Re: [PATCH v6 2/6] PCI: Add a helper to convert between VF BAR number and IOV resource

[Ilpo Järvinen]

On Thu, 20 Mar 2025, Michał Winiarski wrote:

> There are multiple places where conversions between IOV resources and
> corresponding VF BAR numbers are done.
> 
> Extract the logic to pci_resource_num_from_vf_bar() and
> pci_resource_num_to_vf_bar() helpers.
> 
> Suggested-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> Signed-off-by: Michał Winiarski <michal.winiarski@xxxxxxxxx>
> Acked-by: Christian König <christian.koenig@xxxxxxx>
> ---
>  drivers/pci/iov.c       | 22 ++++++++++++----------
>  drivers/pci/pci.h       | 19 +++++++++++++++++++
>  drivers/pci/setup-bus.c |  3 ++-
>  3 files changed, 33 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index bf95387993cd5..985ea11339c45 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -151,7 +151,7 @@ resource_size_t pci_iov_resource_size(struct pci_dev *dev, int resno)
>  	if (!dev->is_physfn)
>  		return 0;
>  
> -	return dev->sriov->barsz[resno - PCI_IOV_RESOURCES];
> +	return dev->sriov->barsz[pci_resource_num_to_vf_bar(resno)];
>  }
>  
>  static void pci_read_vf_config_common(struct pci_dev *virtfn)
> @@ -322,12 +322,13 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
>  	virtfn->multifunction = 0;
>  
>  	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
> -		res = &dev->resource[i + PCI_IOV_RESOURCES];
> +		res = &dev->resource[pci_resource_num_from_vf_bar(i)];
>  		if (!res->parent)
>  			continue;
>  		virtfn->resource[i].name = pci_name(virtfn);
>  		virtfn->resource[i].flags = res->flags;
> -		size = pci_iov_resource_size(dev, i + PCI_IOV_RESOURCES);
> +		size = pci_iov_resource_size(dev,
> +					     pci_resource_num_from_vf_bar(i));
>  		resource_set_range(&virtfn->resource[i],
>  				   res->start + size * id, size);
>  		rc = request_resource(res, &virtfn->resource[i]);
> @@ -624,8 +625,8 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn)
>  
>  	nres = 0;
>  	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
> -		bars |= (1 << (i + PCI_IOV_RESOURCES));
> -		res = &dev->resource[i + PCI_IOV_RESOURCES];
> +		bars |= (1 << pci_resource_num_from_vf_bar(i));
> +		res = &dev->resource[pci_resource_num_from_vf_bar(i)];
>  		if (res->parent)
>  			nres++;
>  	}
> @@ -791,8 +792,9 @@ static int sriov_init(struct pci_dev *dev, int pos)
>  
>  	nres = 0;
>  	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
> -		res = &dev->resource[i + PCI_IOV_RESOURCES];
> -		res_name = pci_resource_name(dev, i + PCI_IOV_RESOURCES);
> +		res = &dev->resource[pci_resource_num_from_vf_bar(i)];
> +		res_name = pci_resource_name(dev,
> +					     pci_resource_num_from_vf_bar(i));

All these get easier to read if you add (same comment for the cases 
above):

		int idx = pci_resource_num_from_vf_bar(i);

>  
>  		/*
>  		 * If it is already FIXED, don't change it, something
> @@ -851,7 +853,7 @@ static int sriov_init(struct pci_dev *dev, int pos)
>  	dev->is_physfn = 0;
>  failed:
>  	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
> -		res = &dev->resource[i + PCI_IOV_RESOURCES];
> +		res = &dev->resource[pci_resource_num_from_vf_bar(i)];
>  		res->flags = 0;
>  	}
>  
> @@ -913,7 +915,7 @@ static void sriov_restore_state(struct pci_dev *dev)
>  	pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL, ctrl);
>  
>  	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++)
> -		pci_update_resource(dev, i + PCI_IOV_RESOURCES);
> +		pci_update_resource(dev, pci_resource_num_from_vf_bar(i));
>  
>  	pci_write_config_dword(dev, iov->pos + PCI_SRIOV_SYS_PGSIZE, iov->pgsz);
>  	pci_iov_set_numvfs(dev, iov->num_VFs);
> @@ -979,7 +981,7 @@ void pci_iov_update_resource(struct pci_dev *dev, int resno)
>  {
>  	struct pci_sriov *iov = dev->is_physfn ? dev->sriov : NULL;
>  	struct resource *res = pci_resource_n(dev, resno);
> -	int vf_bar = resno - PCI_IOV_RESOURCES;
> +	int vf_bar = pci_resource_num_to_vf_bar(resno);
>  	struct pci_bus_region region;
>  	u16 cmd;
>  	u32 new;
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index adc54bb2c8b34..f44840ee3c327 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -693,6 +693,15 @@ static inline bool pci_resource_is_iov(int resno)
>  {
>  	return resno >= PCI_IOV_RESOURCES && resno <= PCI_IOV_RESOURCE_END;
>  }
> +static inline int pci_resource_num_from_vf_bar(int resno)
> +{
> +	return resno + PCI_IOV_RESOURCES;
> +}
> +
> +static inline int pci_resource_num_to_vf_bar(int resno)
> +{
> +	return resno - PCI_IOV_RESOURCES;
> +}
>  extern const struct attribute_group sriov_pf_dev_attr_group;
>  extern const struct attribute_group sriov_vf_dev_attr_group;
>  #else
> @@ -717,6 +726,16 @@ static inline bool pci_resource_is_iov(int resno)
>  {
>  	return false;
>  }
> +static inline int pci_resource_num_from_vf_bar(int resno)
> +{
> +	WARN_ON_ONCE(1);
> +	return -ENODEV;
> +}
> +static inline int pci_resource_num_to_vf_bar(int resno)
> +{
> +	WARN_ON_ONCE(1);
> +	return -ENODEV;
> +}
>  #endif /* CONFIG_PCI_IOV */
>  
>  #ifdef CONFIG_PCIE_TPH
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index 54d6f4fa3ce16..55e91ba1e74a2 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -1885,7 +1885,8 @@ static int iov_resources_unassigned(struct pci_dev *dev, void *data)
>  	bool *unassigned = data;
>  
>  	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
> -		struct resource *r = &dev->resource[i + PCI_IOV_RESOURCES];
> +		struct resource *r =
> +			&dev->resource[pci_resource_num_from_vf_bar(i)];

I'd add int idx here as well.

>  		struct pci_bus_region region;
>  
>  		/* Not assigned or rejected by kernel? */
> 

-- 
 i.