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Wed, 12 Jun 2024 04:38:16 -0700 (PDT) From: Shivasharan S To: linux-pci@vger.kernel.org, bhelgaas@google.com Cc: linux-kernel@vger.kernel.org, sumanesh.samanta@broadcom.com, sathya.prakash@broadcom.com, Shivasharan S Subject: [PATCH 1/2] switch_discovery: Add new module to discover inter switch links between PCI-to-PCI bridges Date: Wed, 12 Jun 2024 04:27:35 -0700 Message-Id: <1718191656-32714-2-git-send-email-shivasharan.srikanteshwara@broadcom.com> X-Mailer: git-send-email 2.4.3 In-Reply-To: <1718191656-32714-1-git-send-email-shivasharan.srikanteshwara@broadcom.com> References: <1718191656-32714-1-git-send-email-shivasharan.srikanteshwara@broadcom.com> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This kernel module discovers the virtual inter-switch P2P links present between two PCI-to-PCI bridges that allows an optimal data path for data movement. The module creates sysfs entries for upstream PCI-to-PCI bridges which supports the inter switch P2P links as below: Host root bridge --------------------------------------- | | NIC1 --- PCI Switch1 --- Inter-switch link --- PCI Switch2 --- NIC2 (af:00.0) (ad:00.0) (8b:00.0) (8d:00.0) | | GPU1 GPU2 (b0:00.0) (8e:00.0) SERVER 1 /sys/kernel/pci_switch_link/virtual_switch_links ├── 0000:8b:00.0 │   └── 0000:ad:00.0 -> ../0000:ad:00.0 └── 0000:ad:00.0 └── 0000:8b:00.0 -> ../0000:8b:00.0 Signed-off-by: Shivasharan S Signed-off-by: Sumanesh Samanta --- .../driver-api/pci/switch_discovery.rst | 52 +++ MAINTAINERS | 13 + drivers/pci/switch/Kconfig | 9 + drivers/pci/switch/Makefile | 1 + drivers/pci/switch/switch_discovery.c | 375 ++++++++++++++++++ drivers/pci/switch/switch_discovery.h | 44 ++ 6 files changed, 494 insertions(+) create mode 100644 Documentation/driver-api/pci/switch_discovery.rst create mode 100644 drivers/pci/switch/switch_discovery.c create mode 100644 drivers/pci/switch/switch_discovery.h diff --git a/Documentation/driver-api/pci/switch_discovery.rst b/Documentation/driver-api/pci/switch_discovery.rst new file mode 100644 index 000000000000..7c1476260e5e --- /dev/null +++ b/Documentation/driver-api/pci/switch_discovery.rst @@ -0,0 +1,52 @@ +================================= +Linux PCI Switch discovery module +================================= + +Modern PCI switches support inter switch Peer-to-Peer(P2P) data transfer +without using host resources. For example, Broadcom(PLX) PCIe Switches have a +capability where a single physical switch can be divided up into multiple +virtual switches at SOD. PCIe switch discovery module detects the virtual links +between the switches that belong to the same physical switch. +This allows user space applications to discover these virtual links that belong +to the same physical switch and configure optimized data paths. + +Userspace Interface +=================== + +The module exposes sysfs entries for user space applications like MPI, NCCL, +UCC, RCCL, HCCL, etc to discover the virtual switch links. + +Consider the below topology + + Host root bridge + --------------------------------------- + | | + NIC1 --- PCI Switch1 --- Inter-switch link --- PCI Switch2 --- NIC2 +(af:00.0) (ad:00.0) (8b:00.0) (8d:00.0) + | | + GPU1 GPU2 + (b0:00.0) (8e:00.0) + SERVER 1 + +The simple topology above shows SERVER1, has Switch1 and Switch2 which are +virtual switches that belong to the same physical switch that support +Inter switch P2P. +Switch1 and Switch2 have a GPU and NIC each connected. +The module will detect the virtual P2P link existing between the two switches +and create the sysfs entries as below. + +/sys/kernel/pci_switch_link/virtual_switch_links +├── 0000:8b:00.0 +│   └── 0000:ad:00.0 -> ../0000:ad:00.0 +└── 0000:ad:00.0 + └── 0000:8b:00.0 -> ../0000:8b:00.0 + +The HPC/AI libraries that analyze the topology can decide the optimal data +path like: NIC1->GPU1->GPU2->NIC1 which would have otherwise take a +non-optimal path like NIC1->GPU1->GPU2->GPU1->NIC1. + +Enable P2P DMA to discover virtual links +---------------------------------------- +The module also enhances :c:func:`pci_p2pdma_distance()` to determine a virtual +link between the upstream PCI-to-PCI bridges of the devices and detect optimal +path for applications using P2P DMA API. diff --git a/MAINTAINERS b/MAINTAINERS index 823387766a0c..b1bf3533ea6f 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -17359,6 +17359,19 @@ F: Documentation/driver-api/pci/p2pdma.rst F: drivers/pci/p2pdma.c F: include/linux/pci-p2pdma.h +PCI SWITCH DISCOVERY +M: Shivasharan S +M: Sumanesh Samanta +L: linux-pci@vger.kernel.org +S: Maintained +Q: https://patchwork.kernel.org/project/linux-pci/list/ +B: https://bugzilla.kernel.org +C: irc://irc.oftc.net/linux-pci +T: git git://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git +F: Documentation/driver-api/pci/switch_discovery.rst +F: drivers/pci/switch/switch_discovery.c +F: drivers/pci/switch/switch_discovery.h + PCI SUBSYSTEM M: Bjorn Helgaas L: linux-pci@vger.kernel.org diff --git a/drivers/pci/switch/Kconfig b/drivers/pci/switch/Kconfig index d370f4ce0492..fb4410153950 100644 --- a/drivers/pci/switch/Kconfig +++ b/drivers/pci/switch/Kconfig @@ -12,4 +12,13 @@ config PCI_SW_SWITCHTEC devices. See for more information. +config PCI_SW_DISCOVERY + depends on PCI + tristate "PCI Switch discovery module" + help + This kernel module discovers the PCI-to-PCI bridges of PCIe switches + and forms the virtual switch links if the bridges belong to the same + Physical switch. The switch links help to identify shorter distances + for P2P configurations. + endmenu diff --git a/drivers/pci/switch/Makefile b/drivers/pci/switch/Makefile index acd56d3b4a35..a3584b5146af 100644 --- a/drivers/pci/switch/Makefile +++ b/drivers/pci/switch/Makefile @@ -1,2 +1,3 @@ # SPDX-License-Identifier: GPL-2.0 obj-$(CONFIG_PCI_SW_SWITCHTEC) += switchtec.o +obj-$(CONFIG_PCI_SW_DISCOVERY) += switch_discovery.o diff --git a/drivers/pci/switch/switch_discovery.c b/drivers/pci/switch/switch_discovery.c new file mode 100644 index 000000000000..a427d3885b1f --- /dev/null +++ b/drivers/pci/switch/switch_discovery.c @@ -0,0 +1,375 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * PCI Switch Discovery module + * + * Copyright (c) 2024 Broadcom Inc. + * + * Authors: Broadcom Inc. + * Sumanesh Samanta + * Shivasharan S + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include +#include +#include +#include +#include "switch_discovery.h" + +static DECLARE_RWSEM(sw_disc_rwlock); +static struct kobject *sw_disc_kobj, *sw_link_kobj; +static struct kobject *sw_kobj[SWD_MAX_VIRT_SWITCH]; +static DECLARE_BITMAP(swdata_valid, SWD_MAX_VIRT_SWITCH); + +static struct switch_data *swdata; + +static int sw_disc_probe(void); +static int sw_disc_create_sysfs_files(void); +static bool brcm_sw_is_p2p_supported(struct pci_dev *pdev, char *serial_num); + +static inline bool sw_disc_is_supported_pdev(struct pci_dev *pdev) +{ + if ((pdev->vendor == PCI_VENDOR_ID_LSI) && + ((pdev->device == PCI_DEVICE_ID_BRCM_PEX_89000_HLC) || + (pdev->device == PCI_DEVICE_ID_BRCM_PEX_89000_LLC))) + return true; + + return false; +} + +static ssize_t sw_disc_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) +{ + int retval; + + down_write(&sw_disc_rwlock); + retval = sw_disc_probe(); + if (!retval) { + pr_debug("No new switch found\n"); + goto exit_success; + } + + retval = sw_disc_create_sysfs_files(); + if (retval < 0) { + pr_err("Failed to create the sysfs entries, retval %d\n", + retval); + } + +exit_success: + up_write(&sw_disc_rwlock); + return sysfs_emit(buf, SWD_SCAN_DONE); +} + +/* This function probes the PCIe devices for virtual links */ +static int sw_disc_probe(void) +{ + int i, bit; + struct pci_dev *pdev = NULL; + int topology_changed = 0; + DECLARE_BITMAP(sw_found_map, SWD_MAX_VIRT_SWITCH); + + while ((pdev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, pdev)) != NULL) { + int sw_found; + + /* Currently this function only traverses Broadcom + * PEX switches and determines the virtual SW links. + * Other Switch vendors can add their specific logic + * determine the virtual links. + */ + if (!sw_disc_is_supported_pdev(pdev)) + continue; + + sw_found = -1; + + for_each_set_bit(bit, swdata_valid, SWD_MAX_VIRT_SWITCH) { + if (swdata[bit].devfn == pdev->devfn && + swdata[bit].bus == pdev->bus) { + sw_found = bit; + set_bit(sw_found, sw_found_map); + break; + } + } + + if (sw_found != -1) + continue; + + for (i = 0; i < SWD_MAX_VIRT_SWITCH; i++) + if (!swdata[i].bus) + break; + + if (i >= SWD_MAX_VIRT_SWITCH) { + pr_err("Max switch exceeded\n"); + break; + } + + sw_found = i; + + if (!brcm_sw_is_p2p_supported(pdev, (char *)&swdata[sw_found].serial_num)) + continue; + + /* Found a new switch which supports P2P */ + swdata[sw_found].devfn = pdev->devfn; + swdata[sw_found].bus = pdev->bus; + + topology_changed = 1; + set_bit(sw_found, sw_found_map); + set_bit(sw_found, swdata_valid); + } + + /* handle device removal */ + for_each_clear_bit(bit, sw_found_map, SWD_MAX_VIRT_SWITCH) { + if (test_bit(bit, swdata_valid)) { + memset(&swdata[bit], 0, sizeof(swdata[i])); + clear_bit(bit, swdata_valid); + topology_changed = 1; + } + } + + return topology_changed; +} + +/* Check the various config space registers of the Broadcom PCI device and + * return true if the device supports inter switch P2P. + * If P2P is supported, return the device serial number back to + * caller. + */ +bool brcm_sw_is_p2p_supported(struct pci_dev *pdev, char *serial_num) +{ + int base; + u32 cap_data1, cap_data2; + u16 vsec; + u32 vsec_data; + + base = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_DSN); + if (!base) { + pr_debug("Failed to get extended capability bus %x devfn %x\n", + pdev->bus->number, pdev->devfn); + return false; + } + + vsec = pci_find_vsec_capability(pdev, PCI_VENDOR_ID_LSI, 1); + if (!vsec) { + pr_debug("Failed to get VSEC bus %x devfn %x\n", + pdev->bus->number, pdev->devfn); + return false; + } + + if (pci_pcie_type(pdev) != PCI_EXP_TYPE_UPSTREAM) + return false; + + pci_read_config_dword(pdev, base + 8, &cap_data1); + pci_read_config_dword(pdev, base + 4, &cap_data2); + + pci_read_config_dword(pdev, vsec + 12, &vsec_data); + + pr_debug("Found Broadcom device bus 0x%x devfn 0x%x " + "Serial Number: 0x%x 0x%x, VSEC 0x%x\n", + pdev->bus->number, pdev->devfn, + cap_data1, cap_data2, vsec_data); + + if (!SECURE_PART(cap_data1)) + return false; + + if (!(P2PMASK(vsec_data) & INTER_SWITCH_LINK)) + return false; + + if (serial_num) + snprintf(serial_num, SWD_MAX_CHAR, "%x%x", cap_data1, cap_data2); + + return true; +} + +static int sw_disc_create_sysfs_files(void) +{ + int i, j, retval; + + for (i = 0; i < SWD_MAX_VIRT_SWITCH; i++) { + if (sw_kobj[i]) { + kobject_put(sw_kobj[i]); + sw_kobj[i] = NULL; + } + } + + if (sw_link_kobj) { + kobject_put(sw_link_kobj); + sw_link_kobj = NULL; + } + + sw_link_kobj = kobject_create_and_add(SWD_LINK_DIR_STRING, sw_disc_kobj); + if (!sw_link_kobj) { + pr_err("Failed to create pci link object\n"); + return -ENOMEM; + } + + for (i = 0; i < SWD_MAX_VIRT_SWITCH; i++) { + int segment, bus, device, function; + char bdf_i[SWD_MAX_CHAR]; + + if (!test_bit(i, swdata_valid)) + continue; + + segment = pci_domain_nr(swdata[i].bus); + bus = swdata[i].bus->number; + device = pci_ari_enabled(swdata[i].bus) ? + 0 : PCI_SLOT(swdata[i].devfn); + function = pci_ari_enabled(swdata[i].bus) ? + swdata[i].devfn : PCI_FUNC(swdata[i].devfn); + sprintf(bdf_i, "%04x:%02x:%02x.%x", + segment, bus, device, function); + + for (j = i + 1; j < SWD_MAX_VIRT_SWITCH; j++) { + char bdf_j[SWD_MAX_CHAR]; + + if (!test_bit(j, swdata_valid)) + continue; + segment = pci_domain_nr(swdata[j].bus); + bus = swdata[j].bus->number; + device = pci_ari_enabled(swdata[j].bus) ? + 0 : PCI_SLOT(swdata[j].devfn); + function = pci_ari_enabled(swdata[j].bus) ? + swdata[j].devfn : PCI_FUNC(swdata[j].devfn); + sprintf(bdf_j, "%04x:%02x:%02x.%x", + segment, bus, device, function); + + if (strcmp(swdata[i].serial_num, swdata[j].serial_num) == 0) { + if (!sw_kobj[i]) { + sw_kobj[i] = kobject_create_and_add(bdf_i, + sw_link_kobj); + if (!sw_kobj[i]) { + pr_err("Failed to create sysfs entry for switch %s\n", + bdf_i); + } + } + + if (!sw_kobj[j]) { + sw_kobj[j] = kobject_create_and_add(bdf_j, + sw_link_kobj); + if (!sw_kobj[j]) { + pr_err("Failed to create sysfs entry for switch %s\n", + bdf_j); + } + } + + retval = sysfs_create_link(sw_kobj[i], sw_kobj[j], bdf_j); + if (retval) + pr_err("Error creating symlink %s and %s\n", + bdf_i, bdf_j); + + retval = sysfs_create_link(sw_kobj[j], sw_kobj[i], bdf_i); + if (retval) + pr_err("Error creating symlink %s and %s\n", + bdf_j, bdf_i); + } + } + } + + return 0; +} + +/* + * Check if the two pci devices have virtual P2P link available. + * This function is used by the p2pdma to determine virtual + * links between the PCI-to-PCI bridges + */ +bool sw_disc_check_virtual_link(struct pci_dev *a, + struct pci_dev *b) +{ + char serial_num_a[SWD_MAX_CHAR], serial_num_b[SWD_MAX_CHAR]; + + /* + * Check if the PCIe devices support Virtual P2P links + */ + if (!sw_disc_is_supported_pdev(a)) + return false; + + if (!sw_disc_is_supported_pdev(b)) + return false; + + if (brcm_sw_is_p2p_supported(a, serial_num_a) && + brcm_sw_is_p2p_supported(b, serial_num_b)) + if (!strcmp(serial_num_a, serial_num_b)) + return true; + + return false; +} +EXPORT_SYMBOL_GPL(sw_disc_check_virtual_link); + +static struct kobj_attribute sw_disc_attribute = + __ATTR(SWD_FILE_NAME_STRING, 0444, sw_disc_show, NULL); + +// Create attribute group +static struct attribute *attrs[] = { + &sw_disc_attribute.attr, + NULL, +}; + +static struct attribute_group attr_group = { + .attrs = attrs, +}; + +static int __init sw_discovery_init(void) +{ + int i, retval; + + for (i = 0; i < SWD_MAX_VIRT_SWITCH; i++) + sw_kobj[i] = NULL; + + // Create "sw_disc" kobject + sw_disc_kobj = kobject_create_and_add(SWD_DIR_STRING, kernel_kobj); + if (!sw_disc_kobj) { + pr_err("Failed to create sw_disc_kobj\n"); + return -ENOMEM; + } + + retval = sysfs_create_group(sw_disc_kobj, &attr_group); + if (retval) { + pr_err("Cannot register sysfs attribute group\n"); + kobject_put(sw_disc_kobj); + } + + swdata = kzalloc(sizeof(swdata) * SWD_MAX_VIRT_SWITCH, GFP_KERNEL); + if (!swdata) { + sysfs_remove_group(sw_disc_kobj, &attr_group); + kobject_put(sw_disc_kobj); + return 0; + } + + pr_info("Loading PCIe switch discovery module, version %s\n", + SWITCH_DISC_VERSION); + + return 0; +} + +static void __exit sw_discovery_exit(void) +{ + int i; + + if (!swdata) + kfree(swdata); + + for (i = 0; i < SWD_MAX_VIRT_SWITCH; i++) { + if (sw_kobj[i]) + kobject_put(sw_kobj[i]); + } + + // Remove kobject + if (sw_link_kobj) + kobject_put(sw_link_kobj); + + sysfs_remove_group(sw_disc_kobj, &attr_group); + kobject_put(sw_disc_kobj); +} + +module_init(sw_discovery_init); +module_exit(sw_discovery_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Broadcom Inc."); +MODULE_VERSION(SWITCH_DISC_VERSION); +MODULE_DESCRIPTION("PCIe Switch Discovery Module"); diff --git a/drivers/pci/switch/switch_discovery.h b/drivers/pci/switch/switch_discovery.h new file mode 100644 index 000000000000..b84f5d2e29ac --- /dev/null +++ b/drivers/pci/switch/switch_discovery.h @@ -0,0 +1,44 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * PCI Switch Discovery module + * + * Copyright (c) 2024 Broadcom Inc. + * + * Authors: Broadcom Inc. + * Sumanesh Samanta + * Shivasharan S + */ + +#ifndef PCI_SWITCH_DISC_H +#define PCI_SWITCH_DISC_H + +#define SWD_MAX_SWITCH 32 +#define SWD_MAX_VER_PER_SWITCH 8 + +#define SWD_MAX_VIRT_SWITCH (SWD_MAX_SWITCH * SWD_MAX_VER_PER_SWITCH) +#define SWD_MAX_CHAR 16 +#define SWITCH_DISC_VERSION "0.1.1" +#define SWD_DIR_STRING "pci_switch_link" +#define SWD_LINK_DIR_STRING "virtual_switch_links" +#define SWD_SCAN_DONE "done\n" + +#define SWD_FILE_NAME_STRING refresh_switch_toplogy + +/* Broadcom Vendor Specific definitions */ +#define PCI_VENDOR_ID_LSI 0x1000 +#define PCI_DEVICE_ID_BRCM_PEX_89000_HLC 0xC030 +#define PCI_DEVICE_ID_BRCM_PEX_89000_LLC 0xC034 + +#define P2PMASK(x) (((x) & 0x300) >> 8) +#define SECURE_PART(x) ((x) & 0x8) +#define INTER_SWITCH_LINK 0x2 + +struct switch_data { + int devfn; + struct pci_bus *bus; + char serial_num[SWD_MAX_CHAR]; +}; + +bool sw_disc_check_virtual_link(struct pci_dev *a, struct pci_dev *b); + +#endif /* PCI_SWITCH_DISC_H */ From patchwork Wed Jun 12 11:27:36 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shivasharan S X-Patchwork-Id: 1946812 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=broadcom.com header.i=@broadcom.com header.a=rsa-sha256 header.s=google header.b=KaZm++LC; dkim-atps=neutral Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=2604:1380:45d1:ec00::1; helo=ny.mirrors.kernel.org; envelope-from=linux-pci+bounces-8666-incoming=patchwork.ozlabs.org@vger.kernel.org; receiver=patchwork.ozlabs.org) Received: from ny.mirrors.kernel.org (ny.mirrors.kernel.org [IPv6:2604:1380:45d1:ec00::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (secp384r1)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4Vzk840X97z20KL for ; 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Wed, 12 Jun 2024 04:38:19 -0700 (PDT) From: Shivasharan S To: linux-pci@vger.kernel.org, bhelgaas@google.com Cc: linux-kernel@vger.kernel.org, sumanesh.samanta@broadcom.com, sathya.prakash@broadcom.com, Shivasharan S Subject: [PATCH 2/2] pci/p2pdma: Modify p2p_dma_distance to detect virtual P2P links Date: Wed, 12 Jun 2024 04:27:36 -0700 Message-Id: <1718191656-32714-3-git-send-email-shivasharan.srikanteshwara@broadcom.com> X-Mailer: git-send-email 2.4.3 In-Reply-To: <1718191656-32714-1-git-send-email-shivasharan.srikanteshwara@broadcom.com> References: <1718191656-32714-1-git-send-email-shivasharan.srikanteshwara@broadcom.com> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 --- 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 #include +extern bool sw_disc_check_virtual_link(struct pci_dev *a, struct pci_dev *b); + 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. + 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); }