linux-kernel - Re: [PATCH v3 5/8] x86/sme: Replace occurrences of sme_active() with cc_platform

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Message-ID: <20210921212059.wwlytlmxoft4cdth@box.shutemov.name>
Date:   Wed, 22 Sep 2021 00:20:59 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Tom Lendacky <thomas.lendacky@....com>,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        iommu@...ts.linux-foundation.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-graphics-maintainer@...are.com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        kexec@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        Brijesh Singh <brijesh.singh@....com>,
        Joerg Roedel <joro@...tes.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        Christoph Hellwig <hch@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v3 5/8] x86/sme: Replace occurrences of sme_active() with
 cc_platform_has()

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