[PATCH 3/3] OvmfPkg/PlatformInitLib: simplify mtrr setup


Gerd Hoffmann
 

With the new mmconfig location at 0xe0000000 above the 32-bit PCI MMIO
window we don't have to special-case the mmconfig xbar any more. We'll
just add a mtrr uncachable entry starting at MMIO window base and ending
at 4GB.

Update comments to match reality.

Signed-off-by: Gerd Hoffmann <kraxel@...>
---
OvmfPkg/Library/PlatformInitLib/MemDetect.c | 36 +++++++++------------
1 file changed, 15 insertions(+), 21 deletions(-)

diff --git a/OvmfPkg/Library/PlatformInitLib/MemDetect.c b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
index 5aeeeff89f57..fd5ae42243ba 100644
--- a/OvmfPkg/Library/PlatformInitLib/MemDetect.c
+++ b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
@@ -61,33 +61,20 @@ PlatformQemuUc32BaseInitialization (
return;
}

+ ASSERT (
+ PlatformInfoHob->HostBridgeDevId == INTEL_Q35_MCH_DEVICE_ID ||
+ PlatformInfoHob->HostBridgeDevId == INTEL_82441_DEVICE_ID
+ );
+
PlatformGetSystemMemorySizeBelow4gb (PlatformInfoHob);

if (PlatformInfoHob->HostBridgeDevId == INTEL_Q35_MCH_DEVICE_ID) {
ASSERT (PcdGet64 (PcdPciExpressBaseAddress) <= MAX_UINT32);
ASSERT (PcdGet64 (PcdPciExpressBaseAddress) >= PlatformInfoHob->LowMemory);
-
- if (PlatformInfoHob->LowMemory <= BASE_2GB) {
- // Newer qemu with gigabyte aligned memory,
- // 32-bit pci mmio window is 2G -> 4G then.
- PlatformInfoHob->Uc32Base = BASE_2GB;
- } else {
- //
- // On q35, the 32-bit area that we'll mark as UC, through variable MTRRs,
- // starts at PcdPciExpressBaseAddress. The platform DSC is responsible for
- // setting PcdPciExpressBaseAddress such that describing the
- // [PcdPciExpressBaseAddress, 4GB) range require a very small number of
- // variable MTRRs (preferably 1 or 2).
- //
- PlatformInfoHob->Uc32Base = (UINT32)PcdGet64 (PcdPciExpressBaseAddress);
- }
-
- return;
}

- ASSERT (PlatformInfoHob->HostBridgeDevId == INTEL_82441_DEVICE_ID);
//
- // On i440fx, start with the [LowerMemorySize, 4GB) range. Make sure one
+ // Start with the [LowerMemorySize, 4GB) range. Make sure one
// variable MTRR suffices by truncating the size to a whole power of two,
// while keeping the end affixed to 4GB. This will round the base up.
//
@@ -1027,6 +1014,13 @@ PlatformQemuInitializeRam (
// practically any alignment, and we may not have enough variable MTRRs to
// cover it exactly.
//
+ // Because of that PlatformQemuUc32BaseInitialization() will round
+ // up PlatformInfoHob->LowMemory to make sure a single mtrr register
+ // is enough. The the result will be stored in
+ // PlatformInfoHob->Uc32Base. On a typical qemu configuration with
+ // gigabyte-alignment being used LowMemory will be 2 or 3 GB and no
+ // rounding is needed, so LowMemory and Uc32Base will be identical.
+ //
if (IsMtrrSupported () && (PlatformInfoHob->HostBridgeDevId != CLOUDHV_DEVICE_ID)) {
MtrrGetAllMtrrs (&MtrrSettings);

@@ -1056,8 +1050,8 @@ PlatformQemuInitializeRam (
ASSERT_EFI_ERROR (Status);

//
- // Set the memory range from the start of the 32-bit MMIO area (32-bit PCI
- // MMIO aperture on i440fx, PCIEXBAR on q35) to 4GB as uncacheable.
+ // Set the memory range from the start of the 32-bit PCI MMIO
+ // aperture to 4GB as uncacheable.
//
Status = MtrrSetMemoryAttribute (
PlatformInfoHob->Uc32Base,
--
2.39.1

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