Re: [edk2-devel] [PATCH 2/3] ArmVirtPkg/ArmVirtQemu: Expose TRNG hypercall via RngDxe if implemented

["Ard Biesheuvel" <ardb@kernel.org>]

On Fri, 18 Nov 2022 at 17:48, PierreGondois <pierre.gondois@arm.com> wrote:
>
> Hello Ard,
>
> On 11/10/22 14:47, Ard Biesheuvel wrote:
> > Currently, we only expose the EFI_RNG_PROTOCOL in ArmVirtQemu if QEMU
> > provides a virtio-rng device, and it doesn't do so by default.
> >
> > Given that KVM exposes the ARM architected TRNG service (and has done so
> > for a while now), let's incorporate the RngDxe driver which has recently
> > grown support for the ARM firmware/hypervisor service.
> >
> > If both the service and the virtio device are available, two
> > implementations of the RNG protocol will be exposed, but this is fine:
> > callers that don't care about the distinction will grab the first one
> > available.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> >   ArmVirtPkg/ArmVirtQemu.dsc           | 11 +++++++++++
> >   ArmVirtPkg/ArmVirtQemuFvMain.fdf.inc |  5 +++++
> >   ArmVirtPkg/ArmVirtQemuKernel.dsc     | 11 +++++++++++
> >   3 files changed, 27 insertions(+)
> >
> > diff --git a/ArmVirtPkg/ArmVirtQemu.dsc b/ArmVirtPkg/ArmVirtQemu.dsc
> > index f77443229e8e..1771ad562225 100644
> > --- a/ArmVirtPkg/ArmVirtQemu.dsc
> > +++ b/ArmVirtPkg/ArmVirtQemu.dsc
> > @@ -140,6 +140,8 @@ [PcdsFeatureFlag.common]
> >
> >     gArmVirtTokenSpaceGuid.PcdTpm2SupportEnabled|$(TPM2_ENABLE)
> >
> > +  gArmTokenSpaceGuid.PcdMonitorConduitHvc|TRUE
> > +
>
> It seems that the PSCI conduit needs to be dynamically set.

Why? And how is this different from PSCI for resetting the system?

Note that ArmVIrtQemu was never intended to run at EL2, even if it
seems to work to some extent.


> The psci conduit that should be used is configured by qemu depending on the
> virtualization=[on|off] parameter. When off, HVC must be used (SMC otherwise).
> Cf:
> https://github.com/qemu/qemu/blob/master/hw/arm/virt.c#L2052
>
> If using the wrong conduit, qemu traps the instruction and stops.
> For KvmTool, the conduit is always HVC.
>
> Command used:
> [PATH_TO]/qemu/build/qemu-system-aarch64 \
>         -serial stdio -M virt,highmem=on,virtualization=off \
>         -cpu cortex-a57 -smp 4 -m 4096 \
>         -drive file=pflash0.img,format=raw,if=pflash,readonly=on \
>         -drive file=pflash1.img,format=raw,if=pflash
>
> Regards,
> Pierre
>
>
> 
>
>