linux-kernel - Re: [PATCH v2 1/2] PCI/ATS: Add pci_prg_resp_pasid

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Date:   Wed, 13 Feb 2019 13:49:57 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     sathyanarayanan.kuppuswamy@...ux.intel.com
Cc:     joro@...tes.org, dwmw2@...radead.org, linux-pci@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        ashok.raj@...el.com, jacob.jun.pan@...el.com,
        keith.busch@...el.com, Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: Re: [PATCH v2 1/2] PCI/ATS: Add pci_prg_resp_pasid_required()
 interface.

On Mon, Feb 11, 2019 at 01:50:31PM -0800, sathyanarayanan.kuppuswamy@...ux.intel.com wrote:
> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> 
> Return the PRG Response PASID Required bit in the Page Request
> Status Register.
> 
> As per PCIe spec r4.0, sec 10.5.2.3, if this bit is Set then the device
> expects a PASID TLP Prefix on PRG Response Messages when the
> corresponding Page Requests had a PASID TLP Prefix. If Clear, the device
> does not expect PASID TLP Prefixes on any PRG Response Message, and the
> device behavior is undefined if this bit is Clear and the device
> receives a PRG Response Message with a PASID TLP Prefix. Also the device
> behavior is undefined in the this bit is Set and the device receives a
> PRG Response Message with no PASID TLP Prefix when the corresponding
> Page Requests had a PASID TLP Prefix.

s/Set then the device/Set, the device/
s/undefined if this bit is Clear and the device/undefined if the device/
s/is undefined in the this/is undefined if this/

> This function will be used by drivers like IOMMU, if it is required to
> check the status of the PRG Response PASID Required bit before enabling
> the PASID support of the device.
> 
> Cc: Ashok Raj <ashok.raj@...el.com>
> Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> Cc: Keith Busch <keith.busch@...el.com>
> Suggested-by: Ashok Raj <ashok.raj@...el.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>

With typos (also below) addressed,

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

> ---
>  drivers/pci/ats.c             | 31 +++++++++++++++++++++++++++++++
>  include/linux/pci-ats.h       |  5 +++++
>  include/uapi/linux/pci_regs.h |  1 +
>  3 files changed, 37 insertions(+)
> 
> diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
> index 5b78f3b1b918..f843cd846dff 100644
> --- a/drivers/pci/ats.c
> +++ b/drivers/pci/ats.c
> @@ -368,6 +368,37 @@ int pci_pasid_features(struct pci_dev *pdev)
>  }
>  EXPORT_SYMBOL_GPL(pci_pasid_features);
>  
> +/**
> + * pci_prg_resp_pasid_required - Return PRG Response PASID Required bit
> + *				 status.
> + * @pdev: PCI device structure
> + *
> + * 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.
> + *

Remove blank comment line.

> + */
> +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)
> +		return 0;
> +
> +	pci_read_config_word(pdev, pos + PCI_PRI_STATUS, &status);
> +
> +	if (status & PCI_PRI_STATUS_PASID)
> +		return 1;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(pci_prg_resp_pasid_required);
> +
>  #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 7c4b8e27268c..facfd6a18fe1 100644
> --- a/include/linux/pci-ats.h
> +++ b/include/linux/pci-ats.h
> @@ -40,6 +40,7 @@ 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 */
>  
> @@ -66,6 +67,10 @@ static inline int pci_max_pasids(struct pci_dev *pdev)
>  	return -EINVAL;
>  }
>  
> +static int pci_prg_resp_pasid_required(struct pci_dev *pdev)
> +{
> +	return 0;
> +}
>  #endif /* CONFIG_PCI_PASID */
>  
>  
> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index e1e9888c85e6..898be572b010 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -880,6 +880,7 @@
>  #define  PCI_PRI_STATUS_RF	0x001	/* Response Failure */
>  #define  PCI_PRI_STATUS_UPRGI	0x002	/* Unexpected PRG index */
>  #define  PCI_PRI_STATUS_STOPPED	0x100	/* PRI Stopped */
> +#define  PCI_PRI_STATUS_PASID	0x8000	/* PRG Response PASID Required */
>  #define PCI_PRI_MAX_REQ		0x08	/* PRI max reqs supported */
>  #define PCI_PRI_ALLOC_REQ	0x0c	/* PRI max reqs allowed */
>  #define PCI_EXT_CAP_PRI_SIZEOF	16
> -- 
> 2.20.1
>