Merge tag 'x86-urgent-2024-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Ingo Molnar:

 - Make the CPU_MITIGATIONS=n interaction with conflicting
   mitigation-enabling boot parameters a bit saner.

 - Re-enable CPU mitigations by default on non-x86

 - Fix TDX shared bit propagation on mprotect()

 - Fix potential show_regs() system hang when PKE initialization
   is not fully finished yet.

 - Add the 0x10-0x1f model IDs to the Zen5 range

 - Harden #VC instruction emulation some more

* tag 'x86-urgent-2024-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  cpu: Ignore "mitigations" kernel parameter if CPU_MITIGATIONS=n
  cpu: Re-enable CPU mitigations by default for !X86 architectures
  x86/tdx: Preserve shared bit on mprotect()
  x86/cpu: Fix check for RDPKRU in __show_regs()
  x86/CPU/AMD: Add models 0x10-0x1f to the Zen5 range
  x86/sev: Check for MWAITX and MONITORX opcodes in the #VC handler

Author: torvalds

Documentation/admin-guide/kernel-parameters.txt

@@ -3423,6 +3423,9 @@
 			arch-independent options, each of which is an
 			aggregation of existing arch-specific options.
 
+			Note, "mitigations" is supported if and only if the
+			kernel was built with CPU_MITIGATIONS=y.
+
 			off
 				Disable all optional CPU mitigations.  This
 				improves system performance, but it may also

arch/Kconfig

@@ -9,6 +9,14 @@
 #
 source "arch/$(SRCARCH)/Kconfig"
 
+config ARCH_CONFIGURES_CPU_MITIGATIONS
+	bool
+
+if !ARCH_CONFIGURES_CPU_MITIGATIONS
+config CPU_MITIGATIONS
+	def_bool y
+endif
+
 menu "General architecture-dependent options"
 
 config ARCH_HAS_SUBPAGE_FAULTS

arch/x86/Kconfig

@@ -62,6 +62,7 @@ config X86
 	select ACPI_HOTPLUG_CPU			if ACPI_PROCESSOR && HOTPLUG_CPU
 	select ARCH_32BIT_OFF_T			if X86_32
 	select ARCH_CLOCKSOURCE_INIT
+	select ARCH_CONFIGURES_CPU_MITIGATIONS
 	select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
 	select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
 	select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64
@@ -2488,17 +2489,21 @@ config PREFIX_SYMBOLS
 	def_bool y
 	depends on CALL_PADDING && !CFI_CLANG
 
-menuconfig SPECULATION_MITIGATIONS
-	bool "Mitigations for speculative execution vulnerabilities"
+menuconfig CPU_MITIGATIONS
+	bool "Mitigations for CPU vulnerabilities"
 	default y
 	help
-	  Say Y here to enable options which enable mitigations for
-	  speculative execution hardware vulnerabilities.
+	  Say Y here to enable options which enable mitigations for hardware
+	  vulnerabilities (usually related to speculative execution).
+	  Mitigations can be disabled or restricted to SMT systems at runtime
+	  via the "mitigations" kernel parameter.
 
-	  If you say N, all mitigations will be disabled. You really
-	  should know what you are doing to say so.
+	  If you say N, all mitigations will be disabled.  This CANNOT be
+	  overridden at runtime.
 
-if SPECULATION_MITIGATIONS
+	  Say 'Y', unless you really know what you are doing.
+
+if CPU_MITIGATIONS
 
 config MITIGATION_PAGE_TABLE_ISOLATION
 	bool "Remove the kernel mapping in user mode"

arch/x86/include/asm/coco.h

@@ -25,6 +25,7 @@ u64 cc_mkdec(u64 val);
 void cc_random_init(void);
 #else
 #define cc_vendor (CC_VENDOR_NONE)
+static const u64 cc_mask = 0;
 
 static inline u64 cc_mkenc(u64 val)
 {

arch/x86/include/asm/pgtable_types.h

@@ -148,7 +148,7 @@
 #define _COMMON_PAGE_CHG_MASK	(PTE_PFN_MASK | _PAGE_PCD | _PAGE_PWT |	\
 				 _PAGE_SPECIAL | _PAGE_ACCESSED |	\
 				 _PAGE_DIRTY_BITS | _PAGE_SOFT_DIRTY |	\
-				 _PAGE_DEVMAP | _PAGE_ENC | _PAGE_UFFD_WP)
+				 _PAGE_DEVMAP | _PAGE_CC | _PAGE_UFFD_WP)
 #define _PAGE_CHG_MASK	(_COMMON_PAGE_CHG_MASK | _PAGE_PAT)
 #define _HPAGE_CHG_MASK (_COMMON_PAGE_CHG_MASK | _PAGE_PSE | _PAGE_PAT_LARGE)
 
@@ -173,6 +173,7 @@ enum page_cache_mode {
 };
 #endif
 
+#define _PAGE_CC		(_AT(pteval_t, cc_mask))
 #define _PAGE_ENC		(_AT(pteval_t, sme_me_mask))
 
 #define _PAGE_CACHE_MASK	(_PAGE_PWT | _PAGE_PCD | _PAGE_PAT)

arch/x86/kernel/cpu/amd.c

@@ -459,8 +459,7 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
 
 	case 0x1a:
 		switch (c->x86_model) {
-		case 0x00 ... 0x0f:
-		case 0x20 ... 0x2f:
+		case 0x00 ... 0x2f:
 		case 0x40 ... 0x4f:
 		case 0x70 ... 0x7f:
 			setup_force_cpu_cap(X86_FEATURE_ZEN5);

arch/x86/kernel/process_64.c

@@ -139,7 +139,7 @@ void __show_regs(struct pt_regs *regs, enum show_regs_mode mode,
 		       log_lvl, d3, d6, d7);
 	}
 
-	if (cpu_feature_enabled(X86_FEATURE_OSPKE))
+	if (cr4 & X86_CR4_PKE)
 		printk("%sPKRU: %08x\n", log_lvl, read_pkru());
 }
 

arch/x86/kernel/sev-shared.c

@@ -1203,12 +1203,14 @@ static enum es_result vc_check_opcode_bytes(struct es_em_ctxt *ctxt,
 		break;
 
 	case SVM_EXIT_MONITOR:
-		if (opcode == 0x010f && modrm == 0xc8)
+		/* MONITOR and MONITORX instructions generate the same error code */
+		if (opcode == 0x010f && (modrm == 0xc8 || modrm == 0xfa))
 			return ES_OK;
 		break;
 
 	case SVM_EXIT_MWAIT:
-		if (opcode == 0x010f && modrm == 0xc9)
+		/* MWAIT and MWAITX instructions generate the same error code */
+		if (opcode == 0x010f && (modrm == 0xc9 || modrm == 0xfb))
 			return ES_OK;
 		break;
 

include/linux/cpu.h

@@ -221,7 +221,18 @@ void cpuhp_report_idle_dead(void);
 static inline void cpuhp_report_idle_dead(void) { }
 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 
+#ifdef CONFIG_CPU_MITIGATIONS
 extern bool cpu_mitigations_off(void);
 extern bool cpu_mitigations_auto_nosmt(void);
+#else
+static inline bool cpu_mitigations_off(void)
+{
+	return true;
+}
+static inline bool cpu_mitigations_auto_nosmt(void)
+{
+	return false;
+}
+#endif
 
 #endif /* _LINUX_CPU_H_ */

kernel/cpu.c

@@ -3196,6 +3196,7 @@ void __init boot_cpu_hotplug_init(void)
 	this_cpu_write(cpuhp_state.target, CPUHP_ONLINE);
 }
 
+#ifdef CONFIG_CPU_MITIGATIONS
 /*
  * These are used for a global "mitigations=" cmdline option for toggling
  * optional CPU mitigations.
@@ -3206,9 +3207,7 @@ enum cpu_mitigations {
 	CPU_MITIGATIONS_AUTO_NOSMT,
 };
 
-static enum cpu_mitigations cpu_mitigations __ro_after_init =
-	IS_ENABLED(CONFIG_SPECULATION_MITIGATIONS) ? CPU_MITIGATIONS_AUTO :
-						     CPU_MITIGATIONS_OFF;
+static enum cpu_mitigations cpu_mitigations __ro_after_init = CPU_MITIGATIONS_AUTO;
 
 static int __init mitigations_parse_cmdline(char *arg)
 {
@@ -3224,7 +3223,6 @@ static int __init mitigations_parse_cmdline(char *arg)
 
 	return 0;
 }
-early_param("mitigations", mitigations_parse_cmdline);
 
 /* mitigations=off */
 bool cpu_mitigations_off(void)
@@ -3239,3 +3237,11 @@ bool cpu_mitigations_auto_nosmt(void)
 	return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
 }
 EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);
+#else
+static int __init mitigations_parse_cmdline(char *arg)
+{
+	pr_crit("Kernel compiled without mitigations, ignoring 'mitigations'; system may still be vulnerable\n");
+	return 0;
+}
+#endif
+early_param("mitigations", mitigations_parse_cmdline);