[PATCH 6.0 0644/1073] PCI: vmd: Fix secondary bus reset for Intel bridges

Greg Kroah-Hartman
2022-12-28T16:20:45Z

From: Francisco Munoz <francisco.munoz.ruiz@linux.intel.com>

[ Upstream commit 0a584655ef89541dae4d48d2c523b1480ae80284 ]

The reset was never applied in the current implementation because Intel
Bridges owned by VMD are parentless. Internally, pci_reset_bus() applies
a reset to the parent of the PCI device supplied as argument, but in this
case it failed because there wasn't a parent.

In more detail, this change allows the VMD driver to enumerate NVMe devices
in pass-through configurations when guest reboots are performed. There was
an attempted to fix this, but later we discovered that the code inside
pci_reset_bus() wasn’t triggering secondary bus resets. Therefore, we
updated the parameters passed to it, and now NVMe SSDs attached to VMD
bridges are properly enumerated in VT-d pass-through scenarios.

Link: https://lore.kernel.org/r/20221206001637.4744-1-francisco.munoz.ruiz@linux.intel.com
Fixes: 6aab5622296b ("PCI: vmd: Clean up domain before enumeration")
Signed-off-by: Francisco Munoz <francisco.munoz.ruiz@linux.intel.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Nirmal Patel <nirmal.patel@linux.intel.com>
Reviewed-by: Jonathan Derrick <jonathan.derrick@linux.dev>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/pci/controller/vmd.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
index 98e0746e681c..769eedeb8802 100644
--- a/drivers/pci/controller/vmd.c
+++ b/drivers/pci/controller/vmd.c
@@ -719,6 +719,7 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
resource_size_t offset[2] = {0};
resource_size_t membar2_offset = 0x2000;
struct pci_bus *child;
+ struct pci_dev *dev;
int ret;

/*
@@ -859,8 +860,25 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)

pci_scan_child_bus(vmd->bus);
vmd_domain_reset(vmd);
- list_for_each_entry(child, &vmd->bus->children, node)
- pci_reset_bus(child->self);
+
+ /* When Intel VMD is enabled, the OS does not discover the Root Ports
+ * owned by Intel VMD within the MMCFG space. pci_reset_bus() applies
+ * a reset to the parent of the PCI device supplied as argument. This
+ * is why we pass a child device, so the reset can be triggered at
+ * the Intel bridge level and propagated to all the children in the
+ * hierarchy.
+ */
+ list_for_each_entry(child, &vmd->bus->children, node) {
+ if (!list_empty(&child->devices)) {
+ dev = list_first_entry(&child->devices,
+ struct pci_dev, bus_list);
+ if (pci_reset_bus(dev))
+ pci_warn(dev, "can't reset device: %d\n", ret);
+
+ break;
+ }
+ }
+
pci_assign_unassigned_bus_resources(vmd->bus);

/*
--
2.35.1