On Wed, Aug 19, 2020 at 8:26 AM Alexander Graf <graf@xxxxxxxxxx> wrote: > > > > On 18.08.20 23:15, Aaron Lewis wrote: > > > > SDM volume 3: 24.6.9 "MSR-Bitmap Address" and APM volume 2: 15.11 "MS > > intercepts" describe MSR permission bitmaps. Permission bitmaps are > > used to control whether an execution of rdmsr or wrmsr will cause a > > vm exit. For userspace tracked MSRs it is required they cause a vm > > exit, so the host is able to forward the MSR to userspace. This change > > adds vmx/svm support to ensure the permission bitmap is properly set to > > cause a vm_exit to the host when rdmsr or wrmsr is used by one of the > > userspace tracked MSRs. Also, to avoid repeatedly setting them, > > kvm_make_request() is used to coalesce these into a single call. > > > > Signed-off-by: Aaron Lewis <aaronlewis@xxxxxxxxxx> > > Reviewed-by: Oliver Upton <oupton@xxxxxxxxxx> > > This is incomplete, as it doesn't cover all of the x2apic registers. > There are also a few MSRs that IIRC are handled differently from this > logic, such as EFER. > > I'm really curious if this is worth the effort? I would be inclined to > say that MSRs that KVM has direct access for need special handling one > way or another. > Can you please elaborate on this? It was my understanding that the permission bitmap covers the x2apic registers. Also, I’m not sure how EFER is handled differently, but I see there is a separate conversation on that. This effort does seem worthwhile as it ensures userspace is able to manage the MSRs it is requesting, and will remain that way in the future. > > Alex > > > > Amazon Development Center Germany GmbH > Krausenstr. 38 > 10117 Berlin > Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss > Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B > Sitz: Berlin > Ust-ID: DE 289 237 879 > >
