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 22/10/2015 20:04, Kevin O'Connor wrote:
> On Thu, Oct 22, 2015 at 10:40:08AM +0200, Paolo Bonzini wrote:
>> On 21/10/2015 20:36, Jordan Justen wrote:
>>> On 2015-10-20 11:14:00, Laszlo Ersek wrote:
>>>> Commit 4d00636e97b7 ("ich9: Add the lpc chip", Nov 14 2012) added the
>>>> ich9_apm_ctrl_changed() ioport write callback function such that it would
>>>> inject the SMI, in response to a write to the APM_CNT register, on the
>>>> first CPU, invariably.
>>>>
>>>> Since this register is used by guest code to trigger an SMI synchronously,
>>>> the interrupt should be injected on the VCPU that is performing the write.
>>>
>>> Why not send an SMI to *all* processors, like the real chipsets do?
>>
>> That's much less scalable, and more important I would have to check that
>> SeaBIOS can handle that correctly.  It probably doesn't, as it doesn't
>> relocate SMBASEs.
> 
> SeaBIOS is only expecting its SMI handler to be called once in
> response to a synchronous SMI.  We can change SeaBIOS to fix that.
> 
> SeaBIOS does relocate the smbase from 0x30000 to 0xa0000 during its
> init phase (by creating a synchronous SMI on the BSP and then setting
> the smbase register to 0xa0000 in the smi handler).

Right; however it would also have to relocate the SMBASE on the APs (in
case they were halted with cli;hlt and not INITed).  It's really not
worth the hassle, it's not even documented in the chipset docs whether
0xb2 sends an SMI to all processors or only the running one.

Paolo