On Mon, Jan 30, 2012 at 12:45:15PM +0200, Avi Kivity wrote: > On 01/30/2012 12:35 PM, Kevin Wolf wrote: > > Am 30.01.2012 09:55, schrieb Gleb Natapov: > > > On Mon, Jan 30, 2012 at 09:48:33AM +0100, Kevin Wolf wrote: > > >> Am 27.01.2012 20:52, schrieb Gleb Natapov: > > >>> On Fri, Jan 27, 2012 at 08:23:33PM +0100, Kevin Wolf wrote: > > >>>> I believe this should work with both VMX and SVM now. Gleb, Jörg, can one of > > >>>> you test this with SVM? I did some testing on my buggy processor and it looks > > >>>> as good as it gets, but it would be better if you could confirm. > > >>>> > > >>> You forgot to set cpl to 3 in vmcb in svm_set_rflags() when vm86 is enabled, no? > > >> > > >> SVM updates the CPL when the segment selector for CS is loaded. From a > > >> svm.c POV, segment selectors are updated immediately after set_rflags, > > >> so it wouldn't really make a difference to do it twice. > > >> > > > It is too subtle to rely on that. The fact is that checking cpl after > > > set_rflags provides incorrect value. This better be fixed. > > > > Depends on what value you consider to be correct between reloading > > eflags and reloading cs. I think it's logical and more consistent to say > > that CPL only changes when cs is reloaded, but you could argue that it's > > effective with the reload of rflags. It doesn't make a difference to > > guests, so we can decide to choose whatever we like. > > It's best to make it independent (like svm, and force vmx to emulate > this behaviour). Real mode forces cpl to 0, vm86 forces cpl to 3, > protected mode (and I think long mode) uses cs.rpl. This is what vmx does, not svm. svm checks vmcb->cpl that can be outdated during emulation. > Making it depend on > the mode causes subtle issues during the mode switch - if you switch > from real mode to protected mode while cs & 3 != 0 you end up with the > wrong cpl until the jmp instruction is executed. > > > > > Depending on what we decide on (Gleb and I disagree on this, so more > > input would be helpful), either VMX or SVM need a cleanup. I think it > > can be done independent from and on top of this fix. > > Right. IMO we should follow svm and make vmx be more flexible. > > One way to do it is to have a new variable for vmx cpl, and reconcile > all the places where cpl is stored (cs.rpl, ss.rpl, cr0.pe, rflags.vm) > just before entry. If we can't reconcile it, we have to emulate. > > > > -- > error compiling committee.c: too many arguments to function -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
