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

[Igor Mammedov]

On 03/13/2012 10:51 AM, Gleb Natapov wrote:
> 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.

But we will have to introduce it anyway in future for correct building of
mp/acpi/smbios tables. So why not do it now and be ready later for patches
to mp/acpi/smbios tables.

> --
> 			Gleb.

-- 
-----
  Igor