[PATCH v1 3/4] x86/fred: Split FRED RSP initialization into a separate function

Xin Li (Intel)
2024-07-03T08:55:11Z

To enable FRED earlier, split FRED RSP initialization into a separate
function, as they are initialized with memory from CPU entry areas,
thus their initialization has to be kept after setup_cpu_entry_areas().

No functional change intended.

Signed-off-by: Xin Li (Intel) <xin@zytor.com>
---
arch/x86/include/asm/fred.h | 2 ++
arch/x86/kernel/cpu/common.c | 6 ++++--
arch/x86/kernel/fred.c | 28 +++++++++++++++++++---------
3 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/fred.h b/arch/x86/include/asm/fred.h
index e86c7ba32435..66d7dbe2d314 100644
--- 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 9a904fe7c829..022ae4ba7997 100644
--- 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 b202685b8e77..1788f28754f3 100644
--- 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));

+ wrmsrns(MSR_IA32_FRED_STKLVLS, 0);
+ wrmsrns(MSR_IA32_FRED_RSP0, 0);
+ wrmsrns(MSR_IA32_FRED_RSP1, 0);
+ wrmsrns(MSR_IA32_FRED_RSP2, 0);
+ wrmsrns(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)
wrmsrns(MSR_IA32_FRED_RSP1, __this_cpu_ist_top_va(DB));
wrmsrns(MSR_IA32_FRED_RSP2, __this_cpu_ist_top_va(NMI));
wrmsrns(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);
}
--
2.45.2