[+cc Logan]
On Wed, Jun 12, 2024 at 04:27:36AM -0700, Shivasharan S wrote:
> Update the p2p_dma_distance() to determine virtual inter-switch P2P links
> existing between two switches and use this to calculate the DMA distance
> between two devices.
>
> Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@xxxxxxxxxxxx>
> ---
> drivers/pci/Kconfig | 1 +
> drivers/pci/p2pdma.c | 18 +++++++++++++++++-
> 2 files changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
> index d35001589d88..3e6226ec91fd 100644
> --- a/drivers/pci/Kconfig
> +++ b/drivers/pci/Kconfig
> @@ -174,6 +174,7 @@ config PCI_P2PDMA
> depends on 64BIT
> select GENERIC_ALLOCATOR
> select NEED_SG_DMA_FLAGS
> + select PCI_SW_DISCOVERY
> help
> Enables drivers to do PCI peer-to-peer transactions to and from
> BARs that are exposed in other devices that are the part of
> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index 4f47a13cb500..780e649b3a1d 100644
> --- a/drivers/pci/p2pdma.c
> +++ b/drivers/pci/p2pdma.c
> @@ -21,6 +21,8 @@
> #include <linux/seq_buf.h>
> #include <linux/xarray.h>
>
> +extern bool sw_disc_check_virtual_link(struct pci_dev *a, struct pci_dev *b);
This isn't the way we declare external references. Probably
drivers/pci/pci.h. Would need a "pci_" or "pcie_" prefix.
> struct pci_p2pdma {
> struct gen_pool *pool;
> bool p2pmem_published;
> @@ -576,7 +578,7 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
> int *dist, bool verbose)
> {
> enum pci_p2pdma_map_type map_type = PCI_P2PDMA_MAP_THRU_HOST_BRIDGE;
> - struct pci_dev *a = provider, *b = client, *bb;
> + struct pci_dev *a = provider, *b = client, *bb, *b_virtual_link = NULL;
> bool acs_redirects = false;
> struct pci_p2pdma *p2pdma;
> struct seq_buf acs_list;
> @@ -606,6 +608,17 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
> if (a == bb)
> goto check_b_path_acs;
>
> + // Physical Broadcom PEX switches can be provisioned into
> + // multiple virtual switches.
> + // if both upstream bridges belong to the same physical
> + // switch, and the switch supports P2P,
> + // p2p_dma_distance() should take into account of such
> + // scenarios.
Copy the comment style (/* */) of the rest of the file. Rewrap to fit
in 80 columns like the rest of the file. Capitalize sentences. Add
blank line between paragraphs.
> + if (sw_disc_check_virtual_link(a, bb)) {
> + b_virtual_link = bb;
> + goto check_b_path_acs;
> + }
> +
> bb = pci_upstream_bridge(bb);
> dist_b++;
> }
> @@ -629,6 +642,9 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
> acs_cnt++;
> }
>
> + if (b_virtual_link && bb == b_virtual_link)
> + break;
> +
> bb = pci_upstream_bridge(bb);
> }
>
> --
> 2.43.0
>
