linux-kernel - Re: [PATCH] ACPI/PCI: Fix bus range comparation in pci_mcfg

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Date:   Wed, 11 Jan 2017 08:36:13 +0800
From:   Zhou Wang <wangzhou1@...ilicon.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
CC:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, Tomasz Nowicki <tn@...ihalf.com>,
        Jayachandran C <jchandra@...adcom.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Dongdong Liu <liudongdong3@...wei.com>,
        Gabriele Paoloni <gabriele.paoloni@...wei.com>,
        <xuwei5@...ilicon.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI/PCI: Fix bus range comparation in pci_mcfg_lookup

On 2017/1/10 5:45, Rafael J. Wysocki wrote:
> On Mon, Jan 9, 2017 at 4:39 AM, Zhou Wang <wangzhou1@...ilicon.com> wrote:
>> On 2017/1/4 15:00, Zhou Wang wrote:
>>> The configuration data provided by an MCFG region (ie PCI segment and
>>> bus range) may span multiple host bridges.
>>>
>>> Current code in pci_mcfg_lookup() carries out an exact match of host
>>> bridge bus range start value against the MCFG region(s) bus range start
>>> value which would cause configurations like the following:
>>>
>>> MCFG region:
>>>       bus range: 0x00~0xff.
>>>       segment: 0.
>>>
>>> PCI host bridges configuration (segment numbers and bus ranges):
>>>       host bridge 1:
>>>               bus range: 0x00~0x1f.
>>>               segment: 0.
>>>       host bridge 2:
>>>               bus range: 0x20~0x4f.
>>>               segment: 0.
>>>
>>> to fail, in that the bus range start value for host bridge 2 does
>>> not match the bus range start value of the respective MCFG region.
>>>
>>> Relax the bus range check in pci_mcfg_lookup() to cater for
>>> PCI configurations with multiple host bridges sharing the same
>>> MCFG region.
>>>
>>> Signed-off-by: Zhou Wang <wangzhou1@...ilicon.com>
>>> Reviewed-by: Tomasz Nowicki <tn@...ihalf.com>
>>> Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
>>> ---
>>>  drivers/acpi/pci_mcfg.c | 5 ++---
>>>  1 file changed, 2 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c
>>> index a6a4cea..2944353 100644
>>> --- a/drivers/acpi/pci_mcfg.c
>>> +++ b/drivers/acpi/pci_mcfg.c
>>> @@ -195,11 +195,10 @@ int pci_mcfg_lookup(struct acpi_pci_root *root, struct resource *cfgres,
>>>               goto skip_lookup;
>>>
>>>       /*
>>> -      * We expect exact match, unless MCFG entry end bus covers more than
>>> -      * specified by caller.
>>> +      * We expect the range in bus_res in the coverage of MCFG bus range.
>>>        */
>>>       list_for_each_entry(e, &pci_mcfg_list, list) {
>>> -             if (e->segment == seg && e->bus_start == bus_res->start &&
>>> +             if (e->segment == seg && e->bus_start <= bus_res->start &&
>>>                   e->bus_end >= bus_res->end) {
>>>                       root->mcfg_addr = e->addr;
>>>               }
>>>
>>
>> Hi Rafael,
>>
>> Could you please look into this patch if you have time?
> 
> Well, it makes sense to me, but this is PCI, so Bjorn has to decide here.
> 
> Thanks,
> Rafael

Many thanks for looking into this patch!

Hi Bjorn,

Please look at this patch if you have time :)

Thanks,
Zhou

> 
> .
>