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

["Ard Biesheuvel" <ardb@kernel.org>]

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.

I've queued this up now.



>
> > ---
> >   .../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 *)(
>
>
> 
>
>