[v3,1/2] x86/PCI: Fix a potential regression when use dmi_get_bios_year()

dmi_get_bios_year() may return 0 when it is incapable to parse
the BIOS date string. Previously this has been checked in
pci_acpi_crs_quirks().

Update the code to restore old behaviour.

Reported-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 arch/x86/pci/acpi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Hi Andy,

On Tue, 20 Mar 2018 15:54:09 +0200, Andy Shevchenko wrote:
> dmi_get_bios_year() may return 0 when it is incapable to parse
> the BIOS date string. Previously this has been checked in
> pci_acpi_crs_quirks().
> 
> Update the code to restore old behaviour.

When fixing a regression, a good practice is to tag the fix commit as
such:

Fixes: 69c42d493db4 ("x86/pci: Simplify code by using the new dmi_get_bios_year() helper")

> Reported-by: Jean Delvare <jdelvare@suse.de>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>  arch/x86/pci/acpi.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
> index 00e60de30328..5559dcaddd5e 100644
> --- a/arch/x86/pci/acpi.c
> +++ b/arch/x86/pci/acpi.c
> @@ -140,7 +140,9 @@ static const struct dmi_system_id pci_crs_quirks[] __initconst = {
>  
>  void __init pci_acpi_crs_quirks(void)
>  {
> -	if ((dmi_get_bios_year() < 2008) && (iomem_resource.end <= 0xffffffff))
> +	int year = dmi_get_bios_year();
> +
> +	if (year >= 0 && year < 2008 && iomem_resource.end <= 0xffffffff)
>  		pci_use_crs = false;
>  
>  	dmi_check_system(pci_crs_quirks);

This works with the non-inline version of dmi_get_bios_year()
introduced by patch 2/2 of this series. However the inline version of
this function would return 0 on error, which makes the condition above
always true.

The patches need to be applied in the opposite order, or the test above
should be changed to "year > 0".

Reviewed-by: Jean Delvare <jdelvare@suse.de>

On Tue, 2018-03-20 at 16:32 +0100, Jean Delvare wrote:
> Hi Andy,
> 
> On Tue, 20 Mar 2018 15:54:09 +0200, Andy Shevchenko wrote:
> > dmi_get_bios_year() may return 0 when it is incapable to parse
> > the BIOS date string. Previously this has been checked in
> > pci_acpi_crs_quirks().
> > 
> > Update the code to restore old behaviour.
> 
> When fixing a regression, a good practice is to tag the fix commit as
> such:
> 
> Fixes: 69c42d493db4 ("x86/pci: Simplify code by using the new
> dmi_get_bios_year() helper")

Someone (perhaps Ingo) told me that Fixes doesn't make much sense if the
fixing commit is not yet in vanilla.

Since it's supposed to go via tip tree I would like to hear Ingo's
opinion before adding this line to the patch.

> > Reported-by: Jean Delvare <jdelvare@suse.de>
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > ---
> >  arch/x86/pci/acpi.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
> > index 00e60de30328..5559dcaddd5e 100644
> > --- a/arch/x86/pci/acpi.c
> > +++ b/arch/x86/pci/acpi.c
> > @@ -140,7 +140,9 @@ static const struct dmi_system_id
> > pci_crs_quirks[] __initconst = {
> >  
> >  void __init pci_acpi_crs_quirks(void)
> >  {
> > -	if ((dmi_get_bios_year() < 2008) && (iomem_resource.end <=
> > 0xffffffff))
> > +	int year = dmi_get_bios_year();
> > +
> > +	if (year >= 0 && year < 2008 && iomem_resource.end <=
> > 0xffffffff)
> >  		pci_use_crs = false;
> >  
> >  	dmi_check_system(pci_crs_quirks);
> 
> This works with the non-inline version of dmi_get_bios_year()
> introduced by patch 2/2 of this series. However the inline version of
> this function would return 0 on error, which makes the condition above
> always true.
> 
> The patches need to be applied in the opposite order, or the test
> above
> should be changed to "year > 0".

Err... Yes, I use to have them in opposite order, but at some point I
decided to reverse and forgot about the condition.

So, you are right, it needs to be applied in reversed order.

> 
> Reviewed-by: Jean Delvare <jdelvare@suse.de>
>

On Tue, 20 Mar 2018, Andy Shevchenko wrote:
> On Tue, 2018-03-20 at 16:32 +0100, Jean Delvare wrote:
> > Hi Andy,
> > 
> > On Tue, 20 Mar 2018 15:54:09 +0200, Andy Shevchenko wrote:
> > > dmi_get_bios_year() may return 0 when it is incapable to parse
> > > the BIOS date string. Previously this has been checked in
> > > pci_acpi_crs_quirks().
> > > 
> > > Update the code to restore old behaviour.
> > 
> > When fixing a regression, a good practice is to tag the fix commit as
> > such:
> > 
> > Fixes: 69c42d493db4 ("x86/pci: Simplify code by using the new
> > dmi_get_bios_year() helper")
> 
> Someone (perhaps Ingo) told me that Fixes doesn't make much sense if the
> fixing commit is not yet in vanilla.

No. If the commit is already queued for the next merge window then a fixes
tag is appropriate.

Thanks,

	tglx

On Tuesday, March 20, 2018 2:54:09 PM CET Andy Shevchenko wrote:
> dmi_get_bios_year() may return 0 when it is incapable to parse
> the BIOS date string. Previously this has been checked in
> pci_acpi_crs_quirks().
> 
> Update the code to restore old behaviour.
> 
> Reported-by: Jean Delvare <jdelvare@suse.de>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>  arch/x86/pci/acpi.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
> index 00e60de30328..5559dcaddd5e 100644
> --- a/arch/x86/pci/acpi.c
> +++ b/arch/x86/pci/acpi.c
> @@ -140,7 +140,9 @@ static const struct dmi_system_id pci_crs_quirks[] __initconst = {
>  
>  void __init pci_acpi_crs_quirks(void)
>  {
> -	if ((dmi_get_bios_year() < 2008) && (iomem_resource.end <= 0xffffffff))
> +	int year = dmi_get_bios_year();
> +
> +	if (year >= 0 && year < 2008 && iomem_resource.end <= 0xffffffff)
>  		pci_use_crs = false;
>  
>  	dmi_check_system(pci_crs_quirks);
> 

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

On Tue, 2018-03-20 at 17:47 +0100, Thomas Gleixner wrote:
> On Tue, 20 Mar 2018, Andy Shevchenko wrote:
> > On Tue, 2018-03-20 at 16:32 +0100, Jean Delvare wrote:

> > > When fixing a regression, a good practice is to tag the fix commit
> > > as
> > > such:
> > > 
> > > Fixes: 69c42d493db4 ("x86/pci: Simplify code by using the new
> > > dmi_get_bios_year() helper")
> > 
> > Someone (perhaps Ingo) told me that Fixes doesn't make much sense if
> > the
> > fixing commit is not yet in vanilla.
> 
> No. If the commit is already queued for the next merge window then a
> fixes
> tag is appropriate.

Thank you, Thomas, for clarification.
Will do this in v4.

On Tue, 20 Mar 2018 17:47:41 +0100 (CET), Thomas Gleixner wrote:
> On Tue, 20 Mar 2018, Andy Shevchenko wrote:
> > On Tue, 2018-03-20 at 16:32 +0100, Jean Delvare wrote:  
> > > When fixing a regression, a good practice is to tag the fix commit as
> > > such:
> > > 
> > > Fixes: 69c42d493db4 ("x86/pci: Simplify code by using the new
> > > dmi_get_bios_year() helper")  
> > 
> > Someone (perhaps Ingo) told me that Fixes doesn't make much sense if the
> > fixing commit is not yet in vanilla.  
> 
> No. If the commit is already queued for the next merge window then a fixes
> tag is appropriate.

+1

Even if it won't be used for stable branches, it's still valuable for
distribution kernel maintainers to find out the fixes to patches they
backport.

Thanks,