linux-kernel - [PATCH] x86/mm: Check cc_vendor when printing memory encryption info

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Date:   Thu,  9 Nov 2023 08:14:49 -0800
From:   Jeremi Piotrowski <jpiotrowski@...ux.microsoft.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        linux-kernel@...r.kernel.org,
        Michael Kelley <mhklinux@...look.com>,
        Dexuan Cui <decui@...rosoft.com>
Cc:     Jeremi Piotrowski <jpiotrowski@...ux.microsoft.com>,
        linux-hyperv@...r.kernel.org, stefan.bader@...onical.com,
        tim.gardner@...onical.com, roxana.nicolescu@...onical.com,
        cascardo@...onical.com, kys@...rosoft.com, haiyangz@...rosoft.com,
        wei.liu@...nel.org, kirill.shutemov@...ux.intel.com,
        sashal@...nel.org
Subject: [PATCH] x86/mm: Check cc_vendor when printing memory encryption info

Check the value of cc_vendor to see if we're in an Intel TDX protected VM
instead of checking for the TDX_GUEST CPU feature. The rest of the function
already uses the abstractions available in cc_platform.h to check for
confidential computing features. For Intel, cc_vendor is set from
tdx_early_init() or hv_vtom_init(), so the new code correctly handles both
cases. The previous check relied on the Linux-controlled TDX_GUEST CPU feature
which is only set in tdx_early_init().

Signed-off-by: Jeremi Piotrowski <jpiotrowski@...ux.microsoft.com>
---
 arch/x86/mm/mem_encrypt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index c290c55b632b..d3bd39aad8b6 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -44,7 +44,7 @@ static void print_mem_encrypt_feature_info(void)
 {
 	pr_info("Memory Encryption Features active:");
 
-	if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) {
+	if (cc_vendor == CC_VENDOR_INTEL) {
 		pr_cont(" Intel TDX\n");
 		return;
 	}
-- 
2.39.2