linux-kernel - Re: [PATCH v9 07/22] KVM: VMX: Initialize VMCS FRED fields

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Message-Id: <E5D53B8D-5A2B-4F9C-9071-E0C56A44AE7D@zytor.com>
Date: Thu, 22 Jan 2026 09:22:56 -0800
From: Xin Li <xin@...or.com>
To: Binbin Wu <binbin.wu@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, pbonzini@...hat.com, seanjc@...gle.com,
        corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        luto@...nel.org, peterz@...radead.org, andrew.cooper3@...rix.com,
        chao.gao@...el.com, hch@...radead.org, sohil.mehta@...el.com
Subject: Re: [PATCH v9 07/22] KVM: VMX: Initialize VMCS FRED fields


>> The trouble comes from __this_cpu_ist_top_va():
> 
> Oh, right! 
> Sorry for the noise.

It’s absolutely NOT noise, because we don’t like #ifdef in C file.

With the following additional patch, we can remove this #ifdef CONFIG_X86_64:

diff --git a/arch/x86/include/asm/cpu_entry_area.h b/arch/x86/include/asm/cpu_entry_area.h
index 509e52fc3a0f..c35ef2cb9b8a 100644
--- a/arch/x86/include/asm/cpu_entry_area.h
+++ b/arch/x86/include/asm/cpu_entry_area.h
@@ -8,14 +8,6 @@
 #include <asm/intel_ds.h>
 #include <asm/pgtable_areas.h>
  -#ifdef CONFIG_X86_64
-
-#ifdef CONFIG_AMD_MEM_ENCRYPT
-#define VC_EXCEPTION_STKSZ     EXCEPTION_STKSZ
-#else
-#define VC_EXCEPTION_STKSZ     0
-#endif
-
 /*
  * The exception stack ordering in [cea_]exception_stacks
  */
@@ -26,9 +18,19 @@ enum exception_stack_ordering {
        ESTACK_MCE,
        ESTACK_VC,
        ESTACK_VC2,
+#ifdef CONFIG_X86_64
        N_EXCEPTION_STACKS
+#endif
 };
  +#ifdef CONFIG_X86_64
+
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+#define VC_EXCEPTION_STKSZ     EXCEPTION_STKSZ
+#else
+#define VC_EXCEPTION_STKSZ     0
+#endif
+
 /* Macro to enforce the same ordering and stack sizes */
 #define ESTACKS_MEMBERS(guardsize, optional_stack_size)                \
        char    ESTACK_DF_stack_guard[guardsize];               \
@@ -75,6 +77,11 @@ struct doublefault_stack {
        unsigned long stack[(PAGE_SIZE - sizeof(struct x86_hw_tss)) / sizeof(unsigned long)];
        struct x86_hw_tss tss;
 } __aligned(PAGE_SIZE);
+
+static inline unsigned long __this_cpu_ist_top_va(enum exception_stack_ordering stack)
+{
+       return 0;
+}
 #endif
   /*


Another simpler way to define __this_cpu_ist_top_va() in a VMX header, but
I don’t think it’s the right way.