Re: [PATCH] KVM: arm64: Use different pointer authentication keys for pKVM

[Mostafa Saleh]

On Tue, Jun 13, 2023 at 5:27 PM Mostafa Saleh <smostafa@xxxxxxxxxx> wrote:
>
> Hi Oliver,
>
> On Tue, Jun 13, 2023 at 12:16:02PM +0000, Oliver Upton wrote:
> > On Tue, 16 May 2023 14:15:31 +0000, Mostafa Saleh wrote:
> > > When the kernel is compiled with CONFIG_ARM64_PTR_AUTH_KERNEL, it
> > > uses Armv8.3-Pauth for return address protection for the kernel code
> > > including nvhe code in EL2.
> > >
> > > Same keys are used in both kernel(EL1) and nvhe code(EL2), this is
> > > fine for nvhe but not when running in protected mode(pKVM) as the host
> > > can't be trusted.
> > >
> > > [...]
> >
> > Applied to kvmarm/next, thanks!
> >
> > [1/1] KVM: arm64: Use different pointer authentication keys for pKVM
> >       https://git.kernel.org/kvmarm/kvmarm/c/fb737685beee
> >
> > --
>
> Thanks! I did more testing and I found a bug in this patch.
>
> It seems there is another entry point for the kenrel where pauth was
> not handled properly "kvm_host_psci_cpu_entry", I will investigate this
> further and send V2.
>
> Sorry for the inconvenience!
>
> Thanks,
> Mostafa

I investigated the problem further and actually the bug is missing
isb() after updating
Pauth system registers at EL2, I sent a v2 with this fix.

Although when entering from kvm_host_psci_cpu_entry, the hyp keys are not used,
but this call directly exists to the host, so I believe this should be fine.