Re: [PATCH v5 3/6] PCI: Allow IOV resources to be resized in pci_resize_resource()

[Ilpo Järvinen]

On Wed, 12 Mar 2025, Michał Winiarski wrote:

> Similar to regular resizable BAR, VF BAR can also be resized.
> 
> The structures are very similar, which means we can reuse most of the
> implementation.
> 
> Extend the pci_resize_resource() function to accept IOV resources.
> 
> See PCIe r4.0, sec 9.3.7.4.
> 
> Signed-off-by: Michał Winiarski <michal.winiarski@xxxxxxxxx>
> ---
>  drivers/pci/iov.c       | 21 +++++++++++++++++++++
>  drivers/pci/pci.c       | 10 +++++++++-
>  drivers/pci/pci.h       |  9 +++++++++
>  drivers/pci/setup-res.c | 35 ++++++++++++++++++++++++++++++-----
>  4 files changed, 69 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 23c741e9ede89..7cc17e898cea7 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -154,6 +154,27 @@ resource_size_t pci_iov_resource_size(struct pci_dev *dev, int resno)
>  	return dev->sriov->barsz[pci_resource_num_to_vf_bar(resno)];
>  }
>  
> +void pci_iov_resource_set_size(struct pci_dev *dev, int resno,
> +			       resource_size_t size)
> +{
> +	if (!pci_resource_is_iov(resno)) {
> +		pci_warn(dev, "%s is not an IOV resource\n",
> +			 pci_resource_name(dev, resno));
> +		return;
> +	}
> +
> +	dev->sriov->barsz[pci_resource_num_to_vf_bar(resno)] = size;
> +}
> +
> +bool pci_iov_is_memory_decoding_enabled(struct pci_dev *dev)
> +{
> +	u16 cmd;
> +
> +	pci_read_config_word(dev, dev->sriov->pos + PCI_SRIOV_CTRL, &cmd);
> +
> +	return cmd & PCI_SRIOV_CTRL_MSE;
> +}
> +
>  static void pci_read_vf_config_common(struct pci_dev *virtfn)
>  {
>  	struct pci_dev *physfn = virtfn->physfn;
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 72ac91e359aaf..e6a986ad24d61 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -3731,8 +3731,16 @@ static int pci_rebar_find_pos(struct pci_dev *pdev, int bar)
>  {
>  	unsigned int pos, nbars, i;
>  	u32 ctrl;
> +	int cap;
>  
> -	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_REBAR);
> +	if (pci_resource_is_iov(bar)) {
> +		cap = PCI_EXT_CAP_ID_VF_REBAR;
> +		bar = pci_resource_num_to_vf_bar(bar);
> +	} else {
> +		cap = PCI_EXT_CAP_ID_REBAR;
> +	}

Use the cached values here.

> +
> +	pos = pci_find_ext_capability(pdev, cap);
>  	if (!pos)
>  		return -ENOTSUPP;
>  
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index e3cd9b8f9b734..af41f6c24451f 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -655,6 +655,9 @@ void pci_iov_update_resource(struct pci_dev *dev, int resno);
>  resource_size_t pci_sriov_resource_alignment(struct pci_dev *dev, int resno);
>  void pci_restore_iov_state(struct pci_dev *dev);
>  int pci_iov_bus_range(struct pci_bus *bus);
> +void pci_iov_resource_set_size(struct pci_dev *dev, int resno,
> +			       resource_size_t size);
> +bool pci_iov_is_memory_decoding_enabled(struct pci_dev *dev);
>  static inline bool pci_resource_is_iov(int resno)
>  {
>  	return resno >= PCI_IOV_RESOURCES && resno <= PCI_IOV_RESOURCE_END;
> @@ -688,6 +691,12 @@ static inline int pci_iov_bus_range(struct pci_bus *bus)
>  {
>  	return 0;
>  }
> +static inline void pci_iov_resource_set_size(struct pci_dev *dev, int resno,
> +					     resource_size_t size) { }
> +static inline bool pci_iov_is_memory_decoding_enabled(struct pci_dev *dev)
> +{
> +	return false;
> +}
>  static inline bool pci_resource_is_iov(int resno)
>  {
>  	return false;
> diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c
> index c6657cdd06f67..6cce3e19f22b0 100644
> --- a/drivers/pci/setup-res.c
> +++ b/drivers/pci/setup-res.c
> @@ -423,13 +423,39 @@ void pci_release_resource(struct pci_dev *dev, int resno)
>  }
>  EXPORT_SYMBOL(pci_release_resource);
>  
> +static bool pci_resize_is_memory_decoding_enabled(struct pci_dev *dev,
> +						  int resno)
> +{
> +	u16 cmd;
> +
> +	if (pci_resource_is_iov(resno))
> +		return pci_iov_is_memory_decoding_enabled(dev);
> +
> +	pci_read_config_word(dev, PCI_COMMAND, &cmd);
> +
> +	return cmd & PCI_COMMAND_MEMORY;
> +}
> +
> +static void pci_resize_resource_set_size(struct pci_dev *dev, int resno,
> +					 int size)
> +{
> +	resource_size_t res_size = pci_rebar_size_to_bytes(size);
> +	struct resource *res = dev->resource + resno;

pci_resource_n()

> +
> +	if (!pci_resource_is_iov(resno)) {
> +		resource_set_size(res, res_size);
> +	} else {
> +		resource_set_size(res, res_size * pci_sriov_get_totalvfs(dev));

Should this too be done in pci_iov_resource_set_size()? Why is it being 
done here?

> +		pci_iov_resource_set_size(dev, resno, res_size);
> +	}
> +}
> +
>  int pci_resize_resource(struct pci_dev *dev, int resno, int size)
>  {
>  	struct resource *res = pci_resource_n(dev, resno);
>  	struct pci_host_bridge *host;
>  	int old, ret;
>  	u32 sizes;
> -	u16 cmd;
>  
>  	/* Check if we must preserve the firmware's resource assignment */
>  	host = pci_find_host_bridge(dev->bus);
> @@ -440,8 +466,7 @@ int pci_resize_resource(struct pci_dev *dev, int resno, int size)
>  	if (!(res->flags & IORESOURCE_UNSET))
>  		return -EBUSY;
>  
> -	pci_read_config_word(dev, PCI_COMMAND, &cmd);
> -	if (cmd & PCI_COMMAND_MEMORY)
> +	if (pci_resize_is_memory_decoding_enabled(dev, resno))
>  		return -EBUSY;
>  
>  	sizes = pci_rebar_get_possible_sizes(dev, resno);
> @@ -459,7 +484,7 @@ int pci_resize_resource(struct pci_dev *dev, int resno, int size)
>  	if (ret)
>  		return ret;
>  
> -	resource_set_size(res, pci_rebar_size_to_bytes(size));
> +	pci_resize_resource_set_size(dev, resno, size);
>  
>  	/* Check if the new config works by trying to assign everything. */
>  	if (dev->bus->self) {
> @@ -471,7 +496,7 @@ int pci_resize_resource(struct pci_dev *dev, int resno, int size)
>  
>  error_resize:
>  	pci_rebar_set_size(dev, resno, old);
> -	resource_set_size(res, pci_rebar_size_to_bytes(old));
> +	pci_resize_resource_set_size(dev, resno, old);
>  	return ret;
>  }
>  EXPORT_SYMBOL(pci_resize_resource);
> 

-- 
 i.