Re: Question about hyper-threading of domains

[Jacob Gorm Hansen <jacobg@diku.dk>]

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