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

From: peng.hao2
Subject: Re: [Qemu-arm] [PATCH V11 0/8] add pvpanic mmio support
Date: Tue, 4 Dec 2018 08:41:51 +0800 (CST)

>On Mon, 3 Dec 2018 at 11:04, Peng Hao <address@hidden> 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 
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.

>-- PMM

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