1. Aug 22, 2023
    • Nirmal Patel's avatar
      PCI: vmd: Disable bridge window for domain reset · f73eedc9
      Nirmal Patel authored
      During domain reset process vmd_domain_reset() clears PCI
      configuration space of VMD root ports. But certain platform
      has observed following errors and failed to boot.
        ...
        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 seems to be enabling prefetchable memory if the device disabled
      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
        ...
      
      So, prefetchable memory is ffffffff00000000-575000fffff, which is
      disabled. When memset_io() clears prefetchable base 32 bits register,
      the prefetchable memory becomes 0000000000000000-575000fffff, which is
      enabled and incorrect.
      
      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.
      
      This is believed to be the reason for the failure and in addition the
      sequence of operation in vmd_domain_reset() is not following the PCIe
      specs.
      
      Disable the bridge window by executing a sequence of operations
      borrowed from pci_disable_bridge_window() and pci_setup_bridge_io(),
      that comply with the PCI specifications.
      
      Link: https://lore.kernel.org/r/20230810215029.1177379-1-nirmal.patel@linux.intel.com
      
      
      Signed-off-by: default avatarNirmal Patel <nirmal.patel@linux.intel.com>
      Signed-off-by: default avatarLorenzo Pieralisi <lpieralisi@kernel.org>
      f73eedc9
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