1 files changed, 28 insertions, 10 deletions

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 087d21734286..c44e6f0c8972 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -61,6 +61,7 @@
 #include <asm/microcode.h>
 #include <asm/intel-family.h>
 #include <asm/cpu_device_id.h>
+#include <asm/fred.h>
 #include <asm/uv/uv.h>
 #include <asm/ia32.h>
 #include <asm/set_memory.h>
@@ -394,9 +395,8 @@ out:
 }
 
 /* These bits should not change their value after CPU init is finished. */
-static const unsigned long cr4_pinned_mask =
-	X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP |
-	X86_CR4_FSGSBASE | X86_CR4_CET;
+static const unsigned long cr4_pinned_mask = X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP |
+					     X86_CR4_FSGSBASE | X86_CR4_CET | X86_CR4_FRED;
 static DEFINE_STATIC_KEY_FALSE_RO(cr_pinning);
 static unsigned long cr4_pinned_bits __ro_after_init;
 
@@ -1976,10 +1976,8 @@ static void wrmsrl_cstar(unsigned long val)
 		wrmsrl(MSR_CSTAR, val);
 }
 
-/* May not be marked __init: used by software suspend */
-void syscall_init(void)
+static inline void idt_syscall_init(void)
 {
-	wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS);
 	wrmsrl(MSR_LSTAR, (unsigned long)entry_SYSCALL_64);
 
 	if (ia32_enabled()) {
@@ -2013,6 +2011,23 @@ void syscall_init(void)
 	       X86_EFLAGS_AC|X86_EFLAGS_ID);
 }
 
+/* May not be marked __init: used by software suspend */
+void syscall_init(void)
+{
+	/* The default user and kernel segments */
+	wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS);
+
+	/*
+	 * Except the IA32_STAR MSR, there is NO need to setup SYSCALL and
+	 * SYSENTER MSRs for FRED, because FRED uses the ring 3 FRED
+	 * entrypoint for SYSCALL and SYSENTER, and ERETU is the only legit
+	 * instruction to return to ring 3 (both sysexit and sysret cause
+	 * #UD when FRED is enabled).
+	 */
+	if (!cpu_feature_enabled(X86_FEATURE_FRED))
+		idt_syscall_init();
+}
+
 #else	/* CONFIG_X86_64 */
 
 #ifdef CONFIG_STACKPROTECTOR
@@ -2116,8 +2131,9 @@ void cpu_init_exception_handling(void)
 	/* paranoid_entry() gets the CPU number from the GDT */
 	setup_getcpu(cpu);
 
-	/* IST vectors need TSS to be set up. */
-	tss_setup_ist(tss);
+	/* For IDT mode, IST vectors need to be set in TSS. */
+	if (!cpu_feature_enabled(X86_FEATURE_FRED))
+		tss_setup_ist(tss);
 	tss_setup_io_bitmap(tss);
 	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
 
@@ -2126,8 +2142,10 @@ void cpu_init_exception_handling(void)
 	/* GHCB needs to be setup to handle #VC. */
 	setup_ghcb();
 
-	/* Finally load the IDT */
-	load_current_idt();
+	if (cpu_feature_enabled(X86_FEATURE_FRED))
+		cpu_init_fred_exceptions();
+	else
+		load_current_idt();
 }
 
 /*