Messages in this thread | | | Subject | Re: [PATCH v7 1/7] PCI/ATS: Fix pci_prg_resp_pasid_required() dependency issues | From | Kuppuswamy Sathyanarayanan <> | Date | Thu, 3 Oct 2019 14:11:28 -0700 |
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On 10/3/19 2:01 PM, Bjorn Helgaas wrote: > On Thu, Oct 03, 2019 at 01:37:26PM -0700, Kuppuswamy Sathyanarayanan wrote: >> On Thu, Oct 03, 2019 at 02:04:13PM -0500, Bjorn Helgaas wrote: >>> On Thu, Oct 03, 2019 at 10:20:24AM -0700, Kuppuswamy Sathyanarayanan wrote: >>>> Hi Bjorn, >>>> >>>> Thanks for looking into this patch set. >>>> >>>> On 9/5/19 12:18 PM, Bjorn Helgaas wrote: >>>>> On Wed, Aug 28, 2019 at 03:14:01PM -0700, sathyanarayanan.kuppuswamy@linux.intel.com wrote: >>>>>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> >>>>>> >>>>>> Since pci_prg_resp_pasid_required() function has dependency on both >>>>>> PASID and PRI, define it only if both CONFIG_PCI_PRI and >>>>>> CONFIG_PCI_PASID config options are enabled. >>>>>> >>>>>> Fixes: e5567f5f6762 ("PCI/ATS: Add pci_prg_resp_pasid_required() >>>>>> interface.") >>>>> [Don't split tags, including "Fixes:" across lines] >>>>> >>>>> This definitely doesn't fix e5567f5f6762. That commit added >>>>> pci_prg_resp_pasid_required(), but with no dependency on >>>>> CONFIG_PCI_PRI or CONFIG_PCI_PASID. >>>>> >>>>> This patch is only required when a subsequent patch is applied. It >>>>> should be squashed into the commit that requires it so it's obvious >>>>> why it's needed. >>>>> >>>>> I've been poking at this series, and I'll post a v8 soon with this and >>>>> other fixes. >>>> In your v8 submission you did not merge this patch. You did not use >>>> pri_cap or pasid_cap cached values. Instead you have re-read the >>>> value from register. Is this intentional? >>>> >>>> Since this function will be called for every VF device we might loose some >>>> performance benefit. >>> This particular patch doesn't do any caching. IIRC it fiddles with >>> ifdefs to solve a problem that would be introduced by a future patch. >>> I don't remember the exact details, but I think the series I merged >>> doesn't have that problem. If it does, let me know the details and we >>> can fix it. >> This patch by itself does not do any caching. But your caching patch >> missed modifying this function to use cached values. Please check the >> current implementation of this function. It still reads >> PCI_EXT_CAP_ID_PRI register instead of using cached value. Please let >> me know your comments. >> >> int pci_prg_resp_pasid_required(struct pci_dev *pdev) >> { >> u16 status; >> int pri; >> >> if (pdev->is_virtfn) >> pdev = pci_physfn(pdev); >> >> pri = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI); >> if (!pri) >> return 0; >> >> pci_read_config_word(pdev, pri + PCI_PRI_STATUS, &status); >> >> if (status & PCI_PRI_STATUS_PASID) >> return 1; >> >> return 0; >> } >> EXPORT_SYMBOL_GPL(pci_prg_resp_pasid_required); >> >> If caching is applied to this function then we need this #ifdef >> dependency correction patch. > IIRC this #ifdef patch wasn't connected to the actual *need* for the > #ifdef, so it was very difficult to review. I thought this function > would be infrequently used and it wasn't worth trying to sort out the > #ifdef muddle to do the caching. But it does seem sort of pointless > to chase the capability list again here, so maybe it *is* worth > optimizing. > > The PRG Response PASID Required bit is read-only, so I wonder if it > would be simpler if we just read PCI_PRI_STATUS once and save the bit > in the struct pci_dev? We could do that in pci_enable_pri(), or if we > might need the value before that's called, we could add a > pci_pri_init() and do it there.
Yes, caching PASID Required bit in pci_pri_init() function would provide performance benefits. But another thing to consider is, since this bit is same for both PF/VF, is it worth to add this bit it to struct pci_dev?or struct pci_sriov is the more appropriate place?
> >>> I did include the caching patches for both PRI and PASID capabilities, >>> but they're only performance optimizations so I moved them to the end >>> so the functional fixes would be smaller and earlier in the series. >>> >>>>>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> >>>>>> --- >>>>>> drivers/pci/ats.c | 10 ++++++---- >>>>>> include/linux/pci-ats.h | 12 +++++++++--- >>>>>> 2 files changed, 15 insertions(+), 7 deletions(-) >>>>>> >>>>>> diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c >>>>>> index e18499243f84..cdd936d10f68 100644 >>>>>> --- a/drivers/pci/ats.c >>>>>> +++ b/drivers/pci/ats.c >>>>>> @@ -395,6 +395,8 @@ int pci_pasid_features(struct pci_dev *pdev) >>>>>> } >>>>>> EXPORT_SYMBOL_GPL(pci_pasid_features); >>>>>> +#ifdef CONFIG_PCI_PRI >>>>>> + >>>>>> /** >>>>>> * pci_prg_resp_pasid_required - Return PRG Response PASID Required bit >>>>>> * status. >>>>>> @@ -402,10 +404,8 @@ EXPORT_SYMBOL_GPL(pci_pasid_features); >>>>>> * >>>>>> * Returns 1 if PASID is required in PRG Response Message, 0 otherwise. >>>>>> * >>>>>> - * Even though the PRG response PASID status is read from PRI Status >>>>>> - * Register, since this API will mainly be used by PASID users, this >>>>>> - * function is defined within #ifdef CONFIG_PCI_PASID instead of >>>>>> - * CONFIG_PCI_PRI. >>>>>> + * Since this API has dependency on both PRI and PASID, protect it >>>>>> + * with both CONFIG_PCI_PRI and CONFIG_PCI_PASID. >>>>>> */ >>>>>> int pci_prg_resp_pasid_required(struct pci_dev *pdev) >>>>>> { >>>>>> @@ -425,6 +425,8 @@ int pci_prg_resp_pasid_required(struct pci_dev *pdev) >>>>>> } >>>>>> EXPORT_SYMBOL_GPL(pci_prg_resp_pasid_required); >>>>>> +#endif >>>>>> + >>>>>> #define PASID_NUMBER_SHIFT 8 >>>>>> #define PASID_NUMBER_MASK (0x1f << PASID_NUMBER_SHIFT) >>>>>> /** >>>>>> diff --git a/include/linux/pci-ats.h b/include/linux/pci-ats.h >>>>>> index 1ebb88e7c184..1a0bdaee2f32 100644 >>>>>> --- a/include/linux/pci-ats.h >>>>>> +++ b/include/linux/pci-ats.h >>>>>> @@ -40,7 +40,6 @@ void pci_disable_pasid(struct pci_dev *pdev); >>>>>> void pci_restore_pasid_state(struct pci_dev *pdev); >>>>>> int pci_pasid_features(struct pci_dev *pdev); >>>>>> int pci_max_pasids(struct pci_dev *pdev); >>>>>> -int pci_prg_resp_pasid_required(struct pci_dev *pdev); >>>>>> #else /* CONFIG_PCI_PASID */ >>>>>> @@ -67,11 +66,18 @@ static inline int pci_max_pasids(struct pci_dev *pdev) >>>>>> return -EINVAL; >>>>>> } >>>>>> +#endif /* CONFIG_PCI_PASID */ >>>>>> + >>>>>> +#if defined(CONFIG_PCI_PRI) && defined(CONFIG_PCI_PASID) >>>>>> + >>>>>> +int pci_prg_resp_pasid_required(struct pci_dev *pdev); >>>>>> + >>>>>> +#else /* CONFIG_PCI_PASID && CONFIG_PCI_PRI */ >>>>>> + >>>>>> static inline int pci_prg_resp_pasid_required(struct pci_dev *pdev) >>>>>> { >>>>>> return 0; >>>>>> } >>>>>> -#endif /* CONFIG_PCI_PASID */ >>>>>> - >>>>>> +#endif >>>>>> #endif /* LINUX_PCI_ATS_H*/ >>>>>> -- >>>>>> 2.21.0 >>>>>> >>>> -- >>>> Sathyanarayanan Kuppuswamy >>>> Linux kernel developer >>>> >> -- >> Sathyanarayanan Kuppuswamy >> Linux kernel developer
-- Sathyanarayanan Kuppuswamy Linux kernel developer
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