[PATCH 1/1] PCI: vmd: Fix boot failure when trying to clean up domain before enumeration

[Adrian Huang <adrianhuang0701@gmail.com>]

From: Adrian Huang <ahuang12@lenovo.com>

Commit 6aab5622296b ("PCI: vmd: Clean up domain before enumeration")
clears PCI configuration space of VMD root ports. However, the host OS
cannot boot successfully with the following error message:

  vmd 0000:64:05.5: PCI host bridge to bus 10000:00
  ...
  vmd 0000:64:05.5: Bound to PCI domain 10000
  ...
  DMAR: VT-d detected Invalidation Queue Error: Reason f
  DMAR: VT-d detected Invalidation Time-out Error: SID ffff
  DMAR: VT-d detected Invalidation Completion Error: SID ffff
  DMAR: QI HEAD: UNKNOWN qw0 = 0x0, qw1 = 0x0
  DMAR: QI PRIOR: UNKNOWN qw0 = 0x0, qw1 = 0x0
  DMAR: Invalidation Time-out Error (ITE) cleared

The root cause is that memset_io() clears prefetchable memory base/limit
registers and prefetchable base/limit 32 bits registers sequentially. This
might enable prefetchable memory if the device disables prefetchable memory
originally. Here is an example (before memset_io()):

  PCI configuration space for 10000:00:00.0:
  86 80 30 20 06 00 10 00 04 00 04 06 00 00 01 00
  00 00 00 00 00 00 00 00 00 01 01 00 00 00 00 20
  00 00 00 00 01 00 01 00 ff ff ff ff 75 05 00 00
  00 00 00 00 40 00 00 00 00 00 00 00 00 01 02 00

So, prefetchable memory is ffffffff00000000-575000fffff, which is disabled.
Here is the quote from section 7.5.1.3.9 of PCI Express Base 6.0 spec:

  The Prefetchable Memory Limit register must be programmed to a smaller
  value than the Prefetchable Memory Base register if there is no
  prefetchable memory on the secondary side of the bridge.

When memset_io() clears prefetchable base 32 bits register, the
prefetchable memory becomes 0000000000000000-575000fffff, which is enabled.
This behavior causes that the content of PCI configuration space of VMD
root ports is 0xff after invoking memset_io() in vmd_domain_reset():

  10000:00:00.0 PCI bridge: Intel Corporation Sky Lake-E PCI Express Root Port A (rev ff) (prog-if ff)
          !!! Unknown header type 7f
  00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
  ...
  f0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

  10000:00:01.0 PCI bridge: Intel Corporation Sky Lake-E PCI Express Root Port B (rev ff) (prog-if ff)
          !!! Unknown header type 7f
  00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
  ...
  f0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

To fix the issue, prefetchable limit upper 32 bits register needs to be
cleared firstly. This also adheres to the implementation of
pci_setup_bridge_mmio_pref(). Please see the function for detail.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=216644
Fixes: 6aab5622296b ("PCI: vmd: Clean up domain before enumeration")
Cc: Nirmal Patel <nirmal.patel@linux.intel.com>
Signed-off-by: Adrian Huang <ahuang12@lenovo.com>
---
 drivers/pci/controller/vmd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
index 769eedeb8802..e520aec55b68 100644
--- a/drivers/pci/controller/vmd.c
+++ b/drivers/pci/controller/vmd.c
@@ -526,6 +526,9 @@ static void vmd_domain_reset(struct vmd_dev *vmd)
 				     PCI_CLASS_BRIDGE_PCI))
 					continue;
 
+				/* Clear the upper 32 bits of PREF limit. */
+				memset_io(base + PCI_PREF_LIMIT_UPPER32, 0, 4);
+
 				memset_io(base + PCI_IO_BASE, 0,
 					  PCI_ROM_ADDRESS1 - PCI_IO_BASE);
 			}
-- 
2.31.1