Re: [PATCH v3 5/8] x86/sme: Replace occurrences of sme_active() with cc_platform_has()

Kirill A. Shutemov
2021-09-21T21:22:55Z

On Tue, Sep 21, 2021 at 07:47:15PM +0200, Borislav Petkov wrote:
> On Tue, Sep 21, 2021 at 12:04:58PM -0500, Tom Lendacky wrote:
> > Looks like instrumentation during early boot. I worked with Boris offline to
> > exclude arch/x86/kernel/cc_platform.c from some of the instrumentation and
> > that allowed an allyesconfig to boot.
>
> And here's the lineup I have so far, I'd appreciate it if ppc and s390 folks
> could run it too:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/bp/bp.git/log/?h=rc2-cc

Still broken for me with allyesconfig.

gcc version 11.2.0 (Gentoo 11.2.0 p1)
GNU ld (Gentoo 2.37_p1 p0) 2.37

I still believe calling cc_platform_has() from __startup_64() is totally
broken as it lacks proper wrapping while accessing global variables.

I think sme_get_me_mask() has the same problem. I just happened to work
(until next compiler update).

This hack makes kernel boot again:

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index f98c76a1d16c..e9110a44bf1b 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -285,7 +285,7 @@ unsigned long __head __startup_64(unsigned long physaddr,
* there is no need to zero it after changing the memory encryption
* attribute.
*/
- if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
+ if (0 && cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
vaddr = (unsigned long)__start_bss_decrypted;
vaddr_end = (unsigned long)__end_bss_decrypted;
for (; vaddr < vaddr_end; vaddr += PMD_SIZE) {
diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c
index eff4d19f9cb4..91638ed0b1db 100644
--- a/arch/x86/mm/mem_encrypt_identity.c
+++ b/arch/x86/mm/mem_encrypt_identity.c
@@ -288,7 +288,7 @@ void __init sme_encrypt_kernel(struct boot_params *bp)
unsigned long pgtable_area_len;
unsigned long decrypted_base;

- if (!cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
+ if (1 || !cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
return;

/*
--
Kirill A. Shutemov