linux-kernel - [PATCH] crypto: x86/aes-ni: fix AVX detection

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Message-Id: <20211103124614.499580-1-mlevitsk@redhat.com>
Date:   Wed,  3 Nov 2021 14:46:14 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        linux-crypto@...r.kernel.org (open list:CRYPTO API),
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Borislav Petkov <bp@...en8.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH] crypto: x86/aes-ni: fix AVX detection

Fix two semi-theoretical issues that are present.

1. AVX is assumed to be present when AVX2 is present.
 That can be false in a VM.
 This can be considered a hypervisor bug,
 but the kernel should not crash in this case if this is possible.

2. YMM state can be soft disabled in XCR0.

Fix both issues by using 'cpu_has_xfeatures(XFEATURE_MASK_YMM')
to check for usable AVX support.

Fixes: d764593af9249 ("crypto: aesni - AVX and AVX2 version of AESNI-GCM encode and decode")

Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/crypto/aesni-intel_glue.c | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/arch/x86/crypto/aesni-intel_glue.c b/arch/x86/crypto/aesni-intel_glue.c
index 0fc961bef299c..20db1e500ef6f 100644
--- a/arch/x86/crypto/aesni-intel_glue.c
+++ b/arch/x86/crypto/aesni-intel_glue.c
@@ -1147,24 +1147,25 @@ static int __init aesni_init(void)
 	if (!x86_match_cpu(aesni_cpu_id))
 		return -ENODEV;
 #ifdef CONFIG_X86_64
-	if (boot_cpu_has(X86_FEATURE_AVX2)) {
-		pr_info("AVX2 version of gcm_enc/dec engaged.\n");
-		static_branch_enable(&gcm_use_avx);
-		static_branch_enable(&gcm_use_avx2);
-	} else
-	if (boot_cpu_has(X86_FEATURE_AVX)) {
-		pr_info("AVX version of gcm_enc/dec engaged.\n");
+	if (cpu_has_xfeatures(XFEATURE_MASK_YMM, NULL)) {
+
 		static_branch_enable(&gcm_use_avx);
-	} else {
-		pr_info("SSE version of gcm_enc/dec engaged.\n");
-	}
-	if (boot_cpu_has(X86_FEATURE_AVX)) {
+
+		if (boot_cpu_has(X86_FEATURE_AVX2)) {
+			static_branch_enable(&gcm_use_avx2);
+			pr_info("AVX2 version of gcm_enc/dec engaged.\n");
+		} else {
+			pr_info("AVX version of gcm_enc/dec engaged.\n");
+		}
+
 		/* optimize performance of ctr mode encryption transform */
 		static_call_update(aesni_ctr_enc_tfm, aesni_ctr_enc_avx_tfm);
 		pr_info("AES CTR mode by8 optimization enabled\n");
+
+	} else {
+		pr_info("SSE version of gcm_enc/dec engaged.\n");
 	}
 #endif
-
 	err = crypto_register_alg(&aesni_cipher_alg);
 	if (err)
 		return err;
-- 
2.26.3