linux-kernel - Re: [PATCH v3 03/12] fpga: dfl: pci: enable SRIOV support.

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Date:   Wed, 24 Jul 2019 11:37:44 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Wu Hao <hao.wu@...el.com>
Cc:     mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        linux-doc@...r.kernel.org, atull@...nel.org,
        Zhang Yi Z <yi.z.zhang@...el.com>,
        Xu Yilun <yilun.xu@...el.com>
Subject: Re: [PATCH v3 03/12] fpga: dfl: pci: enable SRIOV support.

On Tue, Jul 23, 2019 at 12:51:26PM +0800, Wu Hao wrote:
> This patch enables the standard sriov support. It allows user to
> enable SRIOV (and VFs), then user could pass through accelerators
> (VFs) into virtual machine or use VFs directly in host.
> 
> Signed-off-by: Zhang Yi Z <yi.z.zhang@...el.com>
> Signed-off-by: Xu Yilun <yilun.xu@...el.com>
> Signed-off-by: Wu Hao <hao.wu@...el.com>
> Acked-by: Alan Tull <atull@...nel.org>
> Acked-by: Moritz Fischer <mdf@...nel.org>
> Signed-off-by: Moritz Fischer <mdf@...nel.org>
> ---
> v2: remove DRV/MODULE_VERSION modifications.
> ---
>  drivers/fpga/dfl-pci.c | 39 +++++++++++++++++++++++++++++++++++++++
>  drivers/fpga/dfl.c     | 41 +++++++++++++++++++++++++++++++++++++++++
>  drivers/fpga/dfl.h     |  1 +
>  3 files changed, 81 insertions(+)
> 
> diff --git a/drivers/fpga/dfl-pci.c b/drivers/fpga/dfl-pci.c
> index 66b5720..0e65d81 100644
> --- a/drivers/fpga/dfl-pci.c
> +++ b/drivers/fpga/dfl-pci.c
> @@ -223,8 +223,46 @@ int cci_pci_probe(struct pci_dev *pcidev, const struct pci_device_id *pcidevid)
>  	return ret;
>  }
>  
> +static int cci_pci_sriov_configure(struct pci_dev *pcidev, int num_vfs)
> +{
> +	struct cci_drvdata *drvdata = pci_get_drvdata(pcidev);
> +	struct dfl_fpga_cdev *cdev = drvdata->cdev;
> +	int ret = 0;
> +
> +	mutex_lock(&cdev->lock);
> +
> +	if (!num_vfs) {
> +		/*
> +		 * disable SRIOV and then put released ports back to default
> +		 * PF access mode.
> +		 */
> +		pci_disable_sriov(pcidev);
> +
> +		__dfl_fpga_cdev_config_port_vf(cdev, false);
> +
> +	} else if (cdev->released_port_num == num_vfs) {
> +		/*
> +		 * only enable SRIOV if cdev has matched released ports, put
> +		 * released ports into VF access mode firstly.
> +		 */
> +		__dfl_fpga_cdev_config_port_vf(cdev, true);
> +
> +		ret = pci_enable_sriov(pcidev, num_vfs);
> +		if (ret)
> +			__dfl_fpga_cdev_config_port_vf(cdev, false);
> +	} else {
> +		ret = -EINVAL;
> +	}
> +
> +	mutex_unlock(&cdev->lock);
> +	return ret;
> +}
> +
>  static void cci_pci_remove(struct pci_dev *pcidev)
>  {
> +	if (dev_is_pf(&pcidev->dev))
> +		cci_pci_sriov_configure(pcidev, 0);
> +
>  	cci_remove_feature_devs(pcidev);
>  	pci_disable_pcie_error_reporting(pcidev);
>  }
> @@ -234,6 +272,7 @@ static void cci_pci_remove(struct pci_dev *pcidev)
>  	.id_table = cci_pcie_id_tbl,
>  	.probe = cci_pci_probe,
>  	.remove = cci_pci_remove,
> +	.sriov_configure = cci_pci_sriov_configure,
>  };
>  
>  module_pci_driver(cci_pci_driver);
> diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
> index e04ed45..c3a8e1d 100644
> --- a/drivers/fpga/dfl.c
> +++ b/drivers/fpga/dfl.c
> @@ -1112,6 +1112,47 @@ int dfl_fpga_cdev_config_port(struct dfl_fpga_cdev *cdev, int port_id,
>  }
>  EXPORT_SYMBOL_GPL(dfl_fpga_cdev_config_port);
>  
> +static void config_port_vf(struct device *fme_dev, int port_id, bool is_vf)
> +{
> +	void __iomem *base;
> +	u64 v;
> +
> +	base = dfl_get_feature_ioaddr_by_id(fme_dev, FME_FEATURE_ID_HEADER);
> +
> +	v = readq(base + FME_HDR_PORT_OFST(port_id));
> +
> +	v &= ~FME_PORT_OFST_ACC_CTRL;
> +	v |= FIELD_PREP(FME_PORT_OFST_ACC_CTRL,
> +			is_vf ? FME_PORT_OFST_ACC_VF : FME_PORT_OFST_ACC_PF);
> +
> +	writeq(v, base + FME_HDR_PORT_OFST(port_id));
> +}
> +
> +/**
> + * __dfl_fpga_cdev_config_port_vf - configure port to VF access mode
> + *
> + * @cdev: parent container device.
> + * @if_vf: true for VF access mode, and false for PF access mode
> + *
> + * Return: 0 on success, negative error code otherwise.
> + *
> + * This function is needed in sriov configuration routine. It could be used to
> + * configures the released ports access mode to VF or PF.
> + * The caller needs to hold lock for protection.
> + */
> +void __dfl_fpga_cdev_config_port_vf(struct dfl_fpga_cdev *cdev, bool is_vf)
> +{
> +	struct dfl_feature_platform_data *pdata;
> +
> +	list_for_each_entry(pdata, &cdev->port_dev_list, node) {
> +		if (device_is_registered(&pdata->dev->dev))
> +			continue;
> +
> +		config_port_vf(cdev->fme_dev, pdata->id, is_vf);
> +	}
> +}
> +EXPORT_SYMBOL_GPL(__dfl_fpga_cdev_config_port_vf);

Why are you exporting a function with a leading __?

You are expecting someone else, in who knows what code, to do locking
correctly?  If so, and the caller always has to have a local lock, then
it's not a big deal, just drop the '__', otherwise if you have to have a
specific lock for a specific device, then you have a really complex and
probably broken api here :(

thanks,

greg k-h