linux-kernel - [PATCH v2] x86/sev: Add missing RIP_REL_REF() invocations during sme

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Message-ID: <20241122202322.977678-1-kevinloughlin@google.com>
Date: Fri, 22 Nov 2024 20:23:22 +0000
From: Kevin Loughlin <kevinloughlin@...gle.com>
To: ardb@...nel.org
Cc: ardb+git@...gle.com, bp@...en8.de, kevinloughlin@...gle.com, 
	kirill.shutemov@...ux.intel.com, sidtelang@...gle.com, pgonda@...gle.com, 
	thomas.lendacky@....com, x86@...nel.org, stable@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] x86/sev: Add missing RIP_REL_REF() invocations during sme_enable()

commit 1c811d403afd ("x86/sev: Fix position dependent variable
references in startup code") introduced RIP_REL_REF() to force RIP-
relative accesses to global variables, as needed to prevent crashes
during early SEV/SME startup code. For completeness, RIP_REL_REF()
should be used with additional variables during sme_enable() [0].
Access these vars with RIP_REL_REF() to prevent problem reoccurence.

[0] https://lore.kernel.org/all/CAMj1kXHnA0fJu6zh634=fbJswp59kSRAbhW+ubDGj1+NYwZJ-Q@mail.gmail.com/

Fixes: 1c811d403afd ("x86/sev: Fix position dependent variable references in startup code")
Signed-off-by: Kevin Loughlin <kevinloughlin@...gle.com>
Reviewed-by: Ard Biesheuvel <ardb@...nel.org>
Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
---

v1 -> v2: Fix typo in commit message, add Ard's and Tom's "Reviewed-by"

 arch/x86/mm/mem_encrypt_identity.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c
index e6c7686f443a..9fce5b87b8c5 100644
--- a/arch/x86/mm/mem_encrypt_identity.c
+++ b/arch/x86/mm/mem_encrypt_identity.c
@@ -565,7 +565,7 @@ void __head sme_enable(struct boot_params *bp)
 	}
 
 	RIP_REL_REF(sme_me_mask) = me_mask;
-	physical_mask &= ~me_mask;
-	cc_vendor = CC_VENDOR_AMD;
+	RIP_REL_REF(physical_mask) &= ~me_mask;
+	RIP_REL_REF(cc_vendor) = CC_VENDOR_AMD;
 	cc_set_mask(me_mask);
 }
-- 
2.47.0.371.ga323438b13-goog