Re: [PATCH v3 3/5] PCI: Allow IOV resources to be resized in pci_resize_resource

[Ilpo Järvinen]

On Thu, 10 Oct 2024, 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. See PCIe r4.0, sec 9.3.7.4.
> 
> Signed-off-by: Michał Winiarski <michal.winiarski@xxxxxxxxx>
> ---
>  drivers/pci/iov.c       | 20 ++++++++++++++++++++
>  drivers/pci/pci.c       |  9 ++++++++-
>  drivers/pci/pci.h       |  8 ++++++++
>  drivers/pci/setup-res.c | 33 ++++++++++++++++++++++++++++-----
>  4 files changed, 64 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index fd5c059b29c13..591a3eae1618a 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -154,6 +154,26 @@ resource_size_t pci_iov_resource_size(struct pci_dev *dev, int resno)
>  	return dev->sriov->barsz[resno - PCI_IOV_RESOURCES];
>  }
>  
> +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[resno - PCI_IOV_RESOURCES] = 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 7d85c04fbba2a..788ae61731213 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -3718,10 +3718,17 @@ void pci_acs_init(struct pci_dev *dev)
>   */
>  static int pci_rebar_find_pos(struct pci_dev *pdev, int bar)
>  {
> +	int cap = PCI_EXT_CAP_ID_REBAR;
>  	unsigned int pos, nbars, i;
>  	u32 ctrl;
>  
> -	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_REBAR);
> +#ifdef CONFIG_PCI_IOV
> +	if (pci_resource_is_iov(bar)) {
> +		cap = PCI_EXT_CAP_ID_VF_REBAR;
> +		bar -= PCI_IOV_RESOURCES;
> +	}
> +#endif

Perhaps abstracting bar -= PCI_IOV_RESOURCES too into some static inline 
function would be useful so you could drop the ifdefs. That calculation 
seems to be done in few places besides this one.

> +	pos = pci_find_ext_capability(pdev, cap);
>  	if (!pos)
>  		return -ENOTSUPP;
>  
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index c55f2d7a4f37e..e15fd8fe0f81f 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -584,6 +584,8 @@ static inline bool pci_resource_is_iov(int resno)
>  {
>  	return resno >= PCI_IOV_RESOURCES && resno <= PCI_IOV_RESOURCE_END;
>  }
> +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);
>  extern const struct attribute_group sriov_pf_dev_attr_group;
>  extern const struct attribute_group sriov_vf_dev_attr_group;
>  #else
> @@ -607,6 +609,12 @@ static inline bool pci_resource_is_iov(int resno)
>  {
>  	return false;
>  }
> +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;
> +}
>  #endif /* CONFIG_PCI_IOV */
>  
>  #ifdef CONFIG_PCIE_PTM
> diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c
> index e2cf79253ebda..95a13a5fa379c 100644
> --- a/drivers/pci/setup-res.c
> +++ b/drivers/pci/setup-res.c
> @@ -425,13 +425,37 @@ 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;
> +
> +	if (!pci_resource_is_iov(resno)) {
> +		res->end = res->start + res_size - 1;
> +	} else {
> +		res->end = res->start + res_size * pci_sriov_get_totalvfs(dev) - 1;

I wish Bjorn would pick up my resource_set_{range,size}() series [1] so we 
wouldn't need to open-code this resource size calculation everywhere.

> +		pci_iov_resource_set_size(dev, resno, res_size);
> +	}
> +}
> +
>  int pci_resize_resource(struct pci_dev *dev, int resno, int size)
>  {
>  	struct resource *res = dev->resource + 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);
> @@ -442,8 +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);
> @@ -461,7 +484,7 @@ int pci_resize_resource(struct pci_dev *dev, int resno, int size)
>  	if (ret)
>  		return ret;
>  
> -	res->end = res->start + pci_rebar_size_to_bytes(size) - 1;
> +	pci_resize_resource_set_size(dev, resno, size);
>  
>  	/* Check if the new config works by trying to assign everything. */
>  	if (dev->bus->self) {
> @@ -473,7 +496,7 @@ int pci_resize_resource(struct pci_dev *dev, int resno, int size)
>  
>  error_resize:
>  	pci_rebar_set_size(dev, resno, old);
> -	res->end = res->start + pci_rebar_size_to_bytes(old) - 1;
> +	pci_resize_resource_set_size(dev, resno, old);
>  	return ret;
>  }
>  EXPORT_SYMBOL(pci_resize_resource);
> 

[1] https://patchwork.kernel.org/project/linux-pci/patch/20240614100606.15830-2-ilpo.jarvinen@xxxxxxxxxxxxxxx/

-- 
 i.