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SubjectRe: [PATCH Part1 RFC v4 13/36] x86/kernel: Make the bss.decrypted section shared in RMP table
On Wed, Jul 07, 2021 at 01:14:43PM -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(+)

Please apply this cleanup before this one.

Thx.

---
From: Borislav Petkov <bp@suse.de>
Subject: [PATCH] x86/head64: Carve out the guest encryption postprocessing into a helper

Carve it out so that it is abstracted out of the main boot path. All
other encrypted guest-relevant processing should be placed in there.

No functional changes.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/head64.c | 55 ++++++++++++++++++++++------------------
1 file changed, 31 insertions(+), 24 deletions(-)

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index de01903c3735..eee24b427237 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -126,6 +126,36 @@ static bool __head check_la57_support(unsigned long physaddr)
}
#endif

+static unsigned long sme_postprocess_startup(struct boot_params *bp, pmdval_t *pmd)
+{
+ unsigned long vaddr, vaddr_end;
+ int i;
+
+ /* Encrypt the kernel and related (if SME is active) */
+ sme_encrypt_kernel(bp);
+
+ /*
+ * Clear the memory encryption mask from the .bss..decrypted section.
+ * The bss section will be memset to zero later in the initialization so
+ * there is no need to zero it after changing the memory encryption
+ * attribute.
+ */
+ if (mem_encrypt_active()) {
+ vaddr = (unsigned long)__start_bss_decrypted;
+ vaddr_end = (unsigned long)__end_bss_decrypted;
+ for (; vaddr < vaddr_end; vaddr += PMD_SIZE) {
+ i = pmd_index(vaddr);
+ pmd[i] -= sme_get_me_mask();
+ }
+ }
+
+ /*
+ * Return the SME encryption mask (if SME is active) to be used as a
+ * modifier for the initial pgdir entry programmed into CR3.
+ */
+ return sme_get_me_mask();
+}
+
/* Code in __startup_64() can be relocated during execution, but the compiler
* doesn't have to generate PC-relative relocations when accessing globals from
* that function. Clang actually does not generate them, which leads to
@@ -135,7 +165,6 @@ static bool __head check_la57_support(unsigned long physaddr)
unsigned long __head __startup_64(unsigned long physaddr,
struct boot_params *bp)
{
- unsigned long vaddr, vaddr_end;
unsigned long load_delta, *p;
unsigned long pgtable_flags;
pgdval_t *pgd;
@@ -276,29 +305,7 @@ unsigned long __head __startup_64(unsigned long physaddr,
*/
*fixup_long(&phys_base, physaddr) += load_delta - sme_get_me_mask();

- /* Encrypt the kernel and related (if SME is active) */
- sme_encrypt_kernel(bp);
-
- /*
- * Clear the memory encryption mask from the .bss..decrypted section.
- * The bss section will be memset to zero later in the initialization so
- * there is no need to zero it after changing the memory encryption
- * attribute.
- */
- if (mem_encrypt_active()) {
- vaddr = (unsigned long)__start_bss_decrypted;
- vaddr_end = (unsigned long)__end_bss_decrypted;
- for (; vaddr < vaddr_end; vaddr += PMD_SIZE) {
- i = pmd_index(vaddr);
- pmd[i] -= sme_get_me_mask();
- }
- }
-
- /*
- * Return the SME encryption mask (if SME is active) to be used as a
- * modifier for the initial pgdir entry programmed into CR3.
- */
- return sme_get_me_mask();
+ return sme_postprocess_startup(bp, pmd);
}

unsigned long __startup_secondary_64(void)
--
2.29.2
--
Regards/Gruss,
Boris.

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

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