linux-kernel - Re: [PATCH] x86: update mptable v7

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Date:	Wed, 18 Jun 2008 22:11:08 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"Len Brown" <lenb@...nel.org>, "Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: update mptable v7

On Wed, Jun 18, 2008 at 9:32 PM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
> "Yinghai Lu" <yhlu.kernel@...il.com> writes:
>
>> On Wed, Jun 18, 2008 at 5:33 PM, Len Brown <lenb@...nel.org> wrote:
>>>
>>>
>>> On Wed, 18 Jun 2008, Yinghai Lu wrote:
>>>
>>>> On Wed, Jun 18, 2008 at 3:18 PM, Len Brown <lenb@...nel.org> wrote:
>>>> >
>>>> >
>>>> > On Sun, 1 Jun 2008, Yinghai Lu wrote:
>>>> >
>>>> >>
>>>> >> make mptable to be consistent to acpi routing, so we could
>>>> >> 1. kexec kernel with acpi=off
>>>> >> 2. workaround BIOS that acpi routing is working, but mptable is not right.
>>>> >> so can use kernel/kexec to start other os that doesn't have good acpi
>> support
>>>> >
>>>> > Is this an effort to boot an ACPI-mode kernel,
>>>> > and then kexec a non-ACPI kernel?
>>>>
>>>> Yes,
>>>
>>> Why is this feature needed?
>>> There are a number of ways that the resulting kernel may fail,
>>> all platform specific.
>>
>> other os still doesn't have update acpi irq routing support. but has
>> broken mptable.
>
> Which is at least in part a reason to go back to the BIOS manufacturer
> and get them to fix their table.
>
> I can see a warning coming from the kernel if these two tables are inconsistent
> though.
>
>>>> > Doing so could confuse the heck out of the platform firmware,
>>>> > which will think that an ACPI-mode kernel is still running.
>>>> >
>>>> > Note that it is a historic artifact, now considered a bug,
>>>> > that ACPI uses the MPS code.  We should be divorcing these
>>>> > two bodies of code rather than mixing them further.
>>>>
>>>> how about adding config option to not compile mptable related info?
>>>
>>> That's the idea.
>>> CONFIG_MPS=n CONFIG_ACPI=y should build and run on
>>> every PC built in this century.
>>>
>>> This was prototyped a long while back, but the
>>> tree has churned so much since then the old
>>> prototype is worthless.
>>
>> will look at it tonight.
>>
>> when EFI is popular, there is no reason to compile mps related stuff
>> in kernel again. esp for 64 bit.
>
> ? EFI has nothing to do with this.  ACPI is popular today and EFI preserves
> EFI.
>
>> BTW, it is funny that Suse still has fallsafe boot entry with acpi=off.
>
> Silly question.  Given that even writing to this table is platform specific.
> Any chance we can do this any a userspace utility writing through /dev/mem
> for the systems that need it?   We can even bundle the utility in the kexec-tools
> package to make it easier to distribute.

interesting, never thought that.

need to call pci_acpi_enable_irq==>mp_config_acpi_gsi in kernel to
save mp_irqs...

also we could use
old kernel kexec second kernel (with this patch and acpi, and uptable)
and then use second kernel to kexec last kernel...

YH
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