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Date: Mon, 12 Aug 2019 14:35:32 -0700
From: sathyanarayanan kuppuswamy
<sathyanarayanan.kuppuswamy@...ux.intel.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
ashok.raj@...el.com, keith.busch@...el.com
Subject: Re: [PATCH v5 2/7] PCI/ATS: Initialize PRI in pci_ats_init()
Hi,
Thanks for the review.
On 8/12/19 1:04 PM, Bjorn Helgaas wrote:
> On Thu, Aug 01, 2019 at 05:05:59PM -0700, sathyanarayanan.kuppuswamy@...ux.intel.com wrote:
>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
>>
>> Currently, PRI Capability checks are repeated across all PRI API's.
>> Instead, cache the capability check result in pci_pri_init() and use it
>> in other PRI API's. Also, since PRI is a shared resource between PF/VF,
>> initialize default values for common PRI features in pci_pri_init().
> This patch does two things, and it would be better if they were split:
>
> 1) Cache the PRI capability offset
> 2) Separate the PF and VF paths
Ok. I will split it into two patches in next version.
>
>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
>> ---
>> drivers/pci/ats.c | 80 ++++++++++++++++++++++++++++-------------
>> include/linux/pci-ats.h | 5 +++
>> include/linux/pci.h | 1 +
>> 3 files changed, 61 insertions(+), 25 deletions(-)
>>
>> diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
>> index cdd936d10f68..280be911f190 100644
>> --- a/drivers/pci/ats.c
>> +++ b/drivers/pci/ats.c
>> @@ -28,6 +28,8 @@ void pci_ats_init(struct pci_dev *dev)
>> return;
>>
>> dev->ats_cap = pos;
>> +
>> + pci_pri_init(dev);
>> }
>>
>> /**
>> @@ -170,36 +172,72 @@ int pci_ats_page_aligned(struct pci_dev *pdev)
>> EXPORT_SYMBOL_GPL(pci_ats_page_aligned);
>>
>> #ifdef CONFIG_PCI_PRI
>> +
>> +void pci_pri_init(struct pci_dev *pdev)
>> +{
>> + u32 max_requests;
>> + int pos;
>> +
>> + /*
>> + * As per PCIe r4.0, sec 9.3.7.11, only PF is permitted to
>> + * implement PRI and all associated VFs can only use it.
>> + * Since PF already initialized the PRI parameters there is
>> + * no need to proceed further.
>> + */
>> + if (pdev->is_virtfn)
>> + return;
>> +
>> + pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
>> + if (!pos)
>> + return;
>> +
>> + pci_read_config_dword(pdev, pos + PCI_PRI_MAX_REQ, &max_requests);
>> +
>> + /*
>> + * Since PRI is a shared resource between PF and VF, we must not
>> + * configure Outstanding Page Allocation Quota as a per device
>> + * resource in pci_enable_pri(). So use maximum value possible
>> + * as default value.
>> + */
>> + pci_write_config_dword(pdev, pos + PCI_PRI_ALLOC_REQ, max_requests);
>> +
>> + pdev->pri_reqs_alloc = max_requests;
>> + pdev->pri_cap = pos;
>> +}
>> +
>> /**
>> * pci_enable_pri - Enable PRI capability
>> * @ pdev: PCI device structure
>> *
>> * Returns 0 on success, negative value on error
>> + *
>> + * TODO: Since PRI is a shared resource between PF/VF, don't update
>> + * Outstanding Page Allocation Quota in the same API as a per device
>> + * feature.
>> */
>> int pci_enable_pri(struct pci_dev *pdev, u32 reqs)
>> {
>> u16 control, status;
>> u32 max_requests;
>> - int pos;
>>
>> if (WARN_ON(pdev->pri_enabled))
>> return -EBUSY;
>>
>> - pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
>> - if (!pos)
>> + if (!pdev->pri_cap)
>> return -EINVAL;
>>
>> - pci_read_config_word(pdev, pos + PCI_PRI_STATUS, &status);
>> + pci_read_config_word(pdev, pdev->pri_cap + PCI_PRI_STATUS, &status);
>> if (!(status & PCI_PRI_STATUS_STOPPED))
>> return -EBUSY;
>>
>> - pci_read_config_dword(pdev, pos + PCI_PRI_MAX_REQ, &max_requests);
>> + pci_read_config_dword(pdev, pdev->pri_cap + PCI_PRI_MAX_REQ,
>> + &max_requests);
>> reqs = min(max_requests, reqs);
>> pdev->pri_reqs_alloc = reqs;
>> - pci_write_config_dword(pdev, pos + PCI_PRI_ALLOC_REQ, reqs);
>> + pci_write_config_dword(pdev, pdev->pri_cap + PCI_PRI_ALLOC_REQ, reqs);
> The comment above says "don't update Outstanding Page Allocation
> Quota" but it looks like that's what this is doing.
I don't want to fix it in the current patch-set. It needs further
scrutiny. That's why I have added the TODO comment for it.
Currently, intel-iommu and amd-iommu drivers (only users of
pci_enable_pri()) hard-codes 32 as a default value for Outstanding Page
Allocation Quota. Only exception is, amd-iommu sets this value as 1 for
devices with erratum AMD_PRI_DEV_ERRATUM_LIMIT_REQ_ONE. There is no
comment or spec reference that explains why 32 is chosen as default
value. Also configuring 32 as per device max value will break for PF/VF
devices since they share the PRI interface. So without clear history, I
don't want to make any changes which might affect their functionality.
IMO, the correct way is to configure the Outstanding Page Allocation
Quota with maximum value in pci_pri_init(). So, even if IOMMU can't
handle more than 32 page request per device, it can fail properly and it
should not affect the functionality.
I have added proper configuration for Outstanding Page Allocation Quota
in pci_pri_init(), but it does not serve any purpose until we fix the
part of the issue in pci_enable_pri(). If you want, I can remove it for
now, and add it when fixing the issue in pci_enable_pri().
>
>> control = PCI_PRI_CTRL_ENABLE;
>> - pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);
>> + pci_write_config_word(pdev, pdev->pri_cap + PCI_PRI_CTRL, control);
>>
>> pdev->pri_enabled = 1;
>>
>> @@ -216,18 +254,16 @@ EXPORT_SYMBOL_GPL(pci_enable_pri);
>> void pci_disable_pri(struct pci_dev *pdev)
>> {
>> u16 control;
>> - int pos;
>>
>> if (WARN_ON(!pdev->pri_enabled))
>> return;
>>
>> - pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
>> - if (!pos)
>> + if (!pdev->pri_cap)
>> return;
>>
>> - pci_read_config_word(pdev, pos + PCI_PRI_CTRL, &control);
>> + pci_read_config_word(pdev, pdev->pri_cap + PCI_PRI_CTRL, &control);
>> control &= ~PCI_PRI_CTRL_ENABLE;
>> - pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);
>> + pci_write_config_word(pdev, pdev->pri_cap + PCI_PRI_CTRL, control);
>>
>> pdev->pri_enabled = 0;
>> }
>> @@ -241,17 +277,15 @@ void pci_restore_pri_state(struct pci_dev *pdev)
>> {
>> u16 control = PCI_PRI_CTRL_ENABLE;
>> u32 reqs = pdev->pri_reqs_alloc;
>> - int pos;
>>
>> if (!pdev->pri_enabled)
>> return;
>>
>> - pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
>> - if (!pos)
>> + if (!pdev->pri_cap)
>> return;
>>
>> - pci_write_config_dword(pdev, pos + PCI_PRI_ALLOC_REQ, reqs);
>> - pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);
>> + pci_write_config_dword(pdev, pdev->pri_cap + PCI_PRI_ALLOC_REQ, reqs);
>> + pci_write_config_word(pdev, pdev->pri_cap + PCI_PRI_CTRL, control);
>> }
>> EXPORT_SYMBOL_GPL(pci_restore_pri_state);
>>
>> @@ -265,17 +299,15 @@ EXPORT_SYMBOL_GPL(pci_restore_pri_state);
>> int pci_reset_pri(struct pci_dev *pdev)
>> {
>> u16 control;
>> - int pos;
>>
>> if (WARN_ON(pdev->pri_enabled))
>> return -EBUSY;
>>
>> - pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
>> - if (!pos)
>> + if (!pdev->pri_cap)
>> return -EINVAL;
>>
>> control = PCI_PRI_CTRL_RESET;
>> - pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);
>> + pci_write_config_word(pdev, pdev->pri_cap + PCI_PRI_CTRL, control);
>>
>> return 0;
>> }
>> @@ -410,13 +442,11 @@ EXPORT_SYMBOL_GPL(pci_pasid_features);
>> int pci_prg_resp_pasid_required(struct pci_dev *pdev)
>> {
>> u16 status;
>> - int pos;
>>
>> - pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
>> - if (!pos)
>> + if (!pdev->pri_cap)
>> return 0;
>>
>> - pci_read_config_word(pdev, pos + PCI_PRI_STATUS, &status);
>> + pci_read_config_word(pdev, pdev->pri_cap + PCI_PRI_STATUS, &status);
>>
>> if (status & PCI_PRI_STATUS_PASID)
>> return 1;
>> diff --git a/include/linux/pci-ats.h b/include/linux/pci-ats.h
>> index 1a0bdaee2f32..33653d4ca94f 100644
>> --- a/include/linux/pci-ats.h
>> +++ b/include/linux/pci-ats.h
>> @@ -6,6 +6,7 @@
>>
>> #ifdef CONFIG_PCI_PRI
>>
>> +void pci_pri_init(struct pci_dev *pdev);
> I think this could be moved to drivers/pci/pci.h, since it doesn't
> need to be visible outside drivers/pci/.
Makes sense. I will move it.
>
>> int pci_enable_pri(struct pci_dev *pdev, u32 reqs);
>> void pci_disable_pri(struct pci_dev *pdev);
>> void pci_restore_pri_state(struct pci_dev *pdev);
>> @@ -13,6 +14,10 @@ int pci_reset_pri(struct pci_dev *pdev);
>>
>> #else /* CONFIG_PCI_PRI */
>>
>> +static inline void pci_pri_init(struct pci_dev *pdev)
>> +{
>> +}
>> +
>> static inline int pci_enable_pri(struct pci_dev *pdev, u32 reqs)
>> {
>> return -ENODEV;
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index 9e700d9f9f28..56b55db099fc 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -455,6 +455,7 @@ struct pci_dev {
>> atomic_t ats_ref_cnt; /* Number of VFs with ATS enabled */
>> #endif
>> #ifdef CONFIG_PCI_PRI
>> + u16 pri_cap; /* PRI Capability offset */
>> u32 pri_reqs_alloc; /* Number of PRI requests allocated */
>> #endif
>> #ifdef CONFIG_PCI_PASID
>> --
>> 2.21.0
>>
--
Sathyanarayanan Kuppuswamy
Linux kernel developer
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