crypto: x86/sha1 - re-enable the AVX variant

Commit 7c1da8d "crypto: sha - SHA1 transform x86_64 AVX2"
accidentally disabled the AVX variant by making the avx_usable() test
not only fail in case the CPU doesn't support AVX or OSXSAVE but also
if it doesn't support AVX2.

Fix that regression by splitting up the AVX/AVX2 test into two
functions. Also test for the BMI1 extension in the avx2_usable() test
as the AVX2 implementation not only makes use of BMI2 but also BMI1
instructions.

Cc: Chandramouli Narayanan <mouli@linux.intel.com>
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Reviewed-by: H. Peter Anvin <hpa@linux.intel.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/x86/crypto/sha1_ssse3_glue.c

@@ -208,11 +208,7 @@ static bool __init avx_usable(void)
 {
 	u64 xcr0;
 
-#if defined(CONFIG_AS_AVX2)
-	if (!cpu_has_avx || !cpu_has_avx2 || !cpu_has_osxsave)
-#else
 	if (!cpu_has_avx || !cpu_has_osxsave)
-#endif
 		return false;
 
 	xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
@@ -224,11 +220,23 @@ static bool __init avx_usable(void)
 
 	return true;
 }
+
+#ifdef CONFIG_AS_AVX2
+static bool __init avx2_usable(void)
+{
+	if (avx_usable() && cpu_has_avx2 && boot_cpu_has(X86_FEATURE_BMI1) &&
+	    boot_cpu_has(X86_FEATURE_BMI2))
+		return true;
+
+	return false;
+}
+#endif
 #endif
 
 static int __init sha1_ssse3_mod_init(void)
 {
 	char *algo_name;
+
 	/* test for SSSE3 first */
 	if (cpu_has_ssse3) {
 		sha1_transform_asm = sha1_transform_ssse3;
@@ -238,13 +246,11 @@ static int __init sha1_ssse3_mod_init(void)
 #ifdef CONFIG_AS_AVX
 	/* allow AVX to override SSSE3, it's a little faster */
 	if (avx_usable()) {
-		if (cpu_has_avx) {
-			sha1_transform_asm = sha1_transform_avx;
-			algo_name = "AVX";
-		}
+		sha1_transform_asm = sha1_transform_avx;
+		algo_name = "AVX";
 #ifdef CONFIG_AS_AVX2
-		if (cpu_has_avx2 && boot_cpu_has(X86_FEATURE_BMI2)) {
-			/* allow AVX2 to override AVX, it's a little faster */
+		/* allow AVX2 to override AVX, it's a little faster */
+		if (avx2_usable()) {
 			sha1_transform_asm = sha1_apply_transform_avx2;
 			algo_name = "AVX2";
 		}