[SeaBIOS] [PATCH 3/3] Take in account hot(un)plugged cpus on reboot

[Gleb Natapov]

On Tue, Mar 13, 2012 at 10:37:54AM +0100, Igor Mammedov wrote:
> On 03/13/2012 01:09 AM, Kevin O'Connor wrote:
> >On Sat, Mar 10, 2012 at 12:47:28PM +0100, Igor Mammedov wrote:
> >>Initial count of active cpus is communicated to bios from qemu via
> >>CMOS_BIOS_SMP_COUNT io port. However if cpus are hotplugged after
> >>boot and then guest is rebooted without taking down qemu then
> >>bios might be stuck at smp_probe
> >[...]
> >>--- a/src/smp.c
> >>+++ b/src/smp.c
> >>@@ -17,6 +17,9 @@
> >>
> >>  #define APIC_ENABLED 0x0100
> >>
> >>+#define ACPI_CPU_STATUS_MAP 0xaf00
> >>+#define ACPI_CPU_STATUS_MAP_SZ 32
> >>+
> >>  struct { u32 ecx, eax, edx; } smp_mtrr[32] VAR16VISIBLE;
> >>  u32 smp_mtrr_count VAR16VISIBLE;
> >>
> >>@@ -115,6 +118,26 @@ smp_probe(void)
> >>          msleep(10);
> >>      } else {
> >>          u8 cmos_smp_count = inb_cmos(CMOS_BIOS_SMP_COUNT);
> >>+        dprintf(1, "Powered-on with %d cpu(s)\n", cmos_smp_count + 1);
> >>+
> >>+        if (qemu_cfg_have_acpi_cpus_map()) {
> >[...]
> >
> >Please don't clutter up smp.c with this.  The code should look
> >something like:
> >
> >           int total_cpus = getCPUcount();
> >           while (readl(&CountCPUs)<  total_cpus)
> >               yield();
> >
> >The getCPUcount() can be buried in paravirt.c, acpi.c, or where ever
> >it makes sense.
> 
> Thanks Kevin,
> I'll amend and repost patch-set taking in account your suggestions.
> 
> >BTW, why do we have to call qemu_cfg_have_acpi_cpus_map?  Can't this
> >just be inferred if the data at inb(0xaf00) is all zeros?
We can't rely on the fact that unused port returns all zeros. Actually
on real HW I think it return all ones.

> What if qemu doesn't have 0xaf00 (like current upstream)?
> cfg_have_acpi_cpus_map is just a flag that allows to detect if qemu
> provides 0xaf00. This way it would be possible for seabios to work with
> old and new versions of qemu without breaking anything.
> 
If QEMU will update cmos cpu count on cpu (un)plug we will not have to
introduce new PV interface to telll SeaBIOS about 0xaf00.

--
			Gleb.