On Sun, 20 Dec 2020 11:13:57 +0100 David Hildenbrand <david@xxxxxxxxxx> wrote: > On 18.12.20 15:18, Claudio Imbrenda wrote: > > Correctly handle the MVPG instruction when issued by a VSIE guest. > > > > I remember that MVPG SIE documentation was completely crazy and full > of corner cases. :) you remember correctly > Looking at arch/s390/kvm/intercept.c:handle_mvpg_pei(), I can spot > that > > 1. "This interception can only happen for guests with DAT disabled > ..." 2. KVM does not make use of any mvpg state inside the SCB. > > Can this be observed with Linux guests? a Linux guest will typically not run with DAT disabled > Can I get some information on what information is stored at [0xc0, > 0xd) inside the SCB? I assume it's: > > 0xc0: guest physical address of source PTE > 0xc8: guest physical address of target PTE yes (plus 3 flags in the lower bits of each) > > Also, which conditions have to be met such that we get a > ICPT_PARTEXEC: > > a) State of guest DAT (I assume off?) > b) State of PTEs: What happens if there is no PTE (I assume we need > two PTEs, otherwise no such intercept)? I assume we get an intercept > if one of both PTEs is not present or the destination PTE is > protected. Correct? we get the intercept if the guest has DAT off, and at least one of the host PTEs is invalid (and I think if the destination is valid but protected) > So, when we (g1) get an intercept for g3, can we be sure 0xc0 and 0xc8 > in the scb are both valid g1 addresses pointing at our PTE, and what > do we know about these PTEs (one not present or destination > protected)? we only know that at least one of the following holds true: * source invalid * destination invalid * destination protected there is a bit that tells us if the destination was protected (bit 62), but that does not exclude an invalid source > [...] > > /* > > * Run the vsie on a shadow scb and a shadow gmap, without any > > further > > * sanity checks, handling SIE faults. > > @@ -1063,6 +1132,10 @@ static int do_vsie_run(struct kvm_vcpu > > *vcpu, struct vsie_page *vsie_page) if ((scb_s->ipa & 0xf000) != > > 0xf000) scb_s->ipa += 0x1000; > > break; > > + case ICPT_PARTEXEC: > > + if (scb_s->ipa == 0xb254) > > Old code hat "/* MVPG only */" - why is this condition now necessary? old code was wrong ;) > > + rc = vsie_handle_mvpg(vcpu, vsie_page); > > + break; > > } > > return rc; > > } > > > >
