Re: [PATCH v3 59/75] x86/sev-es: Handle MONITOR/MONITORX Events

Joerg Roedel
2020-06-11T13:10:45Z

On Tue, May 19, 2020 at 11:38:45PM -0700, Sean Christopherson wrote:
> On Tue, Apr 28, 2020 at 05:17:09PM +0200, Joerg Roedel wrote:
> > +static enum es_result vc_handle_monitor(struct ghcb *ghcb,
> > + struct es_em_ctxt *ctxt)
> > +{
> > + phys_addr_t monitor_pa;
> > + pgd_t *pgd;
> > +
> > + pgd = __va(read_cr3_pa());
> > + monitor_pa = vc_slow_virt_to_phys(ghcb, ctxt->regs->ax);
> > +
> > + ghcb_set_rax(ghcb, monitor_pa);
> > + ghcb_set_rcx(ghcb, ctxt->regs->cx);
> > + ghcb_set_rdx(ghcb, ctxt->regs->dx);
> > +
> > + return sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_MONITOR, 0, 0);
>
> Why? If SVM has the same behavior as VMX, the MONITOR will be disarmed on
> VM-Enter, i.e. the VMM can't do anything useful for MONITOR/MWAIT. I
> assume that's the case given that KVM emulates MONITOR/MWAIT as NOPs on
> SVM.

Not sure if it is disarmed on VMRUN, but the MONITOR/MWAIT instructions
are part of the GHCB spec, so they are implemented here.

Joerg