x86/fred: Move FRED RSP initialization into a separate function

To enable FRED earlier, move the RSP initialization out of
cpu_init_fred_exceptions() into cpu_init_fred_rsps().

This is required as the FRED RSP initialization depends on the availability
of the CPU entry areas which are set up late in trap_init(),

No functional change intended. Marked with Fixes as it's a depedency for
the real fix.

Fixes: 14619d912b65 ("x86/fred: FRED entry/exit and dispatch code")
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240709154048.3543361-3-xin@zytor.com

diff --git a/arch/x86/include/asm/fred.h b/arch/x86/include/asm/fred.h
index e86c7ba32435f5a6956ebab09656c639a21ec53f..66d7dbe2d314c1318006dfe84057358213c205c8 100644 (file)
--- a/arch/x86/include/asm/fred.h
+++ b/arch/x86/include/asm/fred.h
@@ -84,11 +84,13 @@ static __always_inline void fred_entry_from_kvm(unsigned int type, unsigned int
 }
 
 void cpu_init_fred_exceptions(void);
+void cpu_init_fred_rsps(void);
 void fred_complete_exception_setup(void);
 
 #else /* CONFIG_X86_FRED */
 static __always_inline unsigned long fred_event_data(struct pt_regs *regs) { return 0; }
 static inline void cpu_init_fred_exceptions(void) { }
+static inline void cpu_init_fred_rsps(void) { }
 static inline void fred_complete_exception_setup(void) { }
 static __always_inline void fred_entry_from_kvm(unsigned int type, unsigned int vector) { }
 #endif /* CONFIG_X86_FRED */

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 10a5402d829718ccb7657846684258c42de0f7d0..6de12b3c1b049d8646b26e3d3a119f425c18b957 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2195,10 +2195,12 @@ void cpu_init_exception_handling(void)
        /* GHCB needs to be setup to handle #VC. */
        setup_ghcb();
 
-       if (cpu_feature_enabled(X86_FEATURE_FRED))
+       if (cpu_feature_enabled(X86_FEATURE_FRED)) {
                cpu_init_fred_exceptions();
-       else
+               cpu_init_fred_rsps();
+       } else {
                load_current_idt();
+       }
 }
 
 /*

diff --git a/arch/x86/kernel/fred.c b/arch/x86/kernel/fred.c
index 4bcd8791ad96ad84937983ff3beeb880bb671e40..99a134fcd5bf4a63dc4b5430efd735433e86e464 100644 (file)
--- a/arch/x86/kernel/fred.c
+++ b/arch/x86/kernel/fred.c
@@ -32,6 +32,25 @@ void cpu_init_fred_exceptions(void)
               FRED_CONFIG_INT_STKLVL(0) |
               FRED_CONFIG_ENTRYPOINT(asm_fred_entrypoint_user));
 
+       wrmsrl(MSR_IA32_FRED_STKLVLS, 0);
+       wrmsrl(MSR_IA32_FRED_RSP0, 0);
+       wrmsrl(MSR_IA32_FRED_RSP1, 0);
+       wrmsrl(MSR_IA32_FRED_RSP2, 0);
+       wrmsrl(MSR_IA32_FRED_RSP3, 0);
+
+       /* Enable FRED */
+       cr4_set_bits(X86_CR4_FRED);
+       /* Any further IDT use is a bug */
+       idt_invalidate();
+
+       /* Use int $0x80 for 32-bit system calls in FRED mode */
+       setup_clear_cpu_cap(X86_FEATURE_SYSENTER32);
+       setup_clear_cpu_cap(X86_FEATURE_SYSCALL32);
+}
+
+/* Must be called after setup_cpu_entry_areas() */
+void cpu_init_fred_rsps(void)
+{
        /*
         * The purpose of separate stacks for NMI, #DB and #MC *in the kernel*
         * (remember that user space faults are always taken on stack level 0)
@@ -47,13 +66,4 @@ void cpu_init_fred_exceptions(void)
        wrmsrl(MSR_IA32_FRED_RSP1, __this_cpu_ist_top_va(DB));
        wrmsrl(MSR_IA32_FRED_RSP2, __this_cpu_ist_top_va(NMI));
        wrmsrl(MSR_IA32_FRED_RSP3, __this_cpu_ist_top_va(DF));
-
-       /* Enable FRED */
-       cr4_set_bits(X86_CR4_FRED);
-       /* Any further IDT use is a bug */
-       idt_invalidate();
-
-       /* Use int $0x80 for 32-bit system calls in FRED mode */
-       setup_clear_cpu_cap(X86_FEATURE_SYSENTER32);
-       setup_clear_cpu_cap(X86_FEATURE_SYSCALL32);
 }