linux-kernel - [PATCHv2] x86/paravirt: Fix build PARAVIRT_XXL=y without XEN

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Date:   Tue, 30 Nov 2021 21:55:32 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
Cc:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Juergen Gross <jgross@...e.com>, Deep Shah <sdeep@...are.com>,
        "VMware, Inc." <pv-drivers@...are.com>
Subject: [PATCHv2] x86/paravirt: Fix build PARAVIRT_XXL=y without XEN_PV

Kernel fails to compile with PARAVIRT_XXL=y if XEN_PV is not enabled:

	ld.lld: error: undefined symbol: xen_iret

It happens because INTERRUPT_RETURN defined to use xen_iret if
CONFIG_PARAVIRT_XXL enabled regardless of CONFIG_XEN_PV.

The issue is not visible in the current kernel because CONFIG_XEN_PV is
the only user of CONFIG_PARAVIRT_XXL and there's no way to enable them
separately.

Rework code to define INTERRUPT_RETURN based on CONFIG_XEN_PV, not
CONFIG_PARAVIRT_XXL.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Reviewed-by: Juergen Gross <jgross@...e.com>
Cc: Deep Shah <sdeep@...are.com>
Cc: "VMware, Inc." <pv-drivers@...are.com>
---
 v2:
  - Drop mention of TDX. TDX will not use PARAVIRT_XXL, but the patch is
    still valid.
  - Reviewed-by from Juergen;
---
 arch/x86/include/asm/irqflags.h | 7 +++++--
 arch/x86/include/asm/paravirt.h | 5 -----
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
index c5ce9845c999..87761396e8cc 100644
--- a/arch/x86/include/asm/irqflags.h
+++ b/arch/x86/include/asm/irqflags.h
@@ -114,8 +114,6 @@ static __always_inline unsigned long arch_local_irq_save(void)
 #define SAVE_FLAGS		pushfq; popq %rax
 #endif
 
-#define INTERRUPT_RETURN	jmp native_iret
-
 #endif
 
 #endif /* __ASSEMBLY__ */
@@ -143,8 +141,13 @@ static __always_inline void arch_local_irq_restore(unsigned long flags)
 #ifdef CONFIG_X86_64
 #ifdef CONFIG_XEN_PV
 #define SWAPGS	ALTERNATIVE "swapgs", "", X86_FEATURE_XENPV
+#define INTERRUPT_RETURN						\
+	ANNOTATE_RETPOLINE_SAFE;					\
+	ALTERNATIVE_TERNARY("jmp *paravirt_iret(%rip);",		\
+		X86_FEATURE_XENPV, "jmp xen_iret;", "jmp native_iret;")
 #else
 #define SWAPGS	swapgs
+#define INTERRUPT_RETURN	jmp native_iret
 #endif
 #endif
 #endif /* !__ASSEMBLY__ */
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 21c4a694ca11..27d276232c80 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -752,11 +752,6 @@ extern void default_banner(void);
 #define PARA_SITE(ptype, ops)	_PVSITE(ptype, ops, .quad, 8)
 #define PARA_INDIRECT(addr)	*addr(%rip)
 
-#define INTERRUPT_RETURN						\
-	ANNOTATE_RETPOLINE_SAFE;					\
-	ALTERNATIVE_TERNARY("jmp *paravirt_iret(%rip);",		\
-		X86_FEATURE_XENPV, "jmp xen_iret;", "jmp native_iret;")
-
 #ifdef CONFIG_DEBUG_ENTRY
 .macro PARA_IRQ_save_fl
 	PARA_SITE(PARA_PATCH(PV_IRQ_save_fl),
-- 
2.32.0