On 11/21/22 6:39 AM, Borislav Petkov wrote:

On Fri, Nov 18, 2022 at 02:55:32AM +0000, Michael Kelley (LINUX) wrote:

quoted

But I had not thought about TDX.  In the TDX case, it appears that
sme_postprocess_startup() will not decrypt the bss_decrypted section.
The corresponding mem_encrypt_free_decrypted_mem() is a no-op unless
CONFIG_AMD_MEM_ENCRYPT is set.  But maybe if someone builds a
kernel image that supports both TDX and AMD encryption, it could break

sme_me_mask better be 0 on a kernel with both built in and running as a
TDX guest.

Yes. It will be 0 in TDX. In sme_enable(), AMD code checks for CPUID
support before updating the sme_me_mask.

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer