On 08/01/15 14:00, Jan Beulich wrote: >>>> On 08.01.15 at 14:25, <andrew.coop...@citrix.com> wrote: >> do_debug() is capable of correctly dealing with #DB exceptions in guest >> context, and indeed needs to be as the 'icebp' instruction skips the DPL >> check anyway. > I don't follow: ICEBP doesn't check DPL, right, but what does setting > DPL to 3 buy us? Other than for INTO and INT3, we don't want to > encourage use of INT $0x01 instructions, nor am I aware of anyone > commonly using them. Yet afaict only they would be affected by your > change. Actual #DB, just like any other hardware exceptions, don't > consider DPL just like ICEBP doesn't. > > Jan >
I noticed it as I was attempting to get my debugtraps test case working for PV guests, which does indeed use 'int $0x1'. But as you point out, it is only 'int $0x1' we would gain a fastpath for, which doesn't really make it worthwhile. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
