From aaca43fda742223e4f62bd73e13055f5364e9a9b Mon Sep 17 00:00:00 2001 From: Logan Gunthorpe Date: Mon, 30 Jul 2018 10:18:40 -0600 Subject: [PATCH] PCI: Add "pci=disable_acs_redir=" parameter for peer-to-peer support MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit To support peer-to-peer traffic on a segment of the PCI hierarchy, we must disable the ACS redirect bits for select PCI bridges. The bridges must be selected before the devices are discovered by the kernel and the IOMMU groups created. Therefore, add a kernel command line parameter to specify devices which must have their ACS bits disabled. The new parameter takes a list of devices separated by a semicolon. Each device specified will have its ACS redirect bits disabled. This is similar to the existing 'resource_alignment' parameter. The ACS Request P2P Request Redirect, P2P Completion Redirect and P2P Egress Control bits are disabled, which is sufficient to always allow passing P2P traffic uninterrupted. The bits are set after the kernel (optionally) enables the ACS bits itself. It is also done regardless of whether the kernel or platform firmware sets the bits. If the user tries to disable the ACS redirect for a device without the ACS capability, print a warning to dmesg. Signed-off-by: Logan Gunthorpe [bhelgaas: reorder to add the generic code first and move the device-specific quirk to subsequent patches] Signed-off-by: Bjorn Helgaas Reviewed-by: Stephen Bates Reviewed-by: Alex Williamson Acked-by: Christian König --- .../admin-guide/kernel-parameters.txt | 9 +++ drivers/pci/pci.c | 73 ++++++++++++++++++- 2 files changed, 80 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 4fa4c9ff04ae..d5c27d947c2e 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3192,6 +3192,15 @@ Adding the window is slightly risky (it may conflict with unreported devices), so this taints the kernel. + disable_acs_redir=[; ...] + Specify one or more PCI devices (in the format + specified above) separated by semicolons. + Each device specified will have the PCI ACS + redirect capabilities forced off which will + allow P2P traffic between devices through + bridges without forcing it upstream. Note: + this removes isolation between devices and + may put more devices in an IOMMU group. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power Management. diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index a6c38b15ac33..822577d9b39e 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -2982,6 +2982,63 @@ void pci_request_acs(void) pci_acs_enable = 1; } +static const char *disable_acs_redir_param; + +/** + * pci_disable_acs_redir - disable ACS redirect capabilities + * @dev: the PCI device + * + * For only devices specified in the disable_acs_redir parameter. + */ +static void pci_disable_acs_redir(struct pci_dev *dev) +{ + int ret = 0; + const char *p; + int pos; + u16 ctrl; + + if (!disable_acs_redir_param) + return; + + p = disable_acs_redir_param; + while (*p) { + ret = pci_dev_str_match(dev, p, &p); + if (ret < 0) { + pr_info_once("PCI: Can't parse disable_acs_redir parameter: %s\n", + disable_acs_redir_param); + + break; + } else if (ret == 1) { + /* Found a match */ + break; + } + + if (*p != ';' && *p != ',') { + /* End of param or invalid format */ + break; + } + p++; + } + + if (ret != 1) + return; + + pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS); + if (!pos) { + pci_warn(dev, "cannot disable ACS redirect for this hardware as it does not have ACS capabilities\n"); + return; + } + + pci_read_config_word(dev, pos + PCI_ACS_CTRL, &ctrl); + + /* P2P Request & Completion Redirect */ + ctrl &= ~(PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC); + + pci_write_config_word(dev, pos + PCI_ACS_CTRL, ctrl); + + pci_info(dev, "disabled ACS redirect\n"); +} + /** * pci_std_enable_acs - enable ACS on devices using standard ACS capabilites * @dev: the PCI device @@ -3021,12 +3078,22 @@ static void pci_std_enable_acs(struct pci_dev *dev) void pci_enable_acs(struct pci_dev *dev) { if (!pci_acs_enable) - return; + goto disable_acs_redir; if (!pci_dev_specific_enable_acs(dev)) - return; + goto disable_acs_redir; pci_std_enable_acs(dev); + +disable_acs_redir: + /* + * Note: pci_disable_acs_redir() must be called even if ACS was not + * enabled by the kernel because it may have been enabled by + * platform firmware. So if we are told to disable it, we should + * always disable it after setting the kernel's default + * preferences. + */ + pci_disable_acs_redir(dev); } static bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags) @@ -5966,6 +6033,8 @@ static int __init pci_setup(char *str) pcie_bus_config = PCIE_BUS_PEER2PEER; } else if (!strncmp(str, "pcie_scan_all", 13)) { pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS); + } else if (!strncmp(str, "disable_acs_redir=", 18)) { + disable_acs_redir_param = str + 18; } else { printk(KERN_ERR "PCI: Unknown option `%s'\n", str); -- GitLab