Re: [PATCH v2] PCI:vmd: add the module param to adjust msi mode

[Bjorn Helgaas <helgaas@kernel.org>]

Please adjust the subject line to match previous history, e.g.,

  PCI: vmd: Add ... MSI ...

On Tue, Mar 07, 2023 at 04:35:59PM +0800, korantwork@gmail.com wrote:
> From: Xinghui Li <korantli@tencent.com>
> 
> In the legacy, the vmd msi-mode can only be adjusted by configing
> 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 affect the existing settings of the device.

Please add a space after the period that ends each sentence.
Capitalize "MSI" to match usage in spec.

> Signed-off-by: Xinghui Li <korantli@tencent.com>
> Reviewed-by: Nirmal Patel <nirmal.patel@linux.intel.com>

I didn't see a response from Nirmal on the mailing list with the
Reviewed-by.  I think it's better if Nirmal responds to the patch
directly on the mailing list with the Reviewed-by, and whoever applies
the patch can incorporate it.  Otherwise we have no visibility into
any interaction between you and Nirmal.

> ---
>  drivers/pci/controller/vmd.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> index 990630ec57c6..8b42b2c1d949 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -34,6 +34,20 @@
>  #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:
> + *
> + * 1-off
> + * 2-on

It looks like your code matches either "on" or "off", not "1" or "2".

> + * The default param is "NULL", the goal is not to affect the existing
> + * settings of the device.
> + */
> +char *msi_remap = "NULL";

Looks like this should be static?  And using "NULL" (as opposed to
something like the empty string "") suggests some intrinsic meaning of
"NULL", but I think there is no intrinsic meaning and the only point
is that "NULL" doesn't match either "on" or "off".

> +module_param(msi_remap, charp, 0444);
> +
>  enum vmd_features {
>  	/*
>  	 * Device may contain registers which hint the physical location of the
> @@ -875,6 +889,7 @@ 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-x\n");
>  
>  		ret = vmd_create_irq_domain(vmd);
>  		if (ret)
> @@ -887,6 +902,7 @@ 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-x\n");
>  	}
>  
>  	pci_add_resource(&resources, &vmd->resources[0]);
> @@ -955,6 +971,14 @@ 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 (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 +1008,8 @@ 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;
> -- 
> 2.31.1
>