Re: [edk2-devel] [PATCH v4 23/35] OvmfPkg/XenPlatformPei: Rework memory detection

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

On 07/29/19 17:39, Anthony PERARD wrote:
> When running as a Xen PVH guest, there is no CMOS to read the memory
> size from.  Rework GetSystemMemorySize(Below|Above)4gb() so they can
> work without CMOS by reading the e820 table.
> 
> Rework XenPublishRamRegions to also care for the reserved and ACPI
> entry in the e820 table. The region that was added by InitializeXen()
> isn't needed as that same entry is in the e820 table provided by
> hvmloader.
> 
> MTRR settings aren't modified anymore, on HVM it's already done by
> hvmloader, on PVH it is supposed to have sane default. MTRR will need
> to be done properly but keeping what's already been done by programmes
> that has runned before OVMF will do for now.

(1) s/programmes that has runned/programs that have run/

> 
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1689
> Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
> Acked-by: Laszlo Ersek <lersek@redhat.com>
> ---
> 
> Notes:
>     v4:
>     - some coding style
>     - Added AddReservedMemoryRangeHob, and using it.
>     - this patch now replace "OvmfPkg/XenPlatformPei: Reserve hvmloader's memory only when it has run"
>       from v3.  hvmloader have added an entry in the e820 table, there is no
>       need for a special case.
>     - now, everything that is in the e820 table is added to OVMF's memory
>       map, no more skipping ACPI entries or hvmloader's reserved entries.
>       Instead, we look for the local APIC region and avoid it if it is
>       present in the e820.
>     - rework commit message
> 
>  OvmfPkg/XenPlatformPei/Platform.h  | 13 ++++++
>  OvmfPkg/XenPlatformPei/MemDetect.c | 69 +++++++++++++++++++++++++++++
>  OvmfPkg/XenPlatformPei/Platform.c  | 11 +++++
>  OvmfPkg/XenPlatformPei/Xen.c       | 70 +++++++++++++++++++-----------
>  4 files changed, 137 insertions(+), 26 deletions(-)
> 
> diff --git a/OvmfPkg/XenPlatformPei/Platform.h b/OvmfPkg/XenPlatformPei/Platform.h
> index db9a62572f..7661f4a8de 100644
> --- a/OvmfPkg/XenPlatformPei/Platform.h
> +++ b/OvmfPkg/XenPlatformPei/Platform.h
> @@ -44,6 +44,13 @@ AddReservedMemoryBaseSizeHob (
>    BOOLEAN                     Cacheable
>    );
>  
> +VOID
> +AddReservedMemoryRangeHob (
> +  EFI_PHYSICAL_ADDRESS        MemoryBase,
> +  EFI_PHYSICAL_ADDRESS        MemoryLimit,
> +  BOOLEAN                     Cacheable
> +  );
> +
>  VOID
>  AddressWidthInitialization (
>    VOID
> @@ -114,6 +121,12 @@ XenPublishRamRegions (
>    VOID
>    );
>  
> +EFI_STATUS
> +XenGetE820Map (
> +  EFI_E820_ENTRY64 **Entries,
> +  UINT32 *Count
> +  );
> +
>  extern EFI_BOOT_MODE mBootMode;
>  
>  extern UINT8 mPhysMemAddressWidth;
> diff --git a/OvmfPkg/XenPlatformPei/MemDetect.c b/OvmfPkg/XenPlatformPei/MemDetect.c
> index cf95f9c474..1f81eee407 100644
> --- a/OvmfPkg/XenPlatformPei/MemDetect.c
> +++ b/OvmfPkg/XenPlatformPei/MemDetect.c
> @@ -96,6 +96,45 @@ Q35TsegMbytesInitialization (
>    mQ35TsegMbytes = ExtendedTsegMbytes;
>  }
>  
> +STATIC
> +UINT64
> +GetHighestSystemMemoryAddress (
> +  BOOLEAN       Below4gb
> +  )
> +{
> +  EFI_E820_ENTRY64    *E820Map;
> +  UINT32              E820EntriesCount;
> +  EFI_E820_ENTRY64    *Entry;
> +  EFI_STATUS          Status;
> +  UINT32              Loop;
> +  UINT64              HighestAddress;
> +  UINT64              EntryEnd;
> +
> +  HighestAddress = 0;
> +
> +  Status = XenGetE820Map (&E820Map, &E820EntriesCount);
> +  ASSERT_EFI_ERROR (Status);
> +
> +  for (Loop = 0; Loop < E820EntriesCount; Loop++) {
> +    Entry = E820Map + Loop;
> +    EntryEnd = Entry->BaseAddr + Entry->Length;
> +
> +    if (Entry->Type == EfiAcpiAddressRangeMemory &&
> +        EntryEnd > HighestAddress) {
> +
> +      if (Below4gb && (EntryEnd <= BASE_4GB)) {
> +        HighestAddress = EntryEnd;
> +      } else if (!Below4gb && (EntryEnd >= BASE_4GB)) {
> +        HighestAddress = EntryEnd;
> +      }
> +    }
> +  }
> +
> +  //
> +  // Round down the end address.
> +  //
> +  return HighestAddress & ~(UINT64)EFI_PAGE_MASK;
> +}
>  
>  UINT32
>  GetSystemMemorySizeBelow4gb (
> @@ -105,6 +144,19 @@ GetSystemMemorySizeBelow4gb (
>    UINT8 Cmos0x34;
>    UINT8 Cmos0x35;
>  
> +  //
> +  // In PVH case, there is no CMOS, we have to calculate the memory size
> +  // from parsing the E820
> +  //
> +  if (XenPvhDetected ()) {
> +    UINT64  HighestAddress;
> +
> +    HighestAddress = GetHighestSystemMemoryAddress (TRUE);
> +    ASSERT (HighestAddress > 0 && HighestAddress <= BASE_4GB);
> +
> +    return HighestAddress;
> +  }
> +
>    //
>    // CMOS 0x34/0x35 specifies the system memory above 16 MB.
>    // * CMOS(0x35) is the high byte
> @@ -129,6 +181,23 @@ GetSystemMemorySizeAbove4gb (
>    UINT32 Size;
>    UINTN  CmosIndex;
>  
> +  //
> +  // In PVH case, there is no CMOS, we have to calculate the memory size
> +  // from parsing the E820
> +  //
> +  if (XenPvhDetected ()) {
> +    UINT64  HighestAddress;
> +
> +    HighestAddress = GetHighestSystemMemoryAddress (FALSE);
> +    ASSERT (HighestAddress == 0 || HighestAddress >= BASE_4GB);
> +
> +    if (HighestAddress >= BASE_4GB) {
> +      HighestAddress -= BASE_4GB;
> +    }
> +
> +    return HighestAddress;
> +  }
> +
>    //
>    // CMOS 0x5b-0x5d specifies the system memory above 4GB MB.
>    // * CMOS(0x5d) is the most significant size byte
> diff --git a/OvmfPkg/XenPlatformPei/Platform.c b/OvmfPkg/XenPlatformPei/Platform.c
> index 6aaafc3ee9..2f42ca6ccd 100644
> --- a/OvmfPkg/XenPlatformPei/Platform.c
> +++ b/OvmfPkg/XenPlatformPei/Platform.c
> @@ -102,6 +102,17 @@ AddReservedMemoryBaseSizeHob (
>      );
>  }
>  
> +VOID
> +AddReservedMemoryRangeHob (
> +  EFI_PHYSICAL_ADDRESS        MemoryBase,
> +  EFI_PHYSICAL_ADDRESS        MemoryLimit,
> +  BOOLEAN                     Cacheable
> +  )
> +{
> +  AddReservedMemoryBaseSizeHob (MemoryBase,
> +    (UINT64)(MemoryLimit - MemoryBase), Cacheable);
> +}
> +
>  VOID
>  AddIoMemoryRangeHob (
>    EFI_PHYSICAL_ADDRESS        MemoryBase,
> diff --git a/OvmfPkg/XenPlatformPei/Xen.c b/OvmfPkg/XenPlatformPei/Xen.c
> index a21d657357..182e96cc5b 100644
> --- a/OvmfPkg/XenPlatformPei/Xen.c
> +++ b/OvmfPkg/XenPlatformPei/Xen.c
> @@ -276,9 +276,12 @@ XenPublishRamRegions (
>    VOID
>    )
>  {
> -  EFI_E820_ENTRY64  *E820Map;
> -  UINT32            E820EntriesCount;
> -  EFI_STATUS        Status;
> +  EFI_E820_ENTRY64      *E820Map;
> +  UINT32                E820EntriesCount;
> +  EFI_STATUS            Status;
> +  EFI_E820_ENTRY64      *Entry;
> +  UINTN                 Index;
> +  EFI_PHYSICAL_ADDRESS  LocalApic;
>  
>    DEBUG ((DEBUG_INFO, "Using memory map provided by Xen\n"));
>  
> @@ -287,26 +290,47 @@ XenPublishRamRegions (
>    //
>    E820EntriesCount = 0;
>    Status = XenGetE820Map (&E820Map, &E820EntriesCount);
> -
>    ASSERT_EFI_ERROR (Status);
>  
> -  if (E820EntriesCount > 0) {
> -    EFI_E820_ENTRY64 *Entry;
> -    UINT32 Loop;
> -
> -    for (Loop = 0; Loop < E820EntriesCount; Loop++) {
> -      Entry = E820Map + Loop;
> -
> -      //
> -      // Only care about RAM
> -      //
> -      if (Entry->Type != EfiAcpiAddressRangeMemory) {
> -        continue;
> +  LocalApic = PcdGet32(PcdCpuLocalApicBaseAddress);

(2) missing space before "(" -- but, actually, please see below


> +  AddIoMemoryBaseSizeHob (LocalApic, SIZE_1MB);
> +
> +  for (Index = 0; Index < E820EntriesCount; Index++) {
> +    UINT64 Base;
> +    UINT64 End;
> +
> +    Entry = &E820Map[Index];
> +
> +    //
> +    // Round up the start address, and round down the end address.
> +    //
> +    Base = ALIGN_VALUE (Entry->BaseAddr, (UINT64)EFI_PAGE_SIZE);
> +    End = (Entry->BaseAddr + Entry->Length) & ~(UINT64)EFI_PAGE_MASK;
> +
> +    switch (Entry->Type) {
> +    case EfiAcpiAddressRangeMemory:
> +      AddMemoryRangeHob (Base, End);
> +      break;
> +    case EfiAcpiAddressRangeACPI:
> +      AddReservedMemoryRangeHob (Base, End, FALSE);
> +      break;
> +    case EfiAcpiAddressRangeReserved:
> +      if (Base < LocalApic && LocalApic < End) {
> +        //
> +        // hvmloader marks a range that overlaps with the local APIC memory
> +        // mapped region as reserved, but CpuDxe wants it as mapped IO. We
> +        // have already added it as mapped IO, so skip it here.
> +        //
> +        AddReservedMemoryRangeHob (Base, LocalApic, FALSE);
> +        if (End > (LocalApic + SIZE_1MB)) {
> +          AddReservedMemoryRangeHob (LocalApic + SIZE_1MB, End, FALSE);
> +        }
> +      } else {
> +        AddReservedMemoryRangeHob (Base, End, FALSE);
>        }

(3) Not sure how general you want to be here, but I don't think this is
fully general. How about:

(3a) before the loop, drop "LocalApic", and add:

  UINT64 LapicBase;
  UINT64 LapicEnd;

  LapicBase = PcdGet32 (PcdCpuLocalApicBaseAddress);
  LapicEnd = LapicBase + SIZE_1MB;

(3b) inside the loop body, near the top of the block, add:

  UINT64 ReservedBase;
  UINT64 ReservedEnd;

(3c) under the EfiAcpiAddressRangeReserved case label:

  //
  // add LAPIC predecessor range, if any
  //
  ReservedBase = Base;
  ReservedEnd = MIN (End, LapicBase);
  if (ReservedBase < ReservedEnd) {
    AddReservedMemoryRangeHob (ReservedBase, ReservedEnd, FALSE);
  }

  //
  // add LAPIC successor range, if any
  //
  ReservedBase = MAX (Base, LapicEnd);
  ReservedEnd = End;
  if (ReservedBase < ReservedEnd) {
    AddReservedMemoryRangeHob (ReservedBase, ReservedEnd, FALSE);
  }

This will cover all possible constellations between the [LapicBase,
LapicEnd) and [Base, End) intervals.

--*--

Regarding the approach itself, I'll defer to Roger.

Thanks
Laszlo

> -
> -      AddMemoryBaseSizeHob (Entry->BaseAddr, Entry->Length);
> -
> -      MtrrSetMemoryAttribute (Entry->BaseAddr, Entry->Length, CacheWriteBack);
> +      break;
> +    default:
> +      break;
>      }
>    }
>  }
> @@ -326,12 +350,6 @@ InitializeXen (
>  {
>    RETURN_STATUS PcdStatus;
>  
> -  //
> -  // Reserve away HVMLOADER reserved memory [0xFC000000,0xFD000000).
> -  // This needs to match HVMLOADER RESERVED_MEMBASE/RESERVED_MEMSIZE.
> -  //
> -  AddReservedMemoryBaseSizeHob (0xFC000000, 0x1000000, FALSE);
> -
>    PcdStatus = PcdSetBoolS (PcdPciDisableBusEnumeration, TRUE);
>    ASSERT_RETURN_ERROR (PcdStatus);
>  
>