Blame SOURCES/edk2-OvmfPkg-raise-the-PCIEXBAR-base-to-2816-MB-on-Q35.patch

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From d362291ada9ee22316e3c069dc788c4c801b0796 Mon Sep 17 00:00:00 2001
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From: Laszlo Ersek <lersek@redhat.com>
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Date: Tue, 4 Jun 2019 11:06:44 +0200
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Subject: [PATCH 2/3] OvmfPkg: raise the PCIEXBAR base to 2816 MB on Q35
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Message-id: <20190604090645.2847-3-lersek@redhat.com>
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Patchwork-id: 88481
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O-Subject:  [RHEL-8.1.0 edk2 PATCH v2 2/3] OvmfPkg: raise the PCIEXBAR base to
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	2816 MB on Q35
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Bugzilla: 1666941
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Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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Acked-by: Vitaly Kuznetsov <vkuznets@redhat.com>
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(This is a replacement for commit 75136b29541b, "OvmfPkg/PlatformPei:
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reorder the 32-bit PCI window vs. the PCIEXBAR on q35", 2019-05-16).
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Commit 7b8fe63561b4 ("OvmfPkg: PlatformPei: enable PCIEXBAR (aka MMCONFIG
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/ ECAM) on Q35", 2016-03-10) claimed that,
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  On Q35 machine types that QEMU intends to support in the long term, QEMU
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  never lets the RAM below 4 GB exceed 2 GB.
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Alas, this statement came from a misunderstanding that occurred while we
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worked out the interface contract. In fact QEMU does allow the 32-bit RAM
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extend up to 0xB000_0000 (exclusive), in case the RAM size falls in the
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range (0x8000_0000, 0xB000_0000) (i.e., the RAM size is greater than
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2048MB and smaller than 2816MB).
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In turn, such a RAM size (justifiedly) triggers
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  ASSERT (TopOfLowRam <= PciExBarBase);
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in MemMapInitialization(), because we placed the 256MB PCIEXBAR at
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0x8000_0000 (2GB) exactly, relying on the interface contract. (And, the
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32-bit PCI window would follow the PCIEXBAR, covering the [0x9000_0000,
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0xFC00_0000) range.)
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In order to fix this, place the PCIEXBAR at 2816MB (0xB000_0000), and
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start the 32-bit PCI window at 3 GB (0xC000_0000). This shrinks the 32-bit
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PCI window to
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  0xFC00_0000 - 0xC000_0000 = 0x3C00_0000 = 960 MB.
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Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
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Cc: Gerd Hoffmann <kraxel@redhat.com>
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Cc: Jordan Justen <jordan.l.justen@intel.com>
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Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1859
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Signed-off-by: Laszlo Ersek <lersek@redhat.com>
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Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
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Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
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(cherry picked from commit b07de0974b65a6a393c2d477427d1d6c7acce002)
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Signed-off-by: Laszlo Ersek <lersek@redhat.com>
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---
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 OvmfPkg/OvmfPkgIa32.dsc    | 4 ++--
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 OvmfPkg/OvmfPkgIa32X64.dsc | 4 ++--
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 OvmfPkg/OvmfPkgX64.dsc     | 4 ++--
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 3 files changed, 6 insertions(+), 6 deletions(-)
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diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
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index bbf5e38..cf5f2ea 100644
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--- a/OvmfPkg/OvmfPkgIa32.dsc
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+++ b/OvmfPkg/OvmfPkgIa32.dsc
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@@ -497,8 +497,8 @@
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   # the PCIEXBAR register.
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   #
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   # On Q35 machine types that QEMU intends to support in the long term, QEMU
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-  # never lets the RAM below 4 GB exceed 2 GB.
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-  gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress|0x80000000
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+  # never lets the RAM below 4 GB exceed 2816 MB.
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+  gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress|0xB0000000
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 !ifdef $(SOURCE_DEBUG_ENABLE)
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   gEfiSourceLevelDebugPkgTokenSpaceGuid.PcdDebugLoadImageMethod|0x2
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diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
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index 3ec1b91..5a24065 100644
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--- a/OvmfPkg/OvmfPkgIa32X64.dsc
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+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
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@@ -502,8 +502,8 @@
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   # the PCIEXBAR register.
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   #
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   # On Q35 machine types that QEMU intends to support in the long term, QEMU
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-  # never lets the RAM below 4 GB exceed 2 GB.
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-  gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress|0x80000000
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+  # never lets the RAM below 4 GB exceed 2816 MB.
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+  gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress|0xB0000000
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 !ifdef $(SOURCE_DEBUG_ENABLE)
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   gEfiSourceLevelDebugPkgTokenSpaceGuid.PcdDebugLoadImageMethod|0x2
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diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
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index ea54b4b..6ab50c9 100644
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--- a/OvmfPkg/OvmfPkgX64.dsc
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+++ b/OvmfPkg/OvmfPkgX64.dsc
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@@ -502,8 +502,8 @@
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   # the PCIEXBAR register.
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   #
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   # On Q35 machine types that QEMU intends to support in the long term, QEMU
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-  # never lets the RAM below 4 GB exceed 2 GB.
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-  gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress|0x80000000
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+  # never lets the RAM below 4 GB exceed 2816 MB.
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+  gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress|0xB0000000
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 !ifdef $(SOURCE_DEBUG_ENABLE)
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   gEfiSourceLevelDebugPkgTokenSpaceGuid.PcdDebugLoadImageMethod|0x2
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-- 
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1.8.3.1
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