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

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Date:   Thu, 12 Jan 2017 08:21:00 +0800
From:   Zhou Wang <wangzhou1@...ilicon.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
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>,
        jorn Helgaas <bhelgaas@...gle.com>, <liudongdong3@...wei.com>,
        <gabriele.paoloni@...wei.com>, <xuwei5@...ilicon.com>,
        <linux-acpi@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI/PCI: Fix bus range comparation in pci_mcfg_lookup

On 2017/1/12 5:37, Bjorn Helgaas wrote:
> On Wed, Jan 04, 2017 at 03:00:06PM +0800, 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>
> 
> Applied to pci/enumeration for v4.11 with the following changelog:
> 
>     PCI/ACPI: Fix bus range comparison in pci_mcfg_lookup()
>     
>     The configuration data provided by an MCFG entry, i.e., PCI segment and bus
>     range, may span multiple host bridges.
>     
>     pci_mcfg_lookup() previously required an exact match of the host bridge
>     starting bus and the MCFG starting bus, which made the following
>     configuration fail:
>     
>       MCFG region:
>         segment: 0
>         bus range: 0x00-0xff
>     
>       host bridge
>         segment: 0
>         bus range: 0x20-0x4f
>     
>     Relax the bus range check in pci_mcfg_lookup() so we can use any MCFG entry
>     that contains the required bus range, as we do in pci_mmconfig_lookup().
>     
>     [bhelgaas: changelog]
>     Signed-off-by: Zhou Wang <wangzhou1@...ilicon.com>
>     Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
>     Reviewed-by: Tomasz Nowicki <tn@...ihalf.com>
>     Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
>

Hi Bjorn,

Many thanks for modifying the commit message and merging this patch!

Best regards,
Zhou

>> ---
>>  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;
>>  		}
>> -- 
>> 1.9.1
>>
>> --
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> 
> .
>