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From: Shannon Zhao <zhaoshenglong@huawei.com>
To: Peter Maydell <peter.maydell@linaro.org>,
	Shannon Zhao <shannon.zhao@linaro.org>
Cc: edk2-devel@ml01.01.org, qemu-arm <qemu-arm@nongnu.org>,
	Laszlo Ersek <lersek@redhat.com>,
	QEMU Developers <qemu-devel@nongnu.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>
Subject: Re: [Qemu-devel] [PATCH] ARM: Virt: Don't generate RTC ACPI node when using UEFI
Date: Wed, 13 Jan 2016 09:50:14 +0800	[thread overview]
Message-ID: <5695AD56.2040402@huawei.com> (raw)
In-Reply-To: <CAFEAcA-=9h11a2AvJYBNzfeDsW7-KS7x_7N-T0udr6NZ9Gu9bg@mail.gmail.com>



On 2016/1/12 23:30, Peter Maydell wrote:
> On 12 January 2016 at 15:24, Shannon Zhao <shannon.zhao@linaro.org> 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/edk2-devel@lists.01.org/msg06301.html

Thanks,
-- 
Shannon

  reply	other threads:[~2016-01-13  1:54 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-12 15:24 [Qemu-devel] [PATCH] ARM: Virt: Don't generate RTC ACPI node when using UEFI Shannon Zhao
2016-01-12 15:30 ` Peter Maydell
2016-01-13  1:50   ` Shannon Zhao [this message]
2016-01-13 10:09   ` Laszlo Ersek
2016-01-13 10:18 ` Laszlo Ersek
2016-01-13 10:20   ` Ard Biesheuvel
2016-01-13 10:48     ` Laszlo Ersek
2016-01-13 11:52       ` Peter Maydell

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