linux-kernel - [PATCH v2 2/3] x86/fred: Split FRED RSP initialization into a separate function

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Message-ID: <20240709154048.3543361-3-xin@zytor.com>
Date: Tue,  9 Jul 2024 08:40:47 -0700
From: "Xin Li (Intel)" <xin@...or.com>
To: linux-kernel@...r.kernel.org
Cc: hpa@...or.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, peterz@...radead.org,
        andrew.cooper3@...rix.com, nik.borisov@...e.com,
        houwenlong.hwl@...group.com
Subject: [PATCH v2 2/3] x86/fred: Split FRED RSP initialization into a separate function

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@...or.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 10a5402d8297..6de12b3c1b04 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 4bcd8791ad96..99a134fcd5bf 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));
 
+	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);
 }
-- 
2.45.2