Re: [PATCH] hw/ppc/Kconfig: NVDIMM is a hard requirement for the pseries machine

[Daniel Henrique Barboza]

On 5/4/23 15:05, Thomas Huth wrote:
> When building QEMU with "--without-default-devices", the pseries
> machine fails to start even when running with the --nodefaults option:
>
>   $ ./qemu-system-ppc64 --nodefaults -M pseries
>   Type 'spapr-nvdimm' is missing its parent 'nvdimm'
>   Aborted (core dumped)
>
> Looks like NVDIMM is a hard requirement for this machine nowadays.

Ouch.

I believe this has to do with this comment in hw/ppc/spapr.c, in
spapr_instance_init():

    /*
     * NVDIMM support went live in 5.1 without considering that, in
     * other archs, the user needs to enable NVDIMM support with the
     * 'nvdimm' machine option and the default behavior is NVDIMM
     * support disabled. It is too late to roll back to the standard
     * behavior without breaking 5.1 guests.
     */
    if (mc->nvdimm_supported) {
        ms->nvdimms_state->is_enabled = true;
    }

It seems like you found out another side effect of this nvdimm situation that 
Igor
documented 2 years ago in 55810e90 ("ppc/spapr: cleanup -machine 
pseries,nvdimm=X
handling").


Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>


I'll send a PPC PR in the next few days. Let me know if you want me to queue it.


Thanks,


Daniel

> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>   hw/ppc/Kconfig | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/ppc/Kconfig b/hw/ppc/Kconfig
> index c898021b5f..a689d9b219 100644
> --- a/hw/ppc/Kconfig
> +++ b/hw/ppc/Kconfig
> @@ -3,7 +3,7 @@ config PSERIES
>       imply PCI_DEVICES
>       imply TEST_DEVICES
>       imply VIRTIO_VGA
> -    imply NVDIMM
> +    select NVDIMM
>       select DIMM
>       select PCI
>       select SPAPR_VSCSI