x86/cpu: Remove useless work in detect_tme_early()

JIRA: https://issues.redhat.com/browse/RHEL-111095

commit 98b83cf
Author: Alison Schofield <alison.schofield@intel.com>
Date:   Mon May 6 21:24:21 2024 -0700

    x86/cpu: Remove useless work in detect_tme_early()

    TME (Total Memory Encryption) and MKTME (Multi-Key Total Memory
    Encryption) BIOS detection were introduced together here [1] and
    are loosely coupled in the Intel CPU init code.

    TME is a hardware only feature and its BIOS status is all that needs
    to be shared with the kernel user: enabled or disabled. The TME
    algorithm the BIOS is using and whether or not the kernel recognizes
    that algorithm is useless to the kernel user.

    MKTME is a hardware feature that requires kernel support. MKTME
    detection code was added in advance of broader kernel support for
    MKTME that never followed. So, rather than continuing to spew
    needless and confusing messages about BIOS MKTME status, remove
    most of the MKTME pieces from detect_tme_early().

    Keep one useful message: alert the user when BIOS enabled MKTME
    reduces the available physical address bits. Recovery of the MKTME
    consumed bits requires a reboot with MKTME disabled in BIOS.

    There is no functional change for the user, only a change in boot
    messages. Below is one example when both TME and MKTME are enabled
    in BIOS with AES_XTS_256 which is unknown to the detect tme code.

    Before:
    [] x86/tme: enabled by BIOS
    [] x86/tme: Unknown policy is active: 0x2
    [] x86/mktme: No known encryption algorithm is supported: 0x4
    [] x86/mktme: enabled by BIOS
    [] x86/mktme: 127 KeyIDs available

    After:
    [] x86/tme: enabled by BIOS
    [] x86/mktme: BIOS enable: x86_phys_bits reduced by 8

    [1]
    commit cb06d8e ("x86/tme: Detect if TME and MKTME is activated by BIOS")

    Signed-off-by: Alison Schofield <alison.schofield@intel.com>
    Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
    Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Link: https://lore.kernel.org/all/86dfdf6ced8c9b790f9376bf6c7e22b5608f47c2.1715054189.git.alison.schofield%40intel.com

Signed-off-by: Frank Liang <xiliang@redhat.com>

Author: liangxiao1

arch/x86/kernel/cpu/intel.c

@@ -187,83 +187,35 @@ static bool bad_spectre_microcode(struct cpuinfo_x86 *c)
 #define TME_ACTIVATE_LOCKED(x)		(x & 0x1)
 #define TME_ACTIVATE_ENABLED(x)		(x & 0x2)
 
-#define TME_ACTIVATE_POLICY(x)		((x >> 4) & 0xf)	/* Bits 7:4 */
-#define TME_ACTIVATE_POLICY_AES_XTS_128	0
-
 #define TME_ACTIVATE_KEYID_BITS(x)	((x >> 32) & 0xf)	/* Bits 35:32 */
 
-#define TME_ACTIVATE_CRYPTO_ALGS(x)	((x >> 48) & 0xffff)	/* Bits 63:48 */
-#define TME_ACTIVATE_CRYPTO_AES_XTS_128	1
-
-/* Values for mktme_status (SW only construct) */
-#define MKTME_ENABLED			0
-#define MKTME_DISABLED			1
-#define MKTME_UNINITIALIZED		2
-static int mktme_status = MKTME_UNINITIALIZED;
-
 static void detect_tme_early(struct cpuinfo_x86 *c)
 {
-	u64 tme_activate, tme_policy, tme_crypto_algs;
-	int keyid_bits = 0, nr_keyids = 0;
-	static u64 tme_activate_cpu0 = 0;
+	u64 tme_activate;
+	int keyid_bits;
 
 	rdmsrl(MSR_IA32_TME_ACTIVATE, tme_activate);
 
-	if (mktme_status != MKTME_UNINITIALIZED) {
-		if (tme_activate != tme_activate_cpu0) {
-			/* Broken BIOS? */
-			pr_err_once("x86/tme: configuration is inconsistent between CPUs\n");
-			pr_err_once("x86/tme: MKTME is not usable\n");
-			mktme_status = MKTME_DISABLED;
-
-			/* Proceed. We may need to exclude bits from x86_phys_bits. */
-		}
-	} else {
-		tme_activate_cpu0 = tme_activate;
-	}
-
 	if (!TME_ACTIVATE_LOCKED(tme_activate) || !TME_ACTIVATE_ENABLED(tme_activate)) {
 		pr_info_once("x86/tme: not enabled by BIOS\n");
-		mktme_status = MKTME_DISABLED;
 		clear_cpu_cap(c, X86_FEATURE_TME);
 		return;
 	}
-
-	if (mktme_status != MKTME_UNINITIALIZED)
-		goto detect_keyid_bits;
-
-	pr_info("x86/tme: enabled by BIOS\n");
-
-	tme_policy = TME_ACTIVATE_POLICY(tme_activate);
-	if (tme_policy != TME_ACTIVATE_POLICY_AES_XTS_128)
-		pr_warn("x86/tme: Unknown policy is active: %#llx\n", tme_policy);
-
-	tme_crypto_algs = TME_ACTIVATE_CRYPTO_ALGS(tme_activate);
-	if (!(tme_crypto_algs & TME_ACTIVATE_CRYPTO_AES_XTS_128)) {
-		pr_err("x86/mktme: No known encryption algorithm is supported: %#llx\n",
-				tme_crypto_algs);
-		mktme_status = MKTME_DISABLED;
-	}
-detect_keyid_bits:
+	pr_info_once("x86/tme: enabled by BIOS\n");
 	keyid_bits = TME_ACTIVATE_KEYID_BITS(tme_activate);
-	nr_keyids = (1UL << keyid_bits) - 1;
-	if (nr_keyids) {
-		pr_info_once("x86/mktme: enabled by BIOS\n");
-		pr_info_once("x86/mktme: %d KeyIDs available\n", nr_keyids);
-	} else {
-		pr_info_once("x86/mktme: disabled by BIOS\n");
-	}
-
-	if (mktme_status == MKTME_UNINITIALIZED) {
-		/* MKTME is usable */
-		mktme_status = MKTME_ENABLED;
-	}
+	if (!keyid_bits)
+		return;
 
 	/*
-	 * KeyID bits effectively lower the number of physical address
-	 * bits.  Update cpuinfo_x86::x86_phys_bits accordingly.
+	 * KeyID bits are set by BIOS and can be present regardless
+	 * of whether the kernel is using them. They effectively lower
+	 * the number of physical address bits.
+	 *
+	 * Update cpuinfo_x86::x86_phys_bits accordingly.
 	 */
 	c->x86_phys_bits -= keyid_bits;
+	pr_info_once("x86/mktme: BIOS enabled: x86_phys_bits reduced by %d\n",
+		     keyid_bits);
 }
 
 void intel_unlock_cpuid_leafs(struct cpuinfo_x86 *c)