[+cc Bob for spec typo question]
On Wed, Mar 27, 2013 at 10:28 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
> Found problem on system that firmware that could handle pci aer.
> Firmware get error reporting after pci injecting error, before os boots.
> But after os boots, firmware can not get report anymore, even pci=noaer
> is passed.
>
> Root cause: BIOS _OSC has problem with query bit checking.
> It turns out that BIOS vendor is copying example code from ACPI Spec.
> In ACPI Spec 5.0, page 290:
>
> If (Not(And(CDW1,1))) // Query flag clear?
> { // Disable GPEs for features granted native control.
> If (And(CTRL,0x01)) // Hot plug control granted?
> {
> Store(0,HPCE) // clear the hot plug SCI enable bit
> Store(1,HPCS) // clear the hot plug SCI status bit
> }
> ...
> }
>
> When Query flag is set, And(CDW1,1) will be 1, Not(1) will return 0xfffffffe.
> So it will get into code path that should be for control set only.
> BIOS acpi code should be changed to "If (LEqual(And(CDW1,1), 0)))"
Isn't this just a typo in the spec? Shouldn't it be using "LNot"
instead of "Not"?
If (LNot(And(CDW1,1))) // Query flag clear?
Of course, that doesn't change the need for your Linux change, though
a comment about the hazard might be nice for future readers.
> Current kernel code is using _OSC query to notify firmware about support
> from OS and then use _OSC to set control bits.
> During query support, current code is using all possible controls.
> So will execute code that should be only for control set stage.
>
> That will have problem when pci=noaer or aer firmware_first is used.
> As firmware have that control set for os aer already in query support stage,
> but later will not os aer handling.
>
> We should avoid passing all possible controls, just use osc_control_set
> instead.
> That should workaround BIOS bugs with affected systems on the field
> as more bios vendors are copying sample code from ACPI spec.
>
> Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxx
>
> ---
> drivers/acpi/pci_root.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> Index: linux-2.6/drivers/acpi/pci_root.c
> ===================================================================
> --- linux-2.6.orig/drivers/acpi/pci_root.c
> +++ linux-2.6/drivers/acpi/pci_root.c
> @@ -201,8 +201,8 @@ static acpi_status acpi_pci_query_osc(st
> *control &= OSC_PCI_CONTROL_MASKS;
> capbuf[OSC_CONTROL_TYPE] = *control | root->osc_control_set;
> } else {
> - /* Run _OSC query for all possible controls. */
> - capbuf[OSC_CONTROL_TYPE] = OSC_PCI_CONTROL_MASKS;
> + /* Run _OSC query only with existing controls. */
> + capbuf[OSC_CONTROL_TYPE] = root->osc_control_set;
> }
>
> status = acpi_pci_run_osc(root->device->handle, capbuf, &result);
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