[PATCH v8 13/40] x86/kernel: Make the bss.decrypted section shared in RMP table

Brijesh Singh
2021-12-10T15:44:37Z

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);
+
i = pmd_index(vaddr);
pmd[i] -= sme_get_me_mask();
}
--
2.25.1