[PATCH v3 11/11] PCI: Check ACS Extended flags for pci_bus_isolated()

[Jason Gunthorpe <jgg@nvidia.com>]

When looking at a PCIe switch we want to see that the USP/DSP MMIO have
request redirect enabled. Detect the case where the USP is expressly not
isolated from the DSP and ensure the USP is included in the group.

The DSP Memory Target also applies to the Root Port, check it there
too. If upstream directed transactions can reach the root port MMIO then
it is not isolated.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/pci/search.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index dac6b042fd5f5d..cba417cbe3476e 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -127,6 +127,8 @@ static enum pci_bus_isolation pcie_switch_isolated(struct pci_bus *bus)
 	 * traffic flowing upstream back downstream through another DSP.
 	 *
 	 * Thus any non-permissive DSP spoils the whole bus.
+	 * PCI_ACS_UNCLAIMED_RR is not required since rejecting requests with
+	 * error is still isolation.
 	 */
 	guard(rwsem_read)(&pci_bus_sem);
 	list_for_each_entry(pdev, &bus->devices, bus_list) {
@@ -136,8 +138,14 @@ static enum pci_bus_isolation pcie_switch_isolated(struct pci_bus *bus)
 		    pdev->dma_alias_mask)
 			return PCIE_NON_ISOLATED;
 
-		if (!pci_acs_enabled(pdev, PCI_ACS_ISOLATED))
+		if (!pci_acs_enabled(pdev, PCI_ACS_ISOLATED |
+						   PCI_ACS_DSP_MT_RR |
+						   PCI_ACS_USP_MT_RR)) {
+			/* The USP is isolated from the DSP */
+			if (!pci_acs_enabled(pdev, PCI_ACS_USP_MT_RR))
+				return PCIE_NON_ISOLATED;
 			return PCIE_SWITCH_DSP_NON_ISOLATED;
+		}
 	}
 	return PCIE_ISOLATED;
 }
@@ -232,11 +240,13 @@ enum pci_bus_isolation pci_bus_isolated(struct pci_bus *bus)
 	/*
 	 * Since PCIe links are point to point root ports are isolated if there
 	 * is no internal loopback to the root port's MMIO. Like MFDs assume if
-	 * there is no ACS cap then there is no loopback.
+	 * there is no ACS cap then there is no loopback. The root port uses
+	 * DSP_MT_RR for its own MMIO.
 	 */
 	case PCI_EXP_TYPE_ROOT_PORT:
 		if (bridge->acs_cap &&
-		    !pci_acs_enabled(bridge, PCI_ACS_ISOLATED))
+		    !pci_acs_enabled(bridge,
+				     PCI_ACS_ISOLATED | PCI_ACS_DSP_MT_RR))
 			return PCIE_NON_ISOLATED;
 		return PCIE_ISOLATED;
 
-- 
2.43.0