[PATCH v7 18/45] x86/kernel: Make the bss.decrypted section shared in RMP table

Brijesh Singh
2021-11-10T22:08:35Z

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 968105cec364..ca8536404ed3 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