant references, but others
> remain.  Some of the issues have no resolution in the grant table
> architecture.

   It would be quite useful to know what specific problems you have
encountered in this effort as insight for future versions of the code.
 The main problem that I have encountered in user-level foreign page
mappings is (as discussed previously) that Linux is a bit hasty in
blowing away user virtual memory areas, and doesn't provide a good
mechanism to safely unmap the pages.  The kernel has all the
information it needs to do the right thing though, and I think this
should be reasonably fixed in the future -- i don't see a compelling
reason for Xen to do extra book-keeping to cover for something that
the OS could just as easily do.  Especially for something like
cross-VM mappings, which don't exist in the non-virtualized system. 
Are there implicit unmapping problems that you thing would remain
unsolved if, for instance, there was a vm area destructor early enough
to allow the OS to properly unmap active grants?

   When you say, "others remain," can you provide a little more detail?


Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.