Re: [PATCH v2 1/4] OvmfPkg/PlatformInitLib: Add PlatformScanE820 and GetFirstNonAddressCB

["Laszlo Ersek" <lersek@redhat.com>]

On 1/10/23 09:21, Gerd Hoffmann wrote:
> First step replacing the PlatformScanOrAdd64BitE820Ram() function.
> 
> Add a PlatformScanE820() function which loops over the e280 entries
> from FwCfg and calls a callback for each of them.
> 
> Add a GetFirstNonAddressCB() function which will store the first free
> address (right after the last RAM block) in
> PlatformInfoHob->FirstNonAddress.  This replaces calls to
> PlatformScanOrAdd64BitE820Ram() with non-NULL MaxAddress.
> 
> Also drop local FirstNonAddress variables and use
> PlatformInfoHob->FirstNonAddress instead everywhere.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  OvmfPkg/Library/PlatformInitLib/MemDetect.c | 114 ++++++++++++++++----
>  1 file changed, 91 insertions(+), 23 deletions(-)
> 
> diff --git a/OvmfPkg/Library/PlatformInitLib/MemDetect.c b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
> index 0c4956852689..a2a4dc043f2e 100644
> --- a/OvmfPkg/Library/PlatformInitLib/MemDetect.c
> +++ b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
> @@ -251,6 +251,83 @@ PlatformScanOrAdd64BitE820Ram (
>    return EFI_SUCCESS;
>  }
>  
> +typedef VOID (*E820_SCAN_CALLBACK) (
> +  EFI_E820_ENTRY64       *E820Entry,
> +  EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
> +  );
> +
> +/**
> +  Store first address not used by e820 RAM entries in
> +  PlatformInfoHob->FirstNonAddress
> +**/
> +VOID
> +PlatformGetFirstNonAddressCB (
> +  IN     EFI_E820_ENTRY64       *E820Entry,
> +  IN OUT EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
> +  )
> +{
> +  UINT64  Candidate;
> +
> +  if (E820Entry->Type != EfiAcpiAddressRangeMemory) {
> +    return;
> +  }
> +
> +  Candidate = E820Entry->BaseAddr + E820Entry->Length;
> +  if (PlatformInfoHob->FirstNonAddress < Candidate) {
> +    DEBUG ((DEBUG_INFO, "%a: FirstNonAddress=0x%Lx\n", __FUNCTION__, Candidate));
> +    PlatformInfoHob->FirstNonAddress = Candidate;
> +  }
> +}
> +
> +/**
> +  Iterate over the RAM entries in QEMU's fw_cfg E820 RAM map, call the
> +  passed callback for each entry.
> +
> +  @param[in] Callback              The callback function to be called.
> +
> +  @param[in out]  PlatformInfoHob  PlatformInfo struct which is passed
> +                                   through to the callback.
> +
> +  @retval EFI_SUCCESS              The fw_cfg E820 RAM map was found and processed.
> +
> +  @retval EFI_PROTOCOL_ERROR       The RAM map was found, but its size wasn't a
> +                                   whole multiple of sizeof(EFI_E820_ENTRY64). No
> +                                   RAM entry was processed.
> +
> +  @return                          Error codes from QemuFwCfgFindFile(). No RAM
> +                                   entry was processed.
> +**/

(1) I suggest removing the "RAM" references from the above, now that the
type checking is being moved to the callbacks. I think we can just say
"entries" and "entry", without "RAM". Not a huge deal though.

> +STATIC
> +EFI_STATUS
> +PlatformScanE820 (
> +  IN      E820_SCAN_CALLBACK     Callback,
> +  IN OUT  EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
> +  )
> +{
> +  EFI_STATUS            Status;
> +  FIRMWARE_CONFIG_ITEM  FwCfgItem;
> +  UINTN                 FwCfgSize;
> +  EFI_E820_ENTRY64      E820Entry;
> +  UINTN                 Processed;
> +
> +  Status = QemuFwCfgFindFile ("etc/e820", &FwCfgItem, &FwCfgSize);
> +  if (EFI_ERROR (Status)) {
> +    return Status;
> +  }
> +
> +  if (FwCfgSize % sizeof E820Entry != 0) {
> +    return EFI_PROTOCOL_ERROR;
> +  }
> +
> +  QemuFwCfgSelectItem (FwCfgItem);
> +  for (Processed = 0; Processed < FwCfgSize; Processed += sizeof E820Entry) {
> +    QemuFwCfgReadBytes (sizeof E820Entry, &E820Entry);
> +    Callback (&E820Entry, PlatformInfoHob);
> +  }
> +
> +  return EFI_SUCCESS;
> +}
> +
>  /**
>    Returns PVH memmap
>  
> @@ -384,23 +461,17 @@ PlatformGetSystemMemorySizeAbove4gb (
>    Return the highest address that DXE could possibly use, plus one.
>  **/
>  STATIC
> -UINT64
> +VOID
>  PlatformGetFirstNonAddress (
>    IN OUT  EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
>    )
>  {
> -  UINT64                FirstNonAddress;
>    UINT32                FwCfgPciMmio64Mb;
>    EFI_STATUS            Status;
>    FIRMWARE_CONFIG_ITEM  FwCfgItem;
>    UINTN                 FwCfgSize;
>    UINT64                HotPlugMemoryEnd;
>  
> -  //
> -  // set FirstNonAddress to suppress incorrect compiler/analyzer warnings
> -  //
> -  FirstNonAddress = 0;
> -
>    //
>    // If QEMU presents an E820 map, then get the highest exclusive >=4GB RAM
>    // address from it. This can express an address >= 4GB+1TB.
> @@ -408,9 +479,9 @@ PlatformGetFirstNonAddress (
>    // Otherwise, get the flat size of the memory above 4GB from the CMOS (which
>    // can only express a size smaller than 1TB), and add it to 4GB.
>    //
> -  Status = PlatformScanOrAdd64BitE820Ram (FALSE, NULL, &FirstNonAddress);
> +  Status = PlatformScanE820 (PlatformGetFirstNonAddressCB, PlatformInfoHob);

(2) There is one omission in this patch. Namely, we're performing a
conditional maximum search, and because it is conditional, it is
possible that we find zero candidates. In that case, we still need to
have "PlatformInfoHob->FirstNonAddress" set to a sane value.

The original code handles this by initializing FirstNonAddress to 4GB:

  if (MaxAddress != NULL) {
    *MaxAddress = BASE_4GB;
  }

Which is consistent with the comments that *remain* in the code now.

So my request is that, right before this call to PlatformScanE820(),
please set

  PlatformInfoHob->FirstNonAddress = BASE_4GB;

With (2) updated, and (1) updated or not:

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks,
Laszlo


>    if (EFI_ERROR (Status)) {
> -    FirstNonAddress = BASE_4GB + PlatformGetSystemMemorySizeAbove4gb ();
> +    PlatformInfoHob->FirstNonAddress = BASE_4GB + PlatformGetSystemMemorySizeAbove4gb ();
>    }
>  
>    //
> @@ -420,7 +491,7 @@ PlatformGetFirstNonAddress (
>    //
>   #ifdef MDE_CPU_IA32
>    if (!FeaturePcdGet (PcdDxeIplSwitchToLongMode)) {
> -    return FirstNonAddress;
> +    return;
>    }
>  
>   #endif
> @@ -473,7 +544,7 @@ PlatformGetFirstNonAddress (
>      // determines the highest address plus one. The memory hotplug area (see
>      // below) plays no role for the firmware in this case.
>      //
> -    return FirstNonAddress;
> +    return;
>    }
>  
>    //
> @@ -497,15 +568,15 @@ PlatformGetFirstNonAddress (
>        HotPlugMemoryEnd
>        ));
>  
> -    ASSERT (HotPlugMemoryEnd >= FirstNonAddress);
> -    FirstNonAddress = HotPlugMemoryEnd;
> +    ASSERT (HotPlugMemoryEnd >= PlatformInfoHob->FirstNonAddress);
> +    PlatformInfoHob->FirstNonAddress = HotPlugMemoryEnd;
>    }
>  
>    //
>    // SeaBIOS aligns both boundaries of the 64-bit PCI host aperture to 1GB, so
>    // that the host can map it with 1GB hugepages. Follow suit.
>    //
> -  PlatformInfoHob->PcdPciMmio64Base = ALIGN_VALUE (FirstNonAddress, (UINT64)SIZE_1GB);
> +  PlatformInfoHob->PcdPciMmio64Base = ALIGN_VALUE (PlatformInfoHob->FirstNonAddress, (UINT64)SIZE_1GB);
>    PlatformInfoHob->PcdPciMmio64Size = ALIGN_VALUE (PlatformInfoHob->PcdPciMmio64Size, (UINT64)SIZE_1GB);
>  
>    //
> @@ -519,8 +590,8 @@ PlatformGetFirstNonAddress (
>    //
>    // The useful address space ends with the 64-bit PCI host aperture.
>    //
> -  FirstNonAddress = PlatformInfoHob->PcdPciMmio64Base + PlatformInfoHob->PcdPciMmio64Size;
> -  return FirstNonAddress;
> +  PlatformInfoHob->FirstNonAddress = PlatformInfoHob->PcdPciMmio64Base + PlatformInfoHob->PcdPciMmio64Size;
> +  return;
>  }
>  
>  /*
> @@ -781,7 +852,6 @@ PlatformAddressWidthInitialization (
>    IN OUT EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
>    )
>  {
> -  UINT64      FirstNonAddress;
>    UINT8       PhysMemAddressWidth;
>    EFI_STATUS  Status;
>  
> @@ -794,7 +864,7 @@ PlatformAddressWidthInitialization (
>    // First scan host-provided hardware information to assess if the address
>    // space is already known. If so, guest must use those values.
>    //
> -  Status = PlatformScanHostProvided64BitPciMmioEnd (&FirstNonAddress);
> +  Status = PlatformScanHostProvided64BitPciMmioEnd (&PlatformInfoHob->FirstNonAddress);
>  
>    if (EFI_ERROR (Status)) {
>      //
> @@ -806,13 +876,12 @@ PlatformAddressWidthInitialization (
>      // 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);
> +    PlatformGetFirstNonAddress (PlatformInfoHob);
>    }
>  
>    PlatformAddressWidthFromCpuid (PlatformInfoHob, TRUE);
>    if (PlatformInfoHob->PhysMemAddressWidth != 0) {
>      // physical address width is known
> -    PlatformInfoHob->FirstNonAddress = FirstNonAddress;
>      PlatformDynamicMmioWindow (PlatformInfoHob);
>      return;
>    }
> @@ -823,13 +892,13 @@ PlatformAddressWidthInitialization (
>    //   -> try be conservstibe to stay below the guaranteed minimum of
>    //      36 phys bits (aka 64 GB).
>    //
> -  PhysMemAddressWidth = (UINT8)HighBitSet64 (FirstNonAddress);
> +  PhysMemAddressWidth = (UINT8)HighBitSet64 (PlatformInfoHob->FirstNonAddress);
>  
>    //
>    // If FirstNonAddress is not an integral power of two, then we need an
>    // additional bit.
>    //
> -  if ((FirstNonAddress & (FirstNonAddress - 1)) != 0) {
> +  if ((PlatformInfoHob->FirstNonAddress & (PlatformInfoHob->FirstNonAddress - 1)) != 0) {
>      ++PhysMemAddressWidth;
>    }
>  
> @@ -857,7 +926,6 @@ PlatformAddressWidthInitialization (
>    ASSERT (PhysMemAddressWidth <= 48);
>   #endif
>  
> -  PlatformInfoHob->FirstNonAddress     = FirstNonAddress;
>    PlatformInfoHob->PhysMemAddressWidth = PhysMemAddressWidth;
>  }
>