[PATCHv2 2/5] x86/tme: Detect if TME and MKTME is activated by BIOS

[Kirill A. Shutemov]

IA32_TME_ACTIVATE MSR (0x982) can be used to check if BIOS has enabled
TME and MKTME. It includes which encryption policy/algorithm is selected
for TME or available for MKTME. For MKTME, the MSR also enumerates how
many KeyIDs are available.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 arch/x86/kernel/cpu/intel.c | 94 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 319bf989fad1..5f8e37675329 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -506,6 +506,97 @@ static void detect_vmx_virtcap(struct cpuinfo_x86 *c)
 	}
 }
 
+#define MSR_IA32_TME_ACTIVATE		0x982
+
+#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
+
+#define MKTME_ENABLED		0
+#define MKTME_DISABLED		1
+#define MKTME_UNINITIALIZED	2
+static int mktme_status = MKTME_UNINITIALIZED;
+
+static void detect_keyid_bits(struct cpuinfo_x86 *c, u64 tme_activate)
+{
+	int keyid_bits = 0, nr_keyids = 0;
+
+	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;
+	}
+
+	/*
+	 * Exclude KeyID bits from physical address bits.
+	 *
+	 * We have to do this even if we are not going to use KeyID bits
+	 * ourself. VM guests still have to know that these bits are not usable
+	 * for physical address.
+	 */
+	c->x86_phys_bits -= keyid_bits;
+}
+
+static void detect_tme(struct cpuinfo_x86 *c)
+{
+	u64 tme_activate, tme_policy, tme_crypto_algs;
+	static u64 tme_activate_cpu0 = 0;
+
+	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: configuation 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;
+		return;
+	}
+
+	if (mktme_status != MKTME_UNINITIALIZED)
+		return detect_keyid_bits(c, tme_activate);
+
+	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(c, tme_activate);
+}
+
 static void init_intel_energy_perf(struct cpuinfo_x86 *c)
 {
 	u64 epb;
@@ -676,6 +767,9 @@ static void init_intel(struct cpuinfo_x86 *c)
 	if (cpu_has(c, X86_FEATURE_VMX))
 		detect_vmx_virtcap(c);
 
+	if (cpu_has(c, X86_FEATURE_TME))
+		detect_tme(c);
+
 	init_intel_energy_perf(c);
 
 	init_intel_misc_features(c);
-- 
2.15.1