> -----Original Message----- > From: Alexander Graf [mailto:agraf@xxxxxxx] > Sent: Wednesday, February 03, 2010 6:14 PM > To: Liu Yu-B13201 > Cc: hollis@xxxxxxxxxxxxxx; kvm-ppc@xxxxxxxxxxxxxxx; > kvm@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 4/4] kvmppc/booke: exit_nr fixup for > guest debug single step > > Liu Yu-B13201 wrote: > > > > > > > >> -----Original Message----- > >> From: kvm-ppc-owner@xxxxxxxxxxxxxxx > >> [mailto:kvm-ppc-owner@xxxxxxxxxxxxxxx] On Behalf Of Alexander Graf > >> Sent: Wednesday, February 03, 2010 5:03 PM > >> To: Liu Yu-B13201 > >> Cc: hollis@xxxxxxxxxxxxxx; kvm-ppc@xxxxxxxxxxxxxxx; > >> kvm@xxxxxxxxxxxxxxx; Liu Yu-B13201 > >> Subject: Re: [PATCH 4/4] kvmppc/booke: exit_nr fixup for > >> guest debug single step > >> > >> > >> Am 03.02.2010 um 08:53 schrieb Liu Yu <yu.liu@xxxxxxxxxxxxx>: > >> > >> > >>> As BOOKE doesn't have hardware support for virtualization, > >>> hardware never know who's guest and host. > >>> > >>> When enable hardware single step in guest, > >>> we cannot disabled it at the point we switch back to host. > >>> > >> Why not? We directly arrive in our code. So we can just > >> disable it, no? > >> > >> Or does that break when you'd try to debug the guest > >> interrupt handlers? > >> > > > > That's the hardware limitition. > > Assume received itlb miss interrupt, but it doesn't clear > MSR_DE in MSR, > > so on the exit path single step still work and then debug > interrupt is > > triggled. > > > > MSRDE is set to 0 by critical class interrupts > unless Category E.ED is supported, by Debug > interrupts, and by Machine Check interrupts, > and is left unchanged by all other interrupts. > > Great. > > So when single stepping is enabled, you jump into the guest, > get an itlb > miss, get out, still have DE set, get in KVM's own DE handler and can > process things from there. > > Could you check if the debug instruction was on PR=0? If so, you can > just rfi and be good, right? > Hr? The moment we found this happen we've already saved the guest and loaded host on exit path Rfi will make exit path again which means save guest again. -- 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
