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SubjectRe: [PATCH] ACPI/PCI: Fix bus range comparation in pci_mcfg_lookup
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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@hisilicon.com>
>> Reviewed-by: Tomasz Nowicki <tn@semihalf.com>
>> Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.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@hisilicon.com>
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> Reviewed-by: Tomasz Nowicki <tn@semihalf.com>
> Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.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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>
> .
>

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