Re: [BUG bisected]: apei_hest_parse explosion

From: Rafael J. Wysocki
Date: Fri Feb 22 2013 - 07:23:42 EST

On Friday, February 22, 2013 09:22:15 AM Thomas Gleixner wrote:
> On Fri, 22 Feb 2013, Rafael J. Wysocki wrote:
> > On Friday, February 22, 2013 02:40:58 AM Rafael J. Wysocki wrote:
> > > It looks like the hest_tab memory mapping is unmapped between acpi_hest_init()
> > > and aer_acpi_firmware_first(), but I have no idea what may be responsible for
> > > that.
> > >
> > > And the only relevant difference between now and before the commit above seems
> > > to be the change of the acpi_hest_init() ordering (which now is called earlier).
> >
> > We actually don't really need to do that thing so early, I think. It looks like
> > we only need to make it available early enough for the AER driver to be able to
> > use it, so I wonder if moving the acpi_hest_init() to a separate
> > subsys_initcall() will work around the problem. That is, something like the
> > patch below.
> Yes, that makes the machine boot.

Although for a reason I didn't think about.

> > But even if this helps, I will be wanting to understand what's up here.
> It's very simple. I have "acpi=off" on the command line. With that
> acpi_hest_init is never called, so hest_disable is not set .....

Well, that explains things (and means that acpi=off doesn't really get much
test coverage these days).

> Brilliant stuff that.

The appended patch should fix the breakage too, can you please verify?


From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Subject: ACPI / APEI: Fix crash in apei_hest_parse() for acpi=off

After commit 92ef2a2 (ACPI: Change the ordering of PCI root bridge
driver registrarion), acpi_hest_init() is never called for acpi=off
(acpi_disabled), so hest_disable is not set, but hest_tab is NULL,
which causes apei_hest_parse() to crash when it is called from

Fix that by making apei_hest_parse() check if hest_tab is not NULL
in addition to checking hest_disable. Also remove the now useless
acpi_disabled check from apei_hest_parse().

Reported-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
drivers/acpi/apei/hest.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

Index: test/drivers/acpi/apei/hest.c
--- test.orig/drivers/acpi/apei/hest.c
+++ test/drivers/acpi/apei/hest.c
@@ -89,7 +89,7 @@ int apei_hest_parse(apei_hest_func_t fun
struct acpi_hest_header *hest_hdr;
int i, rc, len;

- if (hest_disable)
+ if (hest_disable || !hest_tab)
return -EINVAL;

hest_hdr = (struct acpi_hest_header *)(hest_tab + 1);
@@ -216,9 +216,6 @@ void __init acpi_hest_init(void)

- if (acpi_disabled)
- goto err;
status = acpi_get_table(ACPI_SIG_HEST, 0,
(struct acpi_table_header **)&hest_tab);
if (status == AE_NOT_FOUND)

I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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