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    SubjectRe: [PATCH v8 13/40] x86/kernel: Make the bss.decrypted section shared in RMP table
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    On 1/4/22 11:56 AM, Venu Busireddy wrote:
    > On 2021-12-10 09:43:05 -0600, 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 fa02402dcb9b..72c5082a3ba4 100644
    >> --- a/arch/x86/kernel/head64.c
    >> +++ b/arch/x86/kernel/head64.c
    >> @@ -143,7 +143,14 @@ static unsigned long sme_postprocess_startup(struct boot_params *bp, pmdval_t *p
    >> if (sme_get_me_mask()) {
    >> 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);
    >
    > Shouldn't the first argument be vaddr as below?
    >

    Nope, sme_postprocess_startup() is called while we are fixing the
    initial page table and running with identity mapping (so va == pa).

    thanks

    > early_snp_set_memory_shared(vaddr, __pa(vaddr), PTRS_PER_PMD);
    >
    > Venu
    >

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