[PATCH v2 0/2] Remove unneeded MKTME detection

[PATCH v2 0/2] Remove unneeded MKTME detection

[alison.schofield]

From: Alison Schofield <alison.schofield@intel.com>

Changes in v2:
- Print the phys_addr bits reduction when BIOS enables MKTME (Kai)
- Remove init of keyid_bits (Kirill)
- Pick up Acked-by tags (Kirill, Kai)
- Update Patch 1 commit message phys addr bits note
- Rebase to latest tiptree
- Add note in this cover letter saying patches are independent

Link to v1: 
https://lore.kernel.org/all/cover.1713929290.git.alison.schofield@intel.com/


Begin original cover letter:
 
MKTME detection was added in anticipation of full kernel support
that never followed. Aside from just good housekeeping, this
cleanup is inspired by users who are confused by the TME/MKTME
messaging during boot.

The first patch cleans up the TME & MKTME detection code and the
second patch removes the unused pconfig code. There are no
dependencies between the 2 patches. The code that Patch 2 removes
is not used anywhere, not even pre-Patch 1.

Testing was done on a platform supporting MKTME using the BIOS
option to enable/disable MKTME prior to boot.

Alison Schofield (2):
  x86/cpu: Remove useless work in detect_tme_early()
  x86/pconfig: Remove unused MKTME pconfig code

 arch/x86/include/asm/intel_pconfig.h | 65 ---------------------
 arch/x86/kernel/cpu/Makefile         |  2 +-
 arch/x86/kernel/cpu/intel.c          | 72 ++++--------------------
 arch/x86/kernel/cpu/intel_pconfig.c  | 84 ----------------------------
 4 files changed, 13 insertions(+), 210 deletions(-)
 delete mode 100644 arch/x86/include/asm/intel_pconfig.h
 delete mode 100644 arch/x86/kernel/cpu/intel_pconfig.c


base-commit: 89948cc11a08639df9f004e866e51f9be887de88
-- 
2.37.3

[PATCH v2 1/2] x86/cpu: Remove useless work in detect_tme_early()

[alison.schofield]

From: Alison Schofield <alison.schofield@intel.com>

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 cb06d8e3d020 ("x86/tme: Detect if TME and MKTME is activated by BIOS")

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/kernel/cpu/intel.c | 72 +++++++------------------------------
 1 file changed, 12 insertions(+), 60 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 3c3e7e5695ba..3ef4e0137d21 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -190,83 +190,35 @@ 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);
 }
 
 static void early_init_intel(struct cpuinfo_x86 *c)
-- 
2.37.3

[PATCH v2 2/2] x86/pconfig: Remove unused MKTME pconfig code

[alison.schofield]

From: Alison Schofield <alison.schofield@intel.com>

Code supporting Intel PCONFIG targets was an early piece of enabling
for MKTME (Multi-Key Total Memory Encryption).

Since MKTME feature enablement did not follow into the kernel, remove
the unused PCONFIG code.

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Kai Huang <kai.huang@intel.com>
---
 arch/x86/include/asm/intel_pconfig.h | 65 ---------------------
 arch/x86/kernel/cpu/Makefile         |  2 +-
 arch/x86/kernel/cpu/intel_pconfig.c  | 84 ----------------------------
 3 files changed, 1 insertion(+), 150 deletions(-)
 delete mode 100644 arch/x86/include/asm/intel_pconfig.h
 delete mode 100644 arch/x86/kernel/cpu/intel_pconfig.c

diff --git a/arch/x86/include/asm/intel_pconfig.h b/arch/x86/include/asm/intel_pconfig.h
deleted file mode 100644
index 994638ef171b..000000000000
--- a/arch/x86/include/asm/intel_pconfig.h
+++ /dev/null
@@ -1,65 +0,0 @@
-#ifndef	_ASM_X86_INTEL_PCONFIG_H
-#define	_ASM_X86_INTEL_PCONFIG_H
-
-#include <asm/asm.h>
-#include <asm/processor.h>
-
-enum pconfig_target {
-	INVALID_TARGET	= 0,
-	MKTME_TARGET	= 1,
-	PCONFIG_TARGET_NR
-};
-
-int pconfig_target_supported(enum pconfig_target target);
-
-enum pconfig_leaf {
-	MKTME_KEY_PROGRAM	= 0,
-	PCONFIG_LEAF_INVALID,
-};
-
-#define PCONFIG ".byte 0x0f, 0x01, 0xc5"
-
-/* Defines and structure for MKTME_KEY_PROGRAM of PCONFIG instruction */
-
-/* mktme_key_program::keyid_ctrl COMMAND, bits [7:0] */
-#define MKTME_KEYID_SET_KEY_DIRECT	0
-#define MKTME_KEYID_SET_KEY_RANDOM	1
-#define MKTME_KEYID_CLEAR_KEY		2
-#define MKTME_KEYID_NO_ENCRYPT		3
-
-/* mktme_key_program::keyid_ctrl ENC_ALG, bits [23:8] */
-#define MKTME_AES_XTS_128	(1 << 8)
-
-/* Return codes from the PCONFIG MKTME_KEY_PROGRAM */
-#define MKTME_PROG_SUCCESS	0
-#define MKTME_INVALID_PROG_CMD	1
-#define MKTME_ENTROPY_ERROR	2
-#define MKTME_INVALID_KEYID	3
-#define MKTME_INVALID_ENC_ALG	4
-#define MKTME_DEVICE_BUSY	5
-
-/* Hardware requires the structure to be 256 byte aligned. Otherwise #GP(0). */
-struct mktme_key_program {
-	u16 keyid;
-	u32 keyid_ctrl;
-	u8 __rsvd[58];
-	u8 key_field_1[64];
-	u8 key_field_2[64];
-} __packed __aligned(256);
-
-static inline int mktme_key_program(struct mktme_key_program *key_program)
-{
-	unsigned long rax = MKTME_KEY_PROGRAM;
-
-	if (!pconfig_target_supported(MKTME_TARGET))
-		return -ENXIO;
-
-	asm volatile(PCONFIG
-		: "=a" (rax), "=b" (key_program)
-		: "0" (rax), "1" (key_program)
-		: "memory", "cc");
-
-	return rax;
-}
-
-#endif	/* _ASM_X86_INTEL_PCONFIG_H */
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index eb4dbcdf41f1..ecd78a61da2e 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -34,7 +34,7 @@ obj-$(CONFIG_PROC_FS)			+= proc.o
 
 obj-$(CONFIG_IA32_FEAT_CTL)		+= feat_ctl.o
 ifdef CONFIG_CPU_SUP_INTEL
-obj-y					+= intel.o intel_pconfig.o tsx.o
+obj-y					+= intel.o tsx.o
 obj-$(CONFIG_PM)			+= intel_epb.o
 endif
 obj-$(CONFIG_CPU_SUP_AMD)		+= amd.o
diff --git a/arch/x86/kernel/cpu/intel_pconfig.c b/arch/x86/kernel/cpu/intel_pconfig.c
deleted file mode 100644
index 5be2b1790282..000000000000
--- a/arch/x86/kernel/cpu/intel_pconfig.c
+++ /dev/null
@@ -1,84 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Intel PCONFIG instruction support.
- *
- * Copyright (C) 2017 Intel Corporation
- *
- * Author:
- *	Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
- */
-#include <linux/bug.h>
-#include <linux/limits.h>
-
-#include <asm/cpufeature.h>
-#include <asm/intel_pconfig.h>
-
-#define	PCONFIG_CPUID			0x1b
-
-#define PCONFIG_CPUID_SUBLEAF_MASK	((1 << 12) - 1)
-
-/* Subleaf type (EAX) for PCONFIG CPUID leaf (0x1B) */
-enum {
-	PCONFIG_CPUID_SUBLEAF_INVALID	= 0,
-	PCONFIG_CPUID_SUBLEAF_TARGETID	= 1,
-};
-
-/* Bitmask of supported targets */
-static u64 targets_supported __read_mostly;
-
-int pconfig_target_supported(enum pconfig_target target)
-{
-	/*
-	 * We would need to re-think the implementation once we get > 64
-	 * PCONFIG targets. Spec allows up to 2^32 targets.
-	 */
-	BUILD_BUG_ON(PCONFIG_TARGET_NR >= 64);
-
-	if (WARN_ON_ONCE(target >= 64))
-		return 0;
-	return targets_supported & (1ULL << target);
-}
-
-static int __init intel_pconfig_init(void)
-{
-	int subleaf;
-
-	if (!boot_cpu_has(X86_FEATURE_PCONFIG))
-		return 0;
-
-	/*
-	 * Scan subleafs of PCONFIG CPUID leaf.
-	 *
-	 * Subleafs of the same type need not to be consecutive.
-	 *
-	 * Stop on the first invalid subleaf type. All subleafs after the first
-	 * invalid are invalid too.
-	 */
-	for (subleaf = 0; subleaf < INT_MAX; subleaf++) {
-		struct cpuid_regs regs;
-
-		cpuid_count(PCONFIG_CPUID, subleaf,
-				&regs.eax, &regs.ebx, &regs.ecx, &regs.edx);
-
-		switch (regs.eax & PCONFIG_CPUID_SUBLEAF_MASK) {
-		case PCONFIG_CPUID_SUBLEAF_INVALID:
-			/* Stop on the first invalid subleaf */
-			goto out;
-		case PCONFIG_CPUID_SUBLEAF_TARGETID:
-			/* Mark supported PCONFIG targets */
-			if (regs.ebx < 64)
-				targets_supported |= (1ULL << regs.ebx);
-			if (regs.ecx < 64)
-				targets_supported |= (1ULL << regs.ecx);
-			if (regs.edx < 64)
-				targets_supported |= (1ULL << regs.edx);
-			break;
-		default:
-			/* Unknown CPUID.PCONFIG subleaf: ignore */
-			break;
-		}
-	}
-out:
-	return 0;
-}
-arch_initcall(intel_pconfig_init);
-- 
2.37.3