From b07de0974b65a6a393c2d477427d1d6c7acce002 Mon Sep 17 00:00:00 2001 From: Laszlo Ersek Date: Wed, 29 May 2019 11:59:02 +0200 Subject: [PATCH] OvmfPkg: raise the PCIEXBAR base to 2816 MB on Q35 (This is a replacement for commit 75136b29541b, "OvmfPkg/PlatformPei: reorder the 32-bit PCI window vs. the PCIEXBAR on q35", 2019-05-16). Commit 7b8fe63561b4 ("OvmfPkg: PlatformPei: enable PCIEXBAR (aka MMCONFIG / ECAM) on Q35", 2016-03-10) claimed that, On Q35 machine types that QEMU intends to support in the long term, QEMU never lets the RAM below 4 GB exceed 2 GB. Alas, this statement came from a misunderstanding that occurred while we worked out the interface contract. In fact QEMU does allow the 32-bit RAM extend up to 0xB000_0000 (exclusive), in case the RAM size falls in the range (0x8000_0000, 0xB000_0000) (i.e., the RAM size is greater than 2048MB and smaller than 2816MB). In turn, such a RAM size (justifiedly) triggers ASSERT (TopOfLowRam <= PciExBarBase); in MemMapInitialization(), because we placed the 256MB PCIEXBAR at 0x8000_0000 (2GB) exactly, relying on the interface contract. (And, the 32-bit PCI window would follow the PCIEXBAR, covering the [0x9000_0000, 0xFC00_0000) range.) In order to fix this, place the PCIEXBAR at 2816MB (0xB000_0000), and start the 32-bit PCI window at 3 GB (0xC000_0000). This shrinks the 32-bit PCI window to 0xFC00_0000 - 0xC000_0000 = 0x3C00_0000 = 960 MB. Cc: Ard Biesheuvel Cc: Gerd Hoffmann Cc: Jordan Justen Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1859 Signed-off-by: Laszlo Ersek Reviewed-by: Philippe Mathieu-Daude Acked-by: Ard Biesheuvel --- OvmfPkg/OvmfPkgIa32.dsc | 4 ++-- OvmfPkg/OvmfPkgIa32X64.dsc | 4 ++-- OvmfPkg/OvmfPkgX64.dsc | 4 ++-- 3 files changed, 6 insertions(+), 6 deletions(-) diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc index 578fc6c98e..e74a9d5a51 100644 --- a/OvmfPkg/OvmfPkgIa32.dsc +++ b/OvmfPkg/OvmfPkgIa32.dsc @@ -492,8 +492,8 @@ # the PCIEXBAR register. # # On Q35 machine types that QEMU intends to support in the long term, QEMU - # never lets the RAM below 4 GB exceed 2 GB. - gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress|0x80000000 + # never lets the RAM below 4 GB exceed 2816 MB. + gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress|0xB0000000 !ifdef $(SOURCE_DEBUG_ENABLE) gEfiSourceLevelDebugPkgTokenSpaceGuid.PcdDebugLoadImageMethod|0x2 diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc index eade8f62d3..67ac015991 100644 --- a/OvmfPkg/OvmfPkgIa32X64.dsc +++ b/OvmfPkg/OvmfPkgIa32X64.dsc @@ -497,8 +497,8 @@ # the PCIEXBAR register. # # On Q35 machine types that QEMU intends to support in the long term, QEMU - # never lets the RAM below 4 GB exceed 2 GB. - gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress|0x80000000 + # never lets the RAM below 4 GB exceed 2816 MB. + gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress|0xB0000000 !ifdef $(SOURCE_DEBUG_ENABLE) gEfiSourceLevelDebugPkgTokenSpaceGuid.PcdDebugLoadImageMethod|0x2 diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc index 733a4c9d8a..68073ef55b 100644 --- a/OvmfPkg/OvmfPkgX64.dsc +++ b/OvmfPkg/OvmfPkgX64.dsc @@ -497,8 +497,8 @@ # the PCIEXBAR register. # # On Q35 machine types that QEMU intends to support in the long term, QEMU - # never lets the RAM below 4 GB exceed 2 GB. - gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress|0x80000000 + # never lets the RAM below 4 GB exceed 2816 MB. + gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress|0xB0000000 !ifdef $(SOURCE_DEBUG_ENABLE) gEfiSourceLevelDebugPkgTokenSpaceGuid.PcdDebugLoadImageMethod|0x2 -- 2.39.2