Re: [SeaBIOS] [PATCH for-1.10-stable] drop "etc/boot-cpus" fw_cfg file and reuse legacy QEMU_CFG_NB_CPUS

[Igor Mammedov]

On Tue, 15 Nov 2016 09:54:47 -0500
"Kevin O'Connor"  wrote:
> On Fri, Nov 11, 2016 at 04:35:15PM +0100, Igor Mammedov wrote:
> > since QEMU_CFG_NB_CPUS not going away anytime soon
> > and serves the same purpose as just added "etc/boot-cpus" fw_cfg
> > drop support for "etc/boot-cpus" while this code is not
> > in use yet (i.e. QEMU with "etc/boot-cpus" hasn't been released)
> > and reuse QEMU_CFG_NB_CPUS instead of it.
>
> [...]
> > u16
> >  qemu_get_present_cpus_count(void)
> >  {
> > u16 smp_count;
> > if (!boot_cpus_file_sz) {
> >    smp_count = rtc_read(CMOS_BIOS_SMP_COUNT) + 1;
> > } else {
> >    qemu_cfg_read_entry(&smp_count, boot_cpus_sel, boot_cpus_file_sz);
> > u16 smp_count = 0;
> > qemu_cfg_read_entry(&smp_count, QEMU_CFG_NB_CPUS, sizeof smp_count);
> > u16 cmos_cpu_count = rtc_read(CMOS_BIOS_SMP_COUNT) + 1;
> > if (smp_count < cmos_cpu_count) {
> >    smp_count = cmos_cpu_count;
> > }
> >    return smp_count;
> >
> > }
>
> Just to confirm the forwards and backwards compatibility here - if the
> above SeaBIOS code runs on QEMU version pre-2.8 then cmos_cpu_count
> will always be greater than or equal to QEMU_CFG_NB_CPUS, and if
> SeaBIOS runs on QEMU >= v2.8 then QEMU_CFG_NB_CPUS will always be
> greater than or equal to cmos_cpu_count?

yep
> -Kevin
>
> P.S. minor nit, but I prefer sizeof treated as a function (ie,
> sizeof(smp_count) ), but I can fixup on commit.

Thanks, I'll try to remember.