[RFC PATCH 5/7] x86/entry: Use atomic-IST-entry for MCE and DB

[Lai Jiangshan <jiangshanlai@gmail.com>]

From: Lai Jiangshan <jiangshan.ljs@antgroup.com>

Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
---
 arch/x86/entry/entry_64.S       | 53 ---------------------------------
 arch/x86/entry/ist_entry.c      |  4 +--
 arch/x86/include/asm/idtentry.h |  4 +--
 3 files changed, 4 insertions(+), 57 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 2bb7ab8512dc..e4ddc793f841 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -621,59 +621,6 @@ _ASM_NOKPROBE(\asmsym)
 SYM_CODE_END(\asmsym)
 .endm
 
-/**
- * idtentry_mce_db - Macro to generate entry stubs for #MC and #DB
- * @vector:		Vector number
- * @asmsym:		ASM symbol for the entry point
- * @cfunc:		C function to be called
- *
- * The macro emits code to set up the kernel context for #MC and #DB
- *
- * If the entry comes from user space it uses the normal entry path
- * including the return to user space work and preemption checks on
- * exit.
- *
- * If hits in kernel mode then it needs to go through the paranoid
- * entry as the exception can hit any random state. No preemption
- * check on exit to keep the paranoid path simple.
- */
-.macro idtentry_mce_db vector asmsym cfunc
-SYM_CODE_START(\asmsym)
-	UNWIND_HINT_IRET_REGS
-	ENDBR
-	ASM_CLAC
-	cld
-
-	pushq	$-1			/* ORIG_RAX: no syscall to restart */
-
-	/*
-	 * If the entry is from userspace, switch stacks and treat it as
-	 * a normal entry.
-	 */
-	testb	$3, CS-ORIG_RAX(%rsp)
-	jnz	.Lfrom_usermode_switch_stack_\@
-
-	PUSH_AND_CLEAR_REGS
-	UNWIND_HINT_REGS
-	ENCODE_FRAME_POINTER
-
-	/* paranoid_entry returns GS information for paranoid_exit in EBX. */
-	call	paranoid_entry
-
-	movq	%rsp, %rdi		/* pt_regs pointer */
-
-	call	\cfunc
-
-	jmp	paranoid_exit
-
-	/* Switch to the regular task stack and use the noist entry point */
-.Lfrom_usermode_switch_stack_\@:
-	idtentry_body noist_\cfunc, has_error_code=0
-
-_ASM_NOKPROBE(\asmsym)
-SYM_CODE_END(\asmsym)
-.endm
-
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 /**
  * idtentry_vc - Macro to generate entry stub for #VC
diff --git a/arch/x86/entry/ist_entry.c b/arch/x86/entry/ist_entry.c
index 407571cc4a8c..946b3b537bd5 100644
--- a/arch/x86/entry/ist_entry.c
+++ b/arch/x86/entry/ist_entry.c
@@ -42,8 +42,8 @@ static __always_inline bool identify_ist_##sym_name(				\
 }
 
 DEFINE_IDENTIFY_IST(NMI, nmi, true)
-DEFINE_IDENTIFY_IST(DB, debug, false)
-DEFINE_IDENTIFY_IST(MCE, machine_check, false)
+DEFINE_IDENTIFY_IST(DB, debug, true)
+DEFINE_IDENTIFY_IST(MCE, machine_check, IS_ENABLED(CONFIG_X86_MCE))
 DEFINE_IDENTIFY_IST(VC, vmm_communication, false)
 
 static __always_inline bool identify_ist(
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index b568f1de6da6..01f3152ffe82 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -454,10 +454,10 @@ __visible noinstr void func(struct pt_regs *regs,			\
 	idtentry_ist vector asm_##func func func has_error_code=0 stack_offset=CEA_stacks_NMI
 
 # define DECLARE_IDTENTRY_MCE(vector, func)				\
-	idtentry_mce_db vector asm_##func func
+	idtentry_ist vector asm_##func func noist_##func has_error_code=0 stack_offset=CEA_stacks_MCE
 
 # define DECLARE_IDTENTRY_DEBUG(vector, func)				\
-	idtentry_mce_db vector asm_##func func
+	idtentry_ist vector asm_##func func noist_##func has_error_code=0 stack_offset=CEA_stacks_DB
 
 # define DECLARE_IDTENTRY_DF(vector, func)				\
 	idtentry_df vector asm_##func func
-- 
2.19.1.6.gb485710b