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

[Gleb Natapov]

On Tue, Mar 13, 2012 at 11:16:51AM +0100, Igor Mammedov wrote:
> 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.
> 
Good point. You mean we need a list of apic ids of available cpus right?
Can SeaBIOS build this list by reading apic id in smp_ap_boot_code?

--
			Gleb.