[PATCH v6 4/5] Ovmf/PlatformPei: Use host-provided GPA end if available

["Ojeda Leon, Nicolas" <ncoleon@amazon.com>]

Read the "hardware-info" item from fw-cfg to extract specifications
of PCI host bridges and analyze the 64-bit apertures of them to
find out the highest 64-bit MMIO address required which determines
the address space required by the guest, and, consequently, the
FirstNonAddress used to calculate size of physical addresses.

Using the static PeiHardwareInfoLib, read the fw-cfg file of
hardware information to extract, one by one, all the host
bridges. Find the last 64-bit MMIO address of each host bridge,
using the HardwareInfoPciHostBridgeLib API, and compare it to an
accumulate value to discover the highest address used, which
corresponds to the highest value that must be included in the
guest's physical address space.

Given that platforms with multiple host bridges may provide the PCI
apertures' addresses, the memory detection logic must take into
account that, if the host provided the MMIO windows that can and must
be used, the guest needs to take those values. Therefore, if the
MMIO windows are found in the host-provided fw-cfg file, skip all the
logic calculating the physical address size and just use the value
provided. Since each PCI host bridge corresponds to an element in
the information provided by the host, each of these must be analyzed
looking for the highest address used.

Cc: Alexander Graf <graf@amazon.de>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Nicolas Ojeda Leon <ncoleon@amazon.com>
---
Notes:
  v6:
  Preparation for merge:

  v5:
  - Moved all changes from MemDetect.c into recently created
    PlatformInitLib/MemDetect.c effectively re-basing this patch
    onto latest master
  - Adapted function name to use Platform____ convention without
    any changes in the logic



---
 OvmfPkg/Library/PlatformInitLib/MemDetect.c   | 148 +++++++++++++++++-
 .../PlatformInitLib/PlatformInitLib.inf       |   1 +
 2 files changed, 142 insertions(+), 7 deletions(-)

diff --git a/OvmfPkg/Library/PlatformInitLib/MemDetect.c b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
index c28d7601f8..942eaf89cf 100644
--- a/OvmfPkg/Library/PlatformInitLib/MemDetect.c
+++ b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
@@ -27,6 +27,7 @@ Module Name:
 #include <Library/BaseLib.h>
 #include <Library/BaseMemoryLib.h>
 #include <Library/DebugLib.h>
+#include <Library/HardwareInfoLib.h>
 #include <Library/HobLib.h>
 #include <Library/IoLib.h>
 #include <Library/MemEncryptSevLib.h>
@@ -527,6 +528,126 @@ PlatformAddressWidthFromCpuid (
     ));
 }
 
+/**
+  Iterate over the PCI host bridges resources information optionally provided
+  in fw-cfg and find the highest address contained in the PCI MMIO windows. If
+  the information is found, return the exclusive end; one past the last usable
+  address.
+
+  @param[out] PciMmioAddressEnd Pointer to one-after End Address updated with
+                                information extracted from host-provided data
+                                or zero if no information available or an
+                                error happened
+
+  @retval EFI_SUCCESS               PCI information was read and the output
+                                    parameter updated with the last valid
+                                    address in the 64-bit MMIO range.
+  @retval EFI_INVALID_PARAMETER     Pointer parameter is invalid
+  @retval EFI_INCOMPATIBLE_VERSION  Hardware information found in fw-cfg
+                                    has an incompatible format
+  @retval EFI_UNSUPPORTED           Fw-cfg is not supported, thus host
+                                    provided information, if any, cannot be
+                                    read
+  @retval EFI_NOT_FOUND             No PCI host bridge information provided
+                                    by the host.
+**/
+STATIC
+EFI_STATUS
+PlatformScanHostProvided64BitPciMmioEnd (
+  OUT UINT64  *PciMmioAddressEnd
+  )
+{
+  EFI_STATUS            Status;
+  HOST_BRIDGE_INFO      HostBridge;
+  FIRMWARE_CONFIG_ITEM  FwCfgItem;
+  UINTN                 FwCfgSize;
+  UINTN                 FwCfgReadIndex;
+  UINTN                 ReadDataSize;
+  UINT64                Above4GMmioEnd;
+
+  if (PciMmioAddressEnd == NULL) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  *PciMmioAddressEnd = 0;
+  Above4GMmioEnd     = 0;
+
+  Status = QemuFwCfgFindFile ("etc/hardware-info", &FwCfgItem, &FwCfgSize);
+  if (EFI_ERROR (Status)) {
+    return Status;
+  }
+
+  QemuFwCfgSelectItem (FwCfgItem);
+
+  FwCfgReadIndex = 0;
+  while (FwCfgReadIndex < FwCfgSize) {
+    Status = QemuFwCfgReadNextHardwareInfoByType (
+               HardwareInfoTypeHostBridge,
+               sizeof (HostBridge),
+               FwCfgSize,
+               &HostBridge,
+               &ReadDataSize,
+               &FwCfgReadIndex
+               );
+
+    if (Status != EFI_SUCCESS) {
+      //
+      // No more data available to read in the file, break
+      // loop and finish process
+      //
+      break;
+    }
+
+    Status = HardwareInfoPciHostBridgeLastMmioAddress (
+               &HostBridge,
+               ReadDataSize,
+               TRUE,
+               &Above4GMmioEnd
+               );
+
+    if (Status != EFI_SUCCESS) {
+      //
+      // Error parsing MMIO apertures and extracting last MMIO
+      // address, reset PciMmioAddressEnd as if no information was
+      // found, to avoid moving forward with incomplete data, and
+      // bail out
+      //
+      DEBUG ((
+        DEBUG_ERROR,
+        "%a: ignoring malformed hardware information from fw_cfg\n",
+        __FUNCTION__
+        ));
+      *PciMmioAddressEnd = 0;
+      return Status;
+    }
+
+    if (Above4GMmioEnd > *PciMmioAddressEnd) {
+      *PciMmioAddressEnd = Above4GMmioEnd;
+    }
+  }
+
+  if (*PciMmioAddressEnd > 0) {
+    //
+    // Host-provided PCI information was found and a MMIO window end
+    // derived from it.
+    // Increase the End address by one to have the output pointing to
+    // one after the address in use (exclusive end).
+    //
+    *PciMmioAddressEnd += 1;
+
+    DEBUG ((
+      DEBUG_INFO,
+      "%a: Pci64End=0x%Lx\n",
+      __FUNCTION__,
+      *PciMmioAddressEnd
+      ));
+
+    return EFI_SUCCESS;
+  }
+
+  return EFI_NOT_FOUND;
+}
+
 /**
   Initialize the PhysMemAddressWidth field in PlatformInfoHob based on guest RAM size.
 **/
@@ -536,8 +657,9 @@ PlatformAddressWidthInitialization (
   IN OUT EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
   )
 {
-  UINT64  FirstNonAddress;
-  UINT8   PhysMemAddressWidth;
+  UINT64      FirstNonAddress;
+  UINT8       PhysMemAddressWidth;
+  EFI_STATUS  Status;
 
   if (PlatformInfoHob->HostBridgeDevId == 0xffff /* microvm */) {
     PlatformAddressWidthFromCpuid (PlatformInfoHob);
@@ -545,12 +667,24 @@ PlatformAddressWidthInitialization (
   }
 
   //
-  // As guest-physical memory size grows, the permanent PEI RAM requirements
-  // are dominated by the identity-mapping page tables built by the DXE IPL.
-  // The DXL IPL keys off of the physical address bits advertized in the CPU
-  // HOB. To conserve memory, we calculate the minimum address width here.
+  // First scan host-provided hardware information to assess if the address
+  // space is already known. If so, guest must use those values.
   //
-  FirstNonAddress     = PlatformGetFirstNonAddress (PlatformInfoHob);
+  Status = PlatformScanHostProvided64BitPciMmioEnd (&FirstNonAddress);
+
+  if (EFI_ERROR (Status)) {
+    //
+    // If the host did not provide valid hardware information leading to a
+    // hard-defined 64-bit MMIO end, fold back to calculating the minimum range
+    // needed.
+    // As guest-physical memory size grows, the permanent PEI RAM requirements
+    // are dominated by the identity-mapping page tables built by the DXE IPL.
+    // The DXL IPL keys off of the physical address bits advertized in the CPU
+    // HOB. To conserve memory, we calculate the minimum address width here.
+    //
+    FirstNonAddress = PlatformGetFirstNonAddress (PlatformInfoHob);
+  }
+
   PhysMemAddressWidth = (UINT8)HighBitSet64 (FirstNonAddress);
 
   //
diff --git a/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf b/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf
index d2a0bec434..d2fa2d998d 100644
--- a/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf
+++ b/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf
@@ -50,6 +50,7 @@
   MtrrLib
   PcdLib
   PciLib
+  PeiHardwareInfoLib
 
 [LibraryClasses.X64]
   TdxLib
-- 
2.17.1




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