Re: [Qemu-devel] [PATCH V11 0/8] add pvpanic mmio support

[<peng.hao2@zte.com.cn>]

>On Mon, 3 Dec 2018 at 11:04, Peng Hao <peng.hao2@zte.com.cn> wrote:
>>
>> The first patches are simple cleanups:
>>      - patch 1 move the pvpanic device with the 'ocmmon objects' so we compile
>>                it once for the x86/arm/aarch64 archs,
>>      - patch 2 simply renames ISA fields/definitions to generic ones.
>>
>>      Then instead of add/use the MMIO pvpanic device in the virt machine in an
>>      unique patch, I split it in two distinct patches:
>>      - patch 3 uses Peng Hao's work, but add the MMIO interface to the existing
>>         device (no logical change).
>>      - patch 4 is Peng Hao's work in the virt machine (no logical change).
>>      - patch 5 add pvpanic device in acpi table in virt machine
>>      v2 from Peng Hao is:
>>      https://lists.gnu.org/archive/html/qemu-devel/2018-10/msg03433.html
>
>I would still prefer to see a more detailed examination of whether
>we can do this with a PCI device before we commit to taking the
>MMIO version into the virt board.

I'm sorry I thought I had sent an email. yesterday when I wrote an email to 
explain the reason, I was interrupted and forgot to send it out.

Now the pvpanic device is implemented as a mmio device or an ACPI device in the kernel, 
and only one device can be seen at the same time. If the kernel parses FDT first, then pvpanic  
is a mmio device. The kernel parses ACPI table first(and virtual machine is configured with ACPI), 
and pvpanic  is an ACPI device.
If pvpanic is implemented as a PCI device, then the PCI device must still be seen when the ACPI table 
is first parsed by the kernel, because ACPI device relies on the mmio space of the PCI device.
Mmio devices can be thought of as just an address space rather than a device in the strict sense.

Secondly, I don't want it to be a pluggable device. If the user deletes the device by mistake, it may lead to unpredictable results.

thanks.
>thanks
>-- PMM