linux-kernel - [PATCH 1/2] x86/fred: Always install system interrupt handler into IDT

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Date: Fri, 21 Jun 2024 21:12:01 +0800
From: "Hou Wenlong" <houwenlong.hwl@...group.com>
To: linux-kernel@...r.kernel.org
Cc: "Lai Jiangshan" <jiangshan.ljs@...group.com>,
  "Hou Wenlong" <houwenlong.hwl@...group.com>,
  "Thomas Gleixner" <tglx@...utronix.de>,
  "Ingo Molnar" <mingo@...hat.com>,
  "Borislav Petkov" <bp@...en8.de>,
  "Dave Hansen" <dave.hansen@...ux.intel.com>,
   <x86@...nel.org>,
  "H. Peter Anvin" <hpa@...or.com>,
  "Xin Li" <xin3.li@...el.com>,
  "Jacob Pan" <jacob.jun.pan@...ux.intel.com>,
  "Rick Edgecombe" <rick.p.edgecombe@...el.com>,
  "Paolo Bonzini" <pbonzini@...hat.com>
Subject: [PATCH 1/2] x86/fred: Always install system interrupt handler into IDT

In sysvec_install(), the system interrupt handler is not installed into
the IDT when the FRED feature is present, but FRED can be disabled
in trap_init(). However, sysvec_install() can be used
before trap_init(), e.g., the HYPERVISOR_CALLBACK_VECTOR handler is
registered in kvm_guest_init(), which is called by setup_arch() before
trap_init(). If FRED is disabled later, then the spurious_interrupt()
handler will be used due to the handler not being installed into the
IDT. Therefore, always install system interrupt handler into IDT.

Fixes: 3810da12710a ("x86/fred: Add a fred= cmdline param")
Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
---
 arch/x86/include/asm/idtentry.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index d4f24499b256..daee9f7765bc 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -470,8 +470,7 @@ static inline void fred_install_sysvec(unsigned int vector, const idtentry_t fun
 #define sysvec_install(vector, function) {				\
 	if (cpu_feature_enabled(X86_FEATURE_FRED))			\
 		fred_install_sysvec(vector, function);			\
-	else								\
-		idt_install_sysvec(vector, asm_##function);		\
+	idt_install_sysvec(vector, asm_##function);			\
 }

 #else /* !__ASSEMBLY__ */
-- 
2.31.1