Re: [PATCH] PCI/ACPI: Disable AER when _OSC control bit is clear.

[Rafael J. Wysocki]

On Thu, Jan 11, 2018 at 6:48 PM, Ghannam, Yazen <Yazen.Ghannam@xxxxxxx> wrote:
>> -----Original Message-----
>> From: rjwysocki@xxxxxxxxx [mailto:rjwysocki@xxxxxxxxx] On Behalf Of
>> Rafael J. Wysocki
>> Sent: Thursday, January 11, 2018 12:39 PM
>> To: Ghannam, Yazen <Yazen.Ghannam@xxxxxxx>
>> Cc: ACPI Devel Maling List <linux-acpi@xxxxxxxxxxxxxxx>; Linux Kernel Mailing
>> List <linux-kernel@xxxxxxxxxxxxxxx>; Linux PCI <linux-pci@xxxxxxxxxxxxxxx>;
>> Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>; Len Brown <lenb@xxxxxxxxxx>; Bjorn
>> Helgaas <bhelgaas@xxxxxxxxxx>; Borislav Petkov <bp@xxxxxxx>
>> Subject: Re: [PATCH] PCI/ACPI: Disable AER when _OSC control bit is clear.
>>
>> On Thu, Jan 11, 2018 at 4:03 PM, Yazen Ghannam
>> <Yazen.Ghannam@xxxxxxx> wrote:
>> > From: Yazen Ghannam <yazen.ghannam@xxxxxxx>
>> >
>> > Currently, aer_service_init() checks if AER is available and that
>> > Firmware First handling is not enabled. The _OSC request for AER is
>> > not taken into account when deciding to enable AER in Linux.
>> >
>> > We should check that the _OSC control for AER is set. If it's not
>> > then AER should be disabled.
>> >
>> > The _OSC control for AER is not requested when APEI Firmware First is
>> > used, so the same condition applies.
>> >
>> > Mark AER as disabled if the _OSC request was not made or accepted.
>> >
>> > Remove redunant check for aer_acpi_firmware_first() when calling
>> > aer_service_init(), since this is check is already included when
>> > checking the _OSC control.
>> >
>> > Signed-off-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>
>> > ---
>> >  drivers/acpi/pci_root.c       | 3 +++
>> >  drivers/pci/pcie/aer/aerdrv.c | 2 +-
>> >  2 files changed, 4 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
>> > index 6fc204a52493..19a625ed8de9 100644
>> > --- a/drivers/acpi/pci_root.c
>> > +++ b/drivers/acpi/pci_root.c
>> > @@ -512,6 +512,9 @@ static void negotiate_os_control(struct
>> acpi_pci_root *root, int *no_aspm)
>> >                  */
>> >                 *no_aspm = 1;
>> >         }
>> > +
>> > +       if (!(requested & control & OSC_PCI_EXPRESS_AER_CONTROL))
>>
>> One of the operators above needs to be a && I suppose?
>>
>
> It's a 3-way bitwise AND to check that OSC_PCI_EXPRESS_AER_CONTROL is
> set in both "requested" and "control".
>
> IOW, we check if AER was requested by the OS and that the platform
> granted the request.

OK

I'll queue this up if Bjorn doesn't object, unless Bjorn wants to
apply it himself.

Thanks,
Rafael