[edk2-devel] [PATCH for-edk2-stable201905 4/6] Revert "OvmfPkg/PlatformPei: assign PciSize on both i440fx/q35 branches explicitly"

[Laszlo Ersek]

This reverts commit 60e95bf5094fbb9b728729ccfaf32184b3662317.

The original fix for <https://bugzilla.tianocore.org/show_bug.cgi?id=1814>
triggered a bug / incorrect assumption in QEMU.

QEMU assumes that the PCIEXBAR is below the 32-bit PCI window, not above
it. When the firmware doesn't satisfy this assumption, QEMU generates an
\_SB.PCI0._CRS object in the ACPI DSDT that does not reflect the
firmware's 32-bit MMIO BAR assignments. This causes OSes to re-assign
32-bit MMIO BARs.

Working around the problem in the firmware looks less problematic than
fixing QEMU. Revert the original changes first, before implementing an
alternative fix.

Cc: Ard Biesheuvel <ard.biesheuvel at linaro.org>
Cc: Gerd Hoffmann <kraxel at redhat.com>
Cc: Jordan Justen <jordan.l.justen at intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1859
Signed-off-by: Laszlo Ersek <lersek at redhat.com>
---
 OvmfPkg/PlatformPei/Platform.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/OvmfPkg/PlatformPei/Platform.c b/OvmfPkg/PlatformPei/Platform.c
index 5e0a15484230..0876316eefbc 100644
--- a/OvmfPkg/PlatformPei/Platform.c
+++ b/OvmfPkg/PlatformPei/Platform.c
@@ -190,10 +190,8 @@ MemMapInitialization (
       ASSERT (TopOfLowRam <= PciExBarBase);
       ASSERT (PciExBarBase <= MAX_UINT32 - SIZE_256MB);
       PciBase = (UINT32)(PciExBarBase + SIZE_256MB);
-      PciSize = 0xFC000000 - PciBase;
     } else {
       PciBase = (TopOfLowRam < BASE_2GB) ? BASE_2GB : TopOfLowRam;
-      PciSize = 0xFC000000 - PciBase;
     }
 
     //
@@ -209,6 +207,7 @@ MemMapInitialization (
     // 0xFED20000    gap                          896 KB
     // 0xFEE00000    LAPIC                          1 MB
     //
+    PciSize = 0xFC000000 - PciBase;
     AddIoMemoryBaseSizeHob (PciBase, PciSize);
     PcdStatus = PcdSet64S (PcdPciMmio32Base, PciBase);
     ASSERT_RETURN_ERROR (PcdStatus);
-- 
2.19.1.3.g30247aa5d201



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