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    SubjectRe: [PATCH Part1 RFC v3 12/22] x86/kernel: Make the bss.decrypted section shared in RMP table
    On Wed, Jun 02, 2021 at 09:04:06AM -0500, Brijesh Singh wrote:
    > The encryption attribute for the bss.decrypted region is cleared in the
    > initial page table build. This is because the section contains the data
    > that need to be shared between the guest and the hypervisor.
    >
    > When SEV-SNP is active, just clearing the encryption attribute in the
    > page table is not enough. The page state need to be updated in the RMP
    > table.
    >
    > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
    > ---
    > arch/x86/kernel/head64.c | 7 +++++++
    > 1 file changed, 7 insertions(+)
    >
    > diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
    > index de01903c3735..f4c3e632345a 100644
    > --- a/arch/x86/kernel/head64.c
    > +++ b/arch/x86/kernel/head64.c
    > @@ -288,7 +288,14 @@ unsigned long __head __startup_64(unsigned long physaddr,
    > if (mem_encrypt_active()) {
    > vaddr = (unsigned long)__start_bss_decrypted;
    > vaddr_end = (unsigned long)__end_bss_decrypted;
    > +
    > for (; vaddr < vaddr_end; vaddr += PMD_SIZE) {
    > + /*
    > + * When SEV-SNP is active then transition the page to shared in the RMP
    > + * table so that it is consistent with the page table attribute change.
    > + */
    > + early_snp_set_memory_shared(__pa(vaddr), __pa(vaddr), PTRS_PER_PMD);
    > +
    > i = pmd_index(vaddr);
    > pmd[i] -= sme_get_me_mask();
    > }
    > --

    It seems to me that all that code from the sme_encrypt_kernel(bp); call
    to the end of the function should be in a separate function in sev.c
    called sev_prepare_kernel(...args...) to be at least abstracted away
    from the main boot path.

    Thx.

    --
    Regards/Gruss,
    Boris.

    https://people.kernel.org/tglx/notes-about-netiquette

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