linux-kernel - Re: [Linaro-acpi] [PATCH v5 0/5] Provide better MADT subtable sanity checks

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Message-ID: <32835486.gnkKHR2R1U@vostro.rjw.lan>
Date:	Mon, 12 Oct 2015 21:25:09 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Sudeep Holla <sudeep.holla@....com>
Cc:	Hanjun Guo <hanjun.guo@...aro.org>, Pat Erley <pat-lkml@...ey.org>,
	Al Stone <ahs3@...hat.com>, linaro-kernel@...ts.linaro.org,
	linux-ia64@...r.kernel.org, patches@...aro.org,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linaro-acpi@...ts.linaro.org, linux-acpi@...r.kernel.org,
	Hanjun Guo <guohanjun@...wei.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [Linaro-acpi] [PATCH v5 0/5] Provide better MADT subtable sanity checks

On Monday, October 12, 2015 10:44:52 AM Sudeep Holla wrote:
> 
> On 12/10/15 08:04, Hanjun Guo wrote:
> > On 10/12/2015 11:58 AM, Pat Erley wrote:
> >> On 10/11/2015 08:49 PM, Hanjun Guo wrote:
> >>> On 10/12/2015 11:08 AM, Pat Erley wrote:
> >>>> On 10/05/2015 10:12 AM, Al Stone wrote:
> >>>>> On 10/05/2015 07:39 AM, Rafael J. Wysocki wrote:
> >>>>>> On Wednesday, September 30, 2015 10:10:16 AM Al Stone wrote:
> >>>>>>> On 09/30/2015 03:00 AM, Hanjun Guo wrote:
> >>>>>>>> On 2015/9/30 7:45, Al Stone wrote:
> >>>>>>>>> NB: this patch set is for use against the linux-pm bleeding edge
> >>>>>>>>> branch.
> >>>>>>>>>
> >>>>>>>
> >>>>>>> [snip...]
> >>>>>>>
> >>>>>>>>
> >>>>>>>> For this patch set,
> >>>>>>>>
> >>>>>>>> Reviewed-by: Hanjun Guo <hanjun.guo@...aro.org>
> >>>>>>>>
> >>>>>>>> Thanks
> >>>>>>>> Hanjun
> >>>>>>>
> >>>>>>> Thanks, Hanjun!
> >>>>>>
> >>>>>> Series applied, thanks!
> >>>>>>
> >>>>>> Rafael
> >>>>>>
> >>>>>
> >>>>> Thanks, Rafael!
> >>>>>
> >>>>
> >>>> Just decided to test out linux-next (to see the new nouveau cleanups).
> >>>> This change set prevents my Lenovo W510 from booting properly.
> >>>>
> >>>> Reverting: 7494b0 "ACPI: add in a bad_madt_entry() function to
> >>>> eventually replace the macro"
> >>>>
> >>>> Gets the system booting again.  I'm attaching my dmesg from the failed
> >>>> boot, who wants the acpidump?
> >>>
> >>> [    0.000000] ACPI: undefined version for either FADT 4.0 or MADT 1
> >>> [    0.000000] ACPI: Error parsing LAPIC address override entry
> >>> [    0.000000] ACPI: Invalid BIOS MADT, disabling ACPI
> >>>
> >>> Seems the MADT revision is not right, could you dump the ACPI MADT
> >>> (APIC) table and send it out? I will take a look :)
> >>>
> >>> Thanks
> >>> Hanjun
> >>
> >> Here ya go, enjoy.  Feel free to CC me on any patches that might fix it.
> >
> > Thanks! I think I had the right guess, the MADT revision is not right
> > for ACPI 4.0:
> >
> > [000h 0000   4]                    Signature : "APIC"    [Multiple APIC
> > Description Table (MADT)]
> > [004h 0004   4]                 Table Length : 000000BC
> > [008h 0008   1]                     *Revision : 01*
> >
> > I encountered such problem before because the table was just copied from
> > previous version, and without the update for table revision.
> >
> > I think we may need to ignore the table revision for x86, but restrict
> > it for ARM64, I'd like Al and Rafael's suggestion before I send out a
> > patch.
> >
> 
> Instead of just removing the check completely on x86, IMO restrict it to
> some newer/later version of ACPI so you can still force vendors to fix
> their ACPI tables at-least in future.

No, we can't force vendors to fix their ACPI tables.  This is completely
unrealistic.

We simly need to deal with the bugs in the ACPI tables in the kernel.

> It would be good to get such sanity check in the tools used to build
> those tables, but yes since such static tables can be built in many
> ways, its difficult to deal it in all those tools.

As I said to Al, we need those checks in firmware test suites.  Having
them in the kernel is OK too, but they should cause warnings to be printed
to the kernel log instead of causing the kernel to panic.

Thanks,
Rafael

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