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

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Date:   Fri, 10 Nov 2023 15:06:01 +0300
From:   kirill.shutemov@...ux.intel.com
To:     Jeremi Piotrowski <jpiotrowski@...ux.microsoft.com>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        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>, 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,
        sashal@...nel.org
Subject: Re: [PATCH] x86/mm: Check cc_vendor when printing memory encryption
 info

On Thu, Nov 09, 2023 at 07:41:33PM +0100, Jeremi Piotrowski wrote:
> It's not disregard, the way the kernel behaves in this case is correct except
> for the error in reporting CPU vendor. Users care about seeing the correct
> information in dmesg.

I think it is wrong place to advertise CoCo features. It better fits into
Intel/AMD-specific code that knows better what it is running on. Inferring
it from generic code has been proved problematic as you showed.

Maybe just remove incorrect info and that's it?

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index c290c55b632b..f573a97c0524 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -40,42 +40,6 @@ bool force_dma_unencrypted(struct device *dev)
 	return false;
 }
 
-static void print_mem_encrypt_feature_info(void)
-{
-	pr_info("Memory Encryption Features active:");
-
-	if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) {
-		pr_cont(" Intel TDX\n");
-		return;
-	}
-
-	pr_cont(" AMD");
-
-	/* Secure Memory Encryption */
-	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) {
-		/*
-		 * SME is mutually exclusive with any of the SEV
-		 * features below.
-		 */
-		pr_cont(" SME\n");
-		return;
-	}
-
-	/* Secure Encrypted Virtualization */
-	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
-		pr_cont(" SEV");
-
-	/* Encrypted Register State */
-	if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
-		pr_cont(" SEV-ES");
-
-	/* Secure Nested Paging */
-	if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
-		pr_cont(" SEV-SNP");
-
-	pr_cont("\n");
-}
-
 /* Architecture __weak replacement functions */
 void __init mem_encrypt_init(void)
 {
@@ -85,7 +49,7 @@ void __init mem_encrypt_init(void)
 	/* Call into SWIOTLB to update the SWIOTLB DMA buffers */
 	swiotlb_update_mem_attributes();
 
-	print_mem_encrypt_feature_info();
+	pr_info("Memory Encryption is active\n");
 }
 
 void __init mem_encrypt_setup_arch(void)
-- 
  Kiryl Shutsemau / Kirill A. Shutemov