On Wed, 2 Apr 2025, Michał Winiarski wrote:
> Drivers could leverage the fact that the VF BAR MMIO reservation is
> created for total number of VFs supported by the device by resizing the
> BAR to larger size when smaller number of VFs is enabled.
>
> Add a pci_iov_vf_bar_set_size() function to control the size and a
> pci_iov_vf_bar_get_sizes() helper to get the VF BAR sizes that will
> allow up to num_vfs to be successfully enabled with the current
> underlying reservation size.
>
> Signed-off-by: Michał Winiarski <michal.winiarski@xxxxxxxxx>
> ---
> drivers/pci/iov.c | 69 +++++++++++++++++++++++++++++++++++++++++++++
> include/linux/pci.h | 6 ++++
> 2 files changed, 75 insertions(+)
>
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 2fafbd6a998f0..8a62049b56b41 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -1313,3 +1313,72 @@ int pci_sriov_configure_simple(struct pci_dev *dev, int nr_virtfn)
> return nr_virtfn;
> }
> EXPORT_SYMBOL_GPL(pci_sriov_configure_simple);
> +
> +/**
> + * pci_iov_vf_bar_set_size - set a new size for a VF BAR
> + * @dev: the PCI device
> + * @resno: the resource number
> + * @size: new size as defined in the spec (0=1MB, 31=128TB)
> + *
> + * Set the new size of a VF BAR that supports VF resizable BAR capability.
> + * Unlike pci_resize_resource(), this does not cause the resource that
> + * reserves the MMIO space (originally up to total_VFs) to be resized, which
> + * means that following calls to pci_enable_sriov() can fail if the resources
> + * no longer fit.
> + *
> + * Return: 0 on success, or negative on failure.
> + */
> +int pci_iov_vf_bar_set_size(struct pci_dev *dev, int resno, int size)
> +{
> + int ret;
> + u32 sizes;
Please reverse the order of these variables.
> +
> + if (!pci_resource_is_iov(resno))
> + return -EINVAL;
> +
> + if (pci_iov_is_memory_decoding_enabled(dev))
> + return -EBUSY;
> +
> + sizes = pci_rebar_get_possible_sizes(dev, resno);
> + if (!sizes)
> + return -ENOTSUPP;
> +
> + if (!(sizes & BIT(size)))
Add include for BIT().
Although adding a helper like this would be helpful for multiple callers:
@@ -3780,6 +3780,88 @@ u32 pci_rebar_get_possible_sizes(struct pci_dev *pdev, int bar)
}
EXPORT_SYMBOL(pci_rebar_get_possible_sizes);
+/**
+ * pci_rebar_size_supported - check if size is supported for a resizable BAR
+ * @pdev: PCI device
+ * @bar: BAR to check
+ * @size: size as defined in the spec (0=1MB, 31=128TB)
+ *
+ * Return: %0 if @size is supported for @bar,
+ * %-EINVAL if @size is not supported,
+ * %-ENOTSUPP if @bar is not resizable.
+ */
+int pci_rebar_size_supported(struct pci_dev *pdev, int bar, int size)
+{
+ u64 sizes;
+
+ sizes = pci_rebar_get_possible_sizes(pdev, bar);
+ if (!sizes)
+ return -ENOTSUPP;
+
+ return BIT(size) & sizes ? 0 : -EINVAL;
+}
+EXPORT_SYMBOL_GPL(pci_rebar_size_supported);
(Yes, I've some rebar helpers pending so this is extract from that.)
> + return -EINVAL;
> +
> + ret = pci_rebar_set_size(dev, resno, size);
> + if (ret)
> + return ret;
> +
> + pci_iov_resource_set_size(dev, resno, pci_rebar_size_to_bytes(size));
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(pci_iov_vf_bar_set_size);
> +
> +/**
> + * pci_iov_vf_bar_get_sizes - get VF BAR sizes allowing to create up to num_vfs
> + * @dev: the PCI device
> + * @resno: the resource number
> + * @num_vfs: number of VFs
> + *
> + * Get the sizes of a VF resizable BAR that can accommodate @num_vfs within
> + * the currently assigned size of the resource @resno.
> + *
> + * Return: A bitmask of sizes in format defined in the spec (bit 0=1MB,
> + * bit 31=128TB).
> + */
> +u32 pci_iov_vf_bar_get_sizes(struct pci_dev *dev, int resno, int num_vfs)
> +{
> + resource_size_t vf_len = pci_resource_len(dev, resno);
> + u32 sizes;
> +
> + if (!num_vfs)
> + return 0;
> +
> + do_div(vf_len, num_vfs);
Add include for do_div().
> + sizes = (roundup_pow_of_two(vf_len + 1) - 1) >> ilog2(SZ_1M);
Doesn't resource_size() already do that + 1 so why is a second one needed
here?
Add include for ilog() and SZ_*.
> +
> + return sizes & pci_rebar_get_possible_sizes(dev, resno);
> +}
> +EXPORT_SYMBOL_GPL(pci_iov_vf_bar_get_sizes);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 0e8e3fd77e967..c8708f3749757 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -2389,6 +2389,8 @@ int pci_sriov_set_totalvfs(struct pci_dev *dev, u16 numvfs);
> int pci_sriov_get_totalvfs(struct pci_dev *dev);
> int pci_sriov_configure_simple(struct pci_dev *dev, int nr_virtfn);
> resource_size_t pci_iov_resource_size(struct pci_dev *dev, int resno);
> +int pci_iov_vf_bar_set_size(struct pci_dev *dev, int resno, int size);
> +u32 pci_iov_vf_bar_get_sizes(struct pci_dev *dev, int resno, int num_vfs);
> void pci_vf_drivers_autoprobe(struct pci_dev *dev, bool probe);
>
> /* Arch may override these (weak) */
> @@ -2441,6 +2443,10 @@ static inline int pci_sriov_get_totalvfs(struct pci_dev *dev)
> #define pci_sriov_configure_simple NULL
> static inline resource_size_t pci_iov_resource_size(struct pci_dev *dev, int resno)
> { return 0; }
> +static inline int pci_iov_vf_bar_set_size(struct pci_dev *dev, int resno, int size)
> +{ return -ENODEV; }
> +static inline u32 pci_iov_vf_bar_get_sizes(struct pci_dev *dev, int resno, int num_vfs)
> +{ return 0; }
> static inline void pci_vf_drivers_autoprobe(struct pci_dev *dev, bool probe) { }
> #endif
>
>
--
i.
