Re: [Qemu-devel] [PATCH] hw/isa/lpc_ich9: inject the SMI on the VCPU that is writing to APM_CNT

[Paolo Bonzini <pbonzini@redhat.com>]

On 23/10/2015 20:20, Jordan Justen wrote:
>>>> It's not worth the hassle to relocate the SMBASE of the APs?
>>>> So, basically, write to 0x30000-0x38000, then send an SMI IPI to the
>>>> AP and now you have the AP running in SMI and it has extra privileges?
>>>
>>> Extra privileges compared to what?  Legacy BIOS does not really put
>>> anything privileged in SMRAM,
> 
> Why does seabios even bother relocating the BSP's SMBASE if it doesn't
> relocate the SMBASE for the APs?

It uses SMM to run INT 13h in 32-bit real mode, basically.  It's for
MS-DOS usage only, so the APs don't matter.

>> So what are we thinking about a magic APM_STS value to trigger an SMI
>> for all VCPUs? 0x51 ('Q') would be cool. :)
> 
> This seems like a further deviation from the actual hardware. I
> understand that QEMU draws a line about strict hardware emulation, but
> I just wanted to point out the discrepancy.

Yeah, I am also a bit doubtful about that.

> So, the trouble with changing QEMU to better emulate the hardware is
> that seabios can't handle multiple processors entering SMM?

Yes.

Paolo