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SubjectRe: [PATCH] pci, add FW_BUG warning to pci= kernel option
[+cc lkml, linux-arch, Linus]

On Sat, Nov 01, 2014 at 02:11:19PM -0400, Prarit Bhargava wrote:
> The kernel should boot PCI without the use of kernel parameters. Display
> a FW_BUG warning when pci= is used.
>
> Cc: Myron Stowe <mstowe@redhat.com>
> Cc: linux-pci@vger.kernel.org
> Signed-off-by: Prarit Bhargava <prarit@redhat.com>
> ---
> drivers/pci/pci.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 625a4ac..5172060b 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4515,6 +4515,8 @@ static int __init pci_setup(char *str)
> }
> str = k;
> }
> + add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
> + pr_crit(FW_BUG "The PCI configuration has been overridden thorugh the use of pci=. Please report the issue you are attempting to resolve to your hardware vendor.\n");

My goal is to be able to boot without any "pci=" parameters, so from that
perspective, I like this.

When people have a problem booting Linux, they often try a variety of
things like "pci=assign-busses", "pci=nocrs", "pci=nomsi", "pci=nommconf",
"pci=noacpi", etc. If they find something that works, there's a tendency
to treat that as a "solution." I'd rather that they report it, so we can
try to fix the bug or add a quirk so the *next* person won't have to figure
out the right parameters to use.

My worry is that there are a few things where Linux isn't smart enough to
do the right thing automatically, and I don't think we'll have a good
solution in the near future. For example:

pci=norom
pci=pcie_bus_perf,pcie_bus_safe,etc.
pci=cbiosize=...
pci=cbmemsize=...
pci=resource_alignment=...
pci=hpiosize=...
pci=hpmemsize=...
pci=realloc

I don't like the fact that these options exist, but I suspect there are
users that do depend on them and might find this warning too aggressive.

So I'm interested in opinions on whether this is a good idea at all and
whether we should exclude some options from the warning/tainting.

Bjorn

> return 0;
> }
> early_param("pci", pci_setup);
> --
> 1.7.9.3
>
> --
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