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MdeModulePkg/PciBusDxe: Honor SpecificFlag for PMem64 in UpdatePciInfo

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When UpdatePciInfo() downgrades a PciBarTypePMem64 BAR to a 32-bit type
via EFI_INCOMPATIBLE_PCI_DEVICE_SUPPORT_PROTOCOL, it unconditionally
assigns PciBarTypePMem32 regardless of SpecificFlag, placing the BAR in
the prefetchable bridge window even when the platform intended the
non-prefetchable window.

The ACPI resource descriptor's SpecificFlag field encodes the intended
prefetchability of the constrained resource, using the bit:
EFI_ACPI_MEMORY_RESOURCE_SPECIFIC_FLAG_CACHEABLE_PREFETCHABLE.

Fix this by checking the bit in SpecificFlag to select PciBarTypePMem32 or
PciBarTypeMem32, consistent with DumpPpbPaddingResource() in
PciEnumeratorSupport.c that uses the bit as the sole discriminator
between the two 32-bit BAR types.

Signed-off-by: Phil Noh <Phil.Noh@amd.com>
This commit is contained in:
Phil Noh 2026-06-25 15:41:25 -05:00 • committed by mergify[bot]
parent 3613891d77
commit c70637de12
1 changed files with 9 additions and 2 deletions
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11
MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c
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@ -4,7 +4,7 @@
Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.<BR>
Copyright (c) 2006 - 2021, Intel Corporation. All rights reserved.<BR>
(C) Copyright 2015 Hewlett Packard Enterprise Development LP<BR>
Copyright (C) 2023 Advanced Micro Devices, Inc. All rights reserved.<BR>
Copyright (C) 2023 - 2026 Advanced Micro Devices, Inc. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
@ -1595,7 +1595,14 @@ UpdatePciInfo (
if (PciIoDevice->PciBar[BarIndex].BarType == PciBarTypePMem64) {
switch (Ptr->AddrSpaceGranularity) {
case 32:
PciIoDevice->PciBar[BarIndex].BarType = PciBarTypePMem32;
if ((Ptr->SpecificFlag & EFI_ACPI_MEMORY_RESOURCE_SPECIFIC_FLAG_CACHEABLE_PREFETCHABLE) ==
EFI_ACPI_MEMORY_RESOURCE_SPECIFIC_FLAG_CACHEABLE_PREFETCHABLE)
{
PciIoDevice->PciBar[BarIndex].BarType = PciBarTypePMem32;
} else {
PciIoDevice->PciBar[BarIndex].BarType = PciBarTypeMem32;
}
case 64:
PciIoDevice->PciBar[BarIndex].BarTypeFixed = TRUE;
break;