Re: [PATCH v19 059/130] KVM: x86/tdp_mmu: Don't zap private pages for unsupported cases

Edgecombe, Rick P
2024-03-25T23:21:21Z

On Mon, 2024-03-25 at 16:10 -0700, Isaku Yamahata wrote:
> > > My understanding is that Sean prefers to exit to userspace when KVM can't handle something,
> > > versus
> > > making up behavior that keeps known guests alive. So I would think we should change this patch
> > > to
> > > only be about not using the zapping roots optimization. Then a separate patch should exit to
> > > userspace on attempt to use MTRRs. And we ignore the APIC one.
> > >
> > > This is trying to guess what maintainers would want here. I'm less sure what Paolo prefers.
> >
> > When we hit KVM_MSR_FILTER, the current implementation ignores it and makes it
> > error to guest.  Surely we should make it KVM_EXIT_X86_{RDMSR, WRMSR}, instead.
> > It's aligns with the existing implementation(default VM and SW-protected) and
> > more flexible.
>
> Something like this for "112/130 KVM: TDX: Handle TDX PV rdmsr/wrmsr hypercall"
> Compile only tested at this point.

Seems reasonable to me. Does QEMU configure a special set of MSRs to filter for TDX currently?