x86/boot/sev: Support memory acceptance in the EFI stub under SVSM

Commit:

  d54d610243a4 ("x86/boot/sev: Avoid shared GHCB page for early memory acceptance")

provided a fix for SEV-SNP memory acceptance from the EFI stub when
running at VMPL #0. However, that fix was insufficient for SVSM SEV-SNP
guests running at VMPL >0, as those rely on a SVSM calling area, which
is a shared buffer whose address is programmed into a SEV-SNP MSR, and
the SEV init code that sets up this calling area executes much later
during the boot.

Given that booting via the EFI stub at VMPL >0 implies that the firmware
has configured this calling area already, reuse it for performing memory
acceptance in the EFI stub.

Fixes: fcd042e86422 ("x86/sev: Perform PVALIDATE using the SVSM when not at VMPL0")
Tested-by: Tom Lendacky <[email protected]>
Co-developed-by: Tom Lendacky <[email protected]>
Signed-off-by: Tom Lendacky <[email protected]>
Signed-off-by: Ard Biesheuvel <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Cc: <[email protected]>
Cc: Dionna Amalie Glaze <[email protected]>
Cc: Kevin Loughlin <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]

0 files changed, 0 insertions, 0 deletions