linux-kernel - Re: [PATCH 2/3] pci: Generalize is

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Date:   Wed, 9 Aug 2017 11:02:41 -0600
From:   Jon Derrick <jonathan.derrick@...el.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     linux-pci@...r.kernel.org, iommu@...ts.linux-foundation.org,
        David Woodhouse <dwmw2@...radead.org>,
        Keith Busch <keith.busch@...el.com>,
        Scott Bauer <scott.bauer@...el.com>,
        David Fugate <david.fugate@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] pci: Generalize is_vmd behavior

On 08/11/2017 11:03 AM, Bjorn Helgaas wrote:
> On Mon, Aug 07, 2017 at 01:57:12PM -0600, Jon Derrick wrote:
>> Generalize is_vmd behavior to remove dependency on domain number
>> checking in pci quirks.
>>
>> Signed-off-by: Jon Derrick <jonathan.derrick@...el.com>
>> ---
>>  arch/x86/include/asm/pci.h | 8 +++-----
>>  arch/x86/pci/common.c      | 2 +-
>>  drivers/pci/quirks.c       | 2 +-
>>  include/linux/pci.h        | 4 ++++
>>  4 files changed, 9 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/pci.h b/arch/x86/include/asm/pci.h
>> index 473a729..5c5d54a 100644
>> --- a/arch/x86/include/asm/pci.h
>> +++ b/arch/x86/include/asm/pci.h
>> @@ -60,16 +60,14 @@ static inline void *_pci_root_bus_fwnode(struct pci_bus *bus)
>>  #define pci_root_bus_fwnode	_pci_root_bus_fwnode
>>  #endif
>>  
>> -static inline bool is_vmd(struct pci_bus *bus)
>> -{
>>  #if IS_ENABLED(CONFIG_VMD)
>> +static inline bool pci_bus_is_vmd(struct pci_bus *bus)
>> +{
>>  	struct pci_sysdata *sd = bus->sysdata;
>>  
>>  	return sd->vmd_domain;
>> -#else
>> -	return false;
>> -#endif
>>  }
>> +#endif
>>  
>>  /* Can be used to override the logic in pci_scan_bus for skipping
>>     already-configured bus numbers - to be used for buggy BIOSes
>> diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
>> index dbe2132..18b2277 100644
>> --- a/arch/x86/pci/common.c
>> +++ b/arch/x86/pci/common.c
>> @@ -662,7 +662,7 @@ static void set_dma_domain_ops(struct pci_dev *pdev) {}
>>  
>>  static void set_dev_domain_options(struct pci_dev *pdev)
>>  {
>> -	if (is_vmd(pdev->bus))
>> +	if (pci_bus_is_vmd(pdev->bus))
>>  		pdev->hotplug_user_indicators = 1;
>>  }
>>  
>> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
>> index 6967c6b..ba47995 100644
>> --- a/drivers/pci/quirks.c
>> +++ b/drivers/pci/quirks.c
>> @@ -4666,7 +4666,7 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x443, quirk_intel_qat_vf_cap);
>>  static void quirk_no_aersid(struct pci_dev *pdev)
>>  {
>>  	/* VMD Domain */
>> -	if (pdev->bus->sysdata && pci_domain_nr(pdev->bus) >= 0x10000)
>> +	if (pci_bus_is_vmd(pdev->bus))
> 
> I like this part ...
> 
>>  		pdev->bus->bus_flags |= PCI_BUS_FLAGS_NO_AERSID;
>>  }
>>  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x2030, quirk_no_aersid);
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index 4869e66..0299d8b 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -1471,6 +1471,10 @@ static inline int pci_proc_domain(struct pci_bus *bus) { return 0; }
>>  static inline int pci_get_new_domain_nr(void) { return -ENOSYS; }
>>  #endif /* CONFIG_PCI_DOMAINS */
>>  
>> +#if !IS_ENABLED(CONFIG_VMD)
>> +static inline bool pci_bus_is_vmd(struct pci_bus *bus) { return false; }
>> +#endif
> 
> But not so much this part.  VMD is (AFAIK) still fundamentally an
> x86-only thing, so I'd like it better if this could all be within
> arch/x86.  Could this be done by moving quirk_no_aersid() to
> arch/x86/pci/fixup.c?
> 
Thanks for pointing this out. I'll think of something different and
localize it to the x86 code domain.

> BTW, CONFIG_VMD in drivers/pci/host/Kconfig is currently "depends on
> SRCU".  I'm not a Kconfig expert, but that doesn't seem like an
> intuitive connection.  And it's the only such dependency on SRCU in
> the tree -- most other places use "select SRCU", which makes more
> sense to me.
I agree - most places use select SRCU. I'll add that to v2.

> 
>>  /*
>>   * Generic implementation for PCI domain support. If your
>>   * architecture does not need custom management of PCI
>> -- 
>> 2.9.4
>>