Re: [Qemu-devel] [PATCH] target-i386: Initialize CPUState::halted in cpu_reset

[Blue Swirl <blauwirbel@gmail.com>]

On Tue, Apr 26, 2011 at 9:55 PM, Jan Kiszka <jan.kiszka@web.de> wrote:
> On 2011-04-26 20:00, Blue Swirl wrote:
>> On Tue, Apr 26, 2011 at 11:50 AM, Jan Kiszka <jan.kiszka@siemens.com> wrote:
>>> Instead of having an extra reset function at machine level and special
>>> code for processing INIT, move the initialization of halted into the
>>> cpu reset handler.
>>
>> Nack. A CPU is designated as a BSP at board level. CPUs do not need to
>> know about this at all.
>
> That's why we have cpu_is_bsp() in pc.c.
>
> Obviously, every CPU (which includes the APIC) must know if it is
> supposed to be BP or AP. It would be unable to enter the right state
> after reset otherwise (e.g. Intel SDM 9.1). cpu_is_bsp() is basically
> reporting the result of the MP init protocol in condensed from.

Intel 64 and IA-32 Architectures Software Developer’s Manual vol 3A,
7.5.1 says that the protocol result is stored in APIC MSR. I think we
should be using that instead. For example, the board could call
cpu_designate_bsp() to set the BSP flag in MSR. Then cpu_is_bsp()
would only check the MSR, which naturally belongs to the CPU/APIC
domain.