Definition of PMD_FLAGS_DEC_WP in arch/x86/mm/mem_encrypt_identity.c

[Arvind Sankar]

Hi, I have a question about this definition in
arch/x86/mm/mem_encrypt_identity.c:

        #define PMD_FLAGS_LARGE         (__PAGE_KERNEL_LARGE_EXEC & 
~_PAGE_GLOBAL)

        #define PMD_FLAGS_DEC           PMD_FLAGS_LARGE
        #define PMD_FLAGS_DEC_WP        ((PMD_FLAGS_DEC & ~_PAGE_CACHE_MASK) | \
                                         (_PAGE_PAT | _PAGE_PWT))

_PAGE_CACHE_MASK and _PAGE_PAT are for 4k pages, not 2M pages. The
definition of PMD_FLAGS_DEC_WP clears the PSE bit by masking out
_PAGE_CACHE_MASK, and sets it again by setting _PAGE_PAT, resulting in
PMD_FLAGS_DEC_WP actually being write-through, not write-protected,
using PAT index 1.

Shouldn't the definition be

        #define PMD_FLAGS_DEC_WP        (PMD_FLAGS_DEC | _PAGE_PAT_LARGE | 
_PAGE_PWT)

for write-protected using PAT index 5?

I guess the difference doesn't actually matter for encrypt-in-place? But
mem_encrypt_boot.S takes pains to initialize PA5 to be write-protected,
and it looks like it won't actually be used.

Thanks.