Hi Marc,
On Thu, Oct 24, 2024 at 10:39:45AM +0100, Marc Zyngier wrote:
> Hi Mostafa,
>
> On Wed, 23 Oct 2024 18:12:43 +0100,
> Mostafa Saleh <smostafa@xxxxxxxxxx> wrote:
> >
> > Commit 5053c3f0519c ("KVM: arm64: Use hVHE in pKVM by default on CPUs with
> > VHE support") modified the behaviour of "kvm-arm.mode=protected" without
> > the updating the kernel parameters doc.
> >
> > Update it to match the current implementation.
> >
> > Cc: Will Deacon <will@xxxxxxxxxx>
> > Cc: Marc Zyngier <maz@xxxxxxxxxx>
> >
> > Signed-off-by: Mostafa Saleh <smostafa@xxxxxxxxxx>
> > ---
> > Documentation/admin-guide/kernel-parameters.txt | 6 +++++-
> > 1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index bb48ae24ae69..59a0dd7e2de6 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -2723,8 +2723,12 @@
> > nvhe: Standard nVHE-based mode, without support for
> > protected guests.
> >
> > - protected: nVHE-based mode with support for guests whose
> > + protected: hVHE-based mode with support for guests whose
> > state is kept private from the host.
> > + In case hVHE is not supported in hardware, it will
>
> nit: it is VHE that is supported or not, hVHE is only a SW concept.
>
> > + boot with protected nVHE.
> > + nVHE protected mode can still be forced on VHE systems
> > + using "kvm_arm.mode=protected arm64_sw.hvhe=0 id_aa64mmfr1.vh=0"
>
> This opens another question: none of the arm_sw.*, nor any of the
> id_aa64* parameters are described (basically, anything that's in
> arch/arm64/kernel/pi/id_override.c). What should we do about these?
Yes, I mainly added this, to make it easier if someone wants to boot to
protected nVHE so they don't have to go through the code, but I can
remove it if it's confusing.
>
>
>
> >
> > nested: VHE-based mode with support for nested
> > virtualization. Requires at least ARMv8.3
>
> Huh, another nit to fix. We only support nested with ARMv8.4 (with
> FEAT_NV2), as the ARMv8.3 version (the original FEAT_NV) is too ugly
> for words.
>
> Mind addressing this?
Sure, I will update it in v2.
Thanks,
Mostafa
>
> Thanks!
>
> M.
>
> --
> Without deviation from the norm, progress is not possible.
