Re: [PATCH v2] pc: add property for Linux setup_data random number seed

[Paolo Bonzini]

On 8/5/22 09:01, Michael S. Tsirkin wrote:
> > -    if (!legacy_no_rng_seed) {
> > +    if (x86ms->linuxboot_randomness != ON_OFF_AUTO_OFF &&
> > +        (protocol >= 0x209 || x86ms->linuxboot_randomness == ON_OFF_AUTO_ON)) {
> Hmm so if user requested "on" but protocol is too old then we just
> ignore it silently? I'd rather we failed initialization.
> So:
>
> if (x86ms->linuxboot_randomness == ON_OFF_AUTO_ON &&
>      protocol < 0x209) {
>         fprintf(stderr, "qemu: Linux kernel too old to load a dtb\n");
>         exit(1);
> }

It doesn't ignore the "on" setting; it passes the seed anyway even if 
the protocol is too old.  Basically, a kernel that is too old to support 
setup data is treated the same as a kernel that supports setup data but 
doesn't know about the seed datum.

It seemed the more sensible implementation because anyway you cannot 
know if the kernel will use the datum.

Paolo