From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacob Gorm Hansen Subject: Re: Question about hyper-threading of domains Date: Fri, 29 Apr 2005 13:10:36 -0700 Message-ID: <427294BC.6000402@diku.dk> References: <42728E37.2000502@diku.dk> <4ad99e05050429125764ad281b@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4ad99e05050429125764ad281b@mail.gmail.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Lars Roland Cc: xen-devel List-Id: xen-devel@lists.xenproject.org Lars Roland wrote: > Seans fair enough - Out of curiosity have you published these > measurements anywere ? No nothing yet, apart from the iperf numbers posted previously to this list. >>I previously stated that using small address spaces means giving up >>driver isolation, but I think that with the right use of segments that >>should not be necessary, so there is no trade-off with regards to isolation. > > > Could you explain a little further how excalty you plan to avoid this > - I have been digging into this myslef and It is not obvious to me how > this can be achived, I have not implemented this, and perhaps I am not understanding the x86 docs correctly, but it seems I can set up and expands-down segment to confine dom0 to its allowed range of addresses (0xf0000000 - 0xfc000000). If that does not work, I can move dom0 to the range 0x0 - 0x0c000000, and use the segment base to move it to 0xf0000000. The latter approach will require that I fix up copy_from_user and friends inside Xen to take this into account, but that seems doable. > Yes please - I have the time (and hardware) to check this. I will try to roll something up later today or tomorrow, before flying to Boston for NSDI. Jacob