linux-kernel - [RFC PATCH v2 23/34] x86/extable: Remove new dead code in ex_handler

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Message-ID: <20250422082216.1954310-24-xin@zytor.com>
Date: Tue, 22 Apr 2025 01:22:04 -0700
From: "Xin Li (Intel)" <xin@...or.com>
To: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
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Subject: [RFC PATCH v2 23/34] x86/extable: Remove new dead code in ex_handler_msr()

The MSR read APIs no longer expect RAX or EDX:EAX to be cleared upon
returning from #GP caused by MSR read instructions.

The MSR safe APIs no longer assume -EIO being returned in a register
from #GP caused by MSR instructions.

Remove new dead code due to above changes.

Signed-off-by: Xin Li (Intel) <xin@...or.com>
---
 arch/x86/mm/extable.c | 21 +++++----------------
 1 file changed, 5 insertions(+), 16 deletions(-)

diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 6bf4c2a43c2c..ea3fe7f32772 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -165,7 +165,7 @@ static bool ex_handler_uaccess(const struct exception_table_entry *fixup,
 }
 
 static bool ex_handler_msr(const struct exception_table_entry *fixup,
-			   struct pt_regs *regs, bool wrmsr, bool safe, int reg)
+			   struct pt_regs *regs, bool wrmsr, bool safe)
 {
 	bool imm_insn = is_msr_imm_insn((void *)regs->ip);
 	u32 msr;
@@ -207,17 +207,6 @@ static bool ex_handler_msr(const struct exception_table_entry *fixup,
 		show_stack_regs(regs);
 	}
 
-	if (!wrmsr) {
-		/* Pretend that the read succeeded and returned 0. */
-		regs->ax = 0;
-
-		if (!imm_insn)
-			regs->dx = 0;
-	}
-
-	if (safe)
-		*pt_regs_nr(regs, reg) = -EIO;
-
 	return ex_handler_default(fixup, regs);
 }
 
@@ -395,13 +384,13 @@ int fixup_exception(struct pt_regs *regs, int trapnr, unsigned long error_code,
 		case EX_TYPE_BPF:
 			return ex_handler_bpf(e, regs);
 		case EX_TYPE_WRMSR:
-			return ex_handler_msr(e, regs, true, false, reg);
+			return ex_handler_msr(e, regs, true, false);
 		case EX_TYPE_RDMSR:
-			return ex_handler_msr(e, regs, false, false, reg);
+			return ex_handler_msr(e, regs, false, false);
 		case EX_TYPE_WRMSR_SAFE:
-			return ex_handler_msr(e, regs, true, true, reg);
+			return ex_handler_msr(e, regs, true, true);
 		case EX_TYPE_RDMSR_SAFE:
-			return ex_handler_msr(e, regs, false, true, reg);
+			return ex_handler_msr(e, regs, false, true);
 		case EX_TYPE_WRMSR_IN_MCE:
 			ex_handler_msr_mce(regs, true);
 			break;
-- 
2.49.0