Re: [Qemu-devel] [PATCH] ARM: Virt: Don't generate RTC ACPI node when using UEFI

[Shannon Zhao]

On 2016/1/12 23:30, Peter Maydell wrote:
> On 12 January 2016 at 15:24, Shannon Zhao <address@hidden> wrote:
>> > When booting VM through UEFI, UEFI takes ownership of the RTC hardware.
>> > To DTB UEFI could call libfdt api to disable the RTC device node, but to
>> > ACPI it couldn't do that. Therefore, we don't generate the RTC ACPI
>> > device in QEMU when using UEFI.
> I don't really understand this. I thought that if we were
> using ACPI then we would always be doing it via UEFI?
> 
Currently this is true and maybe for a long time this is also true.

> Also I think if UEFI wants to take command of some of the
> hardware it ought to be UEFI's job to adjust the tables
> accordingly before it passes them on to the guest OS.
Yes, the ideal method is adjusting the DSDT table in UEFI. But there is
almost no way to parse the DSDT table in UEFI. If we want to support
that it will introduce ACPI interpreter. This makes it more complex.

There is a discussion [1] about this on the edk2 list.

[1]https://www.mail-archive.com/address@hidden/msg06301.html

Thanks,
-- 
Shannon