Rusty Russell wrote: > On Tue, 2007-07-10 at 10:19 +0300, Avi Kivity wrote: > >> Rusty Russell wrote: >> >>> Exactly, if we have two at the same time, they need to know about each >>> other. Providing infrastructure which lets them avoid thinking about it >>> is the wrong direction. >>> >>> >> With a kvm-specific hook, they can't stop on each other (there can only >> be one). >> With a list, they don't stomp on each other. >> With a struct preempt_ops but no list, as you propose, they can and will >> stomp on each other. >> > > I'm not talking about the actual overwriting of someone else's hook. > I'm talking about semantic conflicts involving the actual CPU state. > > If I'm lazily restoring some CPU state because I know I don't use it, > and you're lazily restoring some CPU state because you don't use it, we > need to make sure that state doesn't intersect: ie. we need to be aware > of each other. Only providing a single hook per task forces the second > user to think about it (maybe that lazy state saving needs to be > extracted into common code). >
Well, if there's another user of VT instructions, then we certainly need to have something central to coordinate it. No API can prevent this, at some point we'll forced to use common sense. >> I guess I can put it in arch specific code, but that means both i386 and >> x86_64. >> >> Once we have another user we can try to generalize it. >> > > The problem is that the arch hooks are in the wrong place: > > Yes. >>> Which brings us to the question: why do you want interrupts enabled? >>> >> The sched in hook (vcpu_load) sometimes needs to issue an IPI in order >> to flush the VT registers from another cpu into memory. >> > > OK, I'll have to go away and read the code for this. > > BTW, I have no problem with #ifdef KVM-style code in arch-specifics. > It's kernel/sched.c which is jarring... > We don't want you jarred, do we? I'll prepare a non-kvm-specific patch for review later on. But I can't bring myself to do a single generic hook (it's impossible to use correctly); it will be an hlist-based thing. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
