Re: [PATCH v3 3/3] arm64/kvm: Fine grain _EL2 system registers list that affect nested virtualization

[Marc Zyngier]

On 2023-10-12 16:22, Eric Auger wrote:
> Hi Miguel,
>
> On 10/11/23 20:01, Miguel Luis wrote:
> > Implement a fine grained approach in the _EL2 sysreg ranges.
> >
> > Fixes: d0fc0a2519a6 ("KVM: arm64: nv: Add trap forwarding for 
> > HCR_EL2")
> > Signed-off-by: Miguel Luis <miguel.luis@xxxxxxxxxx>
> > ---
> >  arch/arm64/kvm/emulate-nested.c | 88 
> > ++++++++++++++++++++++++++++++---
> >  1 file changed, 82 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/emulate-nested.c 
> > b/arch/arm64/kvm/emulate-nested.c
> > index 9ced1bf0c2b7..3af49e130ee6 100644
> > --- a/arch/arm64/kvm/emulate-nested.c
> > +++ b/arch/arm64/kvm/emulate-nested.c
> > @@ -648,15 +648,91 @@ static const struct encoding_to_trap_config 
> > encoding_to_cgt[] __initconst = {
> >  	SR_TRAP(SYS_APGAKEYLO_EL1,	CGT_HCR_APK),
> >  	SR_TRAP(SYS_APGAKEYHI_EL1,	CGT_HCR_APK),
> >  	/* All _EL2 registers */
> > -	SR_RANGE_TRAP(sys_reg(3, 4, 0, 0, 0),
> > -		      sys_reg(3, 4, 3, 15, 7), CGT_HCR_NV),
> > +	SR_TRAP(SYS_VPIDR_EL2,		CGT_HCR_NV),
> I think you miss DBGVCR32_EL2

I don't think this register should be part of this list. We don't
support AArch32 with NV, and the spec says that DBGVCR32_EL2 UNDEFs
when EL1 doesn't support AArch32.

So the change that needs to happen is to inject an UNDEF when trapping
a DBGVCR32_EL2and not forward the trap to the guest.

Thanks,

        M.
--
Jazz is not dead. It just smells funny...