Re: [edk2-devel] [PATCH v2] OvmfPkg: Create additional PML1 entries for large SEV-SNP VMs

["Lendacky, Thomas" <thomas.lendacky@amd.com>]

On 6/2/23 17:49, Ard Biesheuvel wrote:
> On Fri, 2 Jun 2023 at 23:20, Lendacky, Thomas via groups.io
> <thomas.lendacky=amd.com@groups.io> wrote:
>>
>> On 1/26/23 14:26, Mikolaj Lisik wrote:
>>> Edk2 was failing, rather than creating more PML4 entries, when they
>>> weren't present in the initial memory acceptance flow. Because of that
>>> VMs with more than 512G memory were crashing. This code fixes that.
>>>
>>> This change affects only SEV-SNP VMs.
>>>
>>> The code was tested by successfully booting a 512G SEV-SNP VM.
>>>
>>> Signed-off-by: Mikolaj Lisik <lisik@google.com>
>>
>> I don't see where this was merged. Both Gerd and I acked it back in
>> January, was there a problem with it?
>>
> 
> I wasn't cc'ed.

Ah, I hadn't noticed that you weren't cc'd...

> 
> I've queued this up now.

Thanks, Ard!

Tom

> 
> 
> 
>>
>>> ---
>>>    .../X64/PeiDxeVirtualMemory.c                 | 26 ++++++++++++-------
>>>    1 file changed, 17 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c
>>> index b9c0a5b25a..75c2c36bb4 100644
>>> --- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c
>>> +++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c
>>> @@ -548,6 +548,7 @@ InternalMemEncryptSevCreateIdentityMap1G (
>>>      PAGE_MAP_AND_DIRECTORY_POINTER  *PageMapLevel4Entry;
>>>      PAGE_TABLE_1G_ENTRY             *PageDirectory1GEntry;
>>>      UINT64                          PgTableMask;
>>> +  UINT64                          *NewPageTable;
>>>      UINT64                          AddressEncMask;
>>>      BOOLEAN                         IsWpEnabled;
>>>      RETURN_STATUS                   Status;
>>> @@ -602,15 +603,22 @@ InternalMemEncryptSevCreateIdentityMap1G (
>>>        PageMapLevel4Entry  = (VOID *)(Cr3BaseAddress & ~PgTableMask);
>>>        PageMapLevel4Entry += PML4_OFFSET (PhysicalAddress);
>>>        if (!PageMapLevel4Entry->Bits.Present) {
>>> -      DEBUG ((
>>> -        DEBUG_ERROR,
>>> -        "%a:%a: bad PML4 for Physical=0x%Lx\n",
>>> -        gEfiCallerBaseName,
>>> -        __FUNCTION__,
>>> -        PhysicalAddress
>>> -        ));
>>> -      Status = RETURN_NO_MAPPING;
>>> -      goto Done;
>>> +      NewPageTable = AllocatePageTableMemory (1);
>>> +      if (NewPageTable == NULL) {
>>> +        DEBUG ((
>>> +          DEBUG_ERROR,
>>> +          "%a:%a: failed to allocate a new PML4 entry\n",
>>> +          gEfiCallerBaseName,
>>> +          __FUNCTION__
>>> +          ));
>>> +        Status = RETURN_NO_MAPPING;
>>> +        goto Done;
>>> +      }
>>> +      SetMem (NewPageTable, EFI_PAGE_SIZE, 0);
>>> +      PageMapLevel4Entry->Uint64          = (UINT64)(UINTN)NewPageTable | AddressEncMask;
>>> +      PageMapLevel4Entry->Bits.MustBeZero = 0;
>>> +      PageMapLevel4Entry->Bits.ReadWrite  = 1;
>>> +      PageMapLevel4Entry->Bits.Present    = 1;
>>>        }
>>>
>>>        PageDirectory1GEntry = (VOID *)(
>>
>>
>> 
>>
>>