linux-kernel - Re: [Debug 2/2] x86/PCI/ACPI: Relax ACPI resource descriptor checks to work around BIOS bugs

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Date:	Tue, 3 Mar 2015 09:18:03 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Jiang Liu <jiang.liu@...ux.intel.com>
Cc:	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	Thomas Voegtle <tv@...96.de>, Hudd <hedede.l@...il.com>,
	Prakash Punnoor <prakash@...noor.de>,
	Francois Romieu <romieu@...zoreil.com>,
	Dave Airlie <airlied@...il.com>,
	Marcel Holtmann <marcel@...tmann.org>,
	Len Brown <lenb@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Lv Zheng <lv.zheng@...el.com>
Subject: Re: [Debug 2/2] x86/PCI/ACPI: Relax ACPI resource descriptor checks
 to work around BIOS bugs

On Mon, Mar 2, 2015 at 10:25 PM, Jiang Liu <jiang.liu@...ux.intel.com> wrote:
> Some BIOSes report incorrect length for ACPI address space descriptors,
> so relax the checks to avoid regressions.
>
> Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>

It'd be nice to have a DSDT archived and referenced in this changelog
for future reference.  This sounds similar to previous issues:

3162b6f0c5e1 ("PNPACPI: truncate _CRS windows with _LEN > _MAX - _MIN + 1")
d558b483d5a7 ("x86/PCI: truncate _CRS windows with _LEN > _MAX - _MIN + 1")
f238b414a74a ("PNPACPI: compute Address Space length rather than using _LEN")
48728e077480 ("x86/PCI: compute Address Space length rather than using _LEN")

I assume your work fixes both these paths and avoids the issues we fixed above.

> ---
>  drivers/acpi/resource.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/resource.c b/drivers/acpi/resource.c
> index c723668e3e27..5589a6e2a023 100644
> --- a/drivers/acpi/resource.c
> +++ b/drivers/acpi/resource.c
> @@ -42,8 +42,10 @@ static bool acpi_dev_resource_len_valid(u64 start, u64 end, u64 len, bool io)
>          * CHECKME: len might be required to check versus a minimum
>          * length as well. 1 for io is fine, but for memory it does
>          * not make any sense at all.
> +        * Note: some BIOSes report incorrect length for ACPI address space
> +        * descriptor, so remove check of 'reslen == len' to avoid regression.
>          */
> -       if (len && reslen && reslen == len && start <= end)
> +       if (len && reslen && start <= end)
>                 return true;
>
>         pr_debug("ACPI: invalid or unassigned resource %s [%016llx - %016llx] length [%016llx]\n",
> --
> 1.7.10.4
>
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