linux-kernel - Re: [PATCH v3] PCI: vmd: Add the module param to adjust MSI mode

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Message-ID: <44b1519b-f9e0-476a-ff47-8d21f004b3cd@linux.intel.com>
Date:   Fri, 17 Mar 2023 14:31:49 -0700
From:   "Patel, Nirmal" <nirmal.patel@...ux.intel.com>
To:     korantwork@...il.com, helgaas@...nel.org, kbusch@...nel.org,
        jonathan.derrick@...ux.dev, lpieralisi@...nel.org
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xinghui Li <korantli@...cent.com>
Subject: Re: [PATCH v3] PCI: vmd: Add the module param to adjust MSI mode

On 3/16/2023 5:23 AM, korantwork@...il.com wrote:
> From: Xinghui Li <korantli@...cent.com>
>
> In the legacy, the vmd MSI mode can only be adjusted by configing

configuring

> vmd_ids table. This patch adds another way to adjust MSI mode by
> adjusting module param, which allow users easier to adjust the vmd
> according to the I/O scenario without rebuilding driver. There are two
> params could be recognized: on, off. The default param is NULL,
> the goal is not to effect the existing settings of the device.
>
> Signed-off-by: Xinghui Li <korantli@...cent.com>
> ---
>  drivers/pci/controller/vmd.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
>
> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> index 990630ec57c6..fb61181baa9e 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -34,6 +34,19 @@
>  #define MB2_SHADOW_OFFSET	0x2000
>  #define MB2_SHADOW_SIZE		16
>  
> +/*
> + * The VMD msi_remap module parameter provides the alternative way
> + * to adjust MSI mode when loading vmd.ko other than vmd_ids table.
> + * There are two params could be recognized:
> + *
> + * off: enable MSI bypass

What about this?
off: disable MSI remapping

> + * on: enable MSI remapping
> + *
> + */
> +static char *msi_remap;
> +module_param(msi_remap, charp, 0444);
> +MODULE_PARM_DESC(msi_remap, "Whether to enable MSI remapping function");
> +
>  enum vmd_features {
>  	/*
>  	 * Device may contain registers which hint the physical location of the
> @@ -875,6 +888,7 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
>  			return ret;
>  
>  		vmd_set_msi_remapping(vmd, true);
> +		dev_info(&vmd->dev->dev, "init vmd with remapping MSI\n");
>  
>  		ret = vmd_create_irq_domain(vmd);
>  		if (ret)
> @@ -887,6 +901,7 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
>  		irq_domain_update_bus_token(vmd->irq_domain, DOMAIN_BUS_VMD_MSI);
>  	} else {
>  		vmd_set_msi_remapping(vmd, false);
> +		dev_info(&vmd->dev->dev, "init vmd with bypass MSI\n");
>  	}
>  
>  	pci_add_resource(&resources, &vmd->resources[0]);
> @@ -955,6 +970,16 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
>  	return 0;
>  }
>  
> +static void vmd_config_msi_remap_param(unsigned long *features)
> +{
> +	if (msi_remap) {
> +		if (strcmp(msi_remap, "on") == 0)
> +			*features &= ~(VMD_FEAT_CAN_BYPASS_MSI_REMAP);
> +		else if (strcmp(msi_remap, "off") == 0)
> +			*features |= VMD_FEAT_CAN_BYPASS_MSI_REMAP;
> +	}
> +}
> +
>  static int vmd_probe(struct pci_dev *dev, const struct pci_device_id *id)
>  {
>  	unsigned long features = (unsigned long) id->driver_data;
> @@ -984,6 +1009,8 @@ static int vmd_probe(struct pci_dev *dev, const struct pci_device_id *id)
>  	if (err < 0)
>  		goto out_release_instance;
>  
> +	vmd_config_msi_remap_param(&features);
> +
>  	vmd->cfgbar = pcim_iomap(dev, VMD_CFGBAR, 0);
>  	if (!vmd->cfgbar) {
>  		err = -ENOMEM;

Reviewed-by: Nirmal Patel <nirmal.patel@...ux.intel.com>

Thanks