linux-kernel - [PATCH V2 7/7] x86/entry: Convert SWAPGS to swapgs and remove the definition of SWAPGS

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Date:   Thu,  3 Mar 2022 11:54:34 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, Lai Jiangshan <jiangshan.ljs@...group.com>,
        xen-devel@...ts.xenproject.org, Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Juergen Gross <jgross@...e.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "Kirill A. Shutemov" <kirill@...temov.name>
Subject: [PATCH V2 7/7] x86/entry: Convert SWAPGS to swapgs and remove the definition of SWAPGS

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

XENPV doesn't use swapgs_restore_regs_and_return_to_usermode(),
error_entry() and entry_SYSENTER_compat(), so the PV-awared SWAPGS in
them can be changed to swapgs.  There is no user of the SWAPGS anymore
after this change.

The INTERRUPT_RETURN in swapgs_restore_regs_and_return_to_usermode()
is also converted.

Cc: xen-devel@...ts.xenproject.org
Reviewed-by: Juergen Gross <jgross@...e.com>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@...group.com>
---
 arch/x86/entry/entry_64.S        | 10 +++++-----
 arch/x86/entry/entry_64_compat.S |  2 +-
 arch/x86/include/asm/irqflags.h  |  2 --
 3 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 88b61f310289..d9c885400034 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -644,8 +644,8 @@ SYM_INNER_LABEL(swapgs_restore_regs_and_return_to_usermode, SYM_L_GLOBAL)
 
 	/* Restore RDI. */
 	popq	%rdi
-	SWAPGS
-	INTERRUPT_RETURN
+	swapgs
+	jmp	native_iret
 
 
 SYM_INNER_LABEL(restore_regs_and_return_to_kernel, SYM_L_GLOBAL)
@@ -1007,7 +1007,7 @@ SYM_CODE_START_LOCAL(error_entry)
 	 * We entered from user mode or we're pretending to have entered
 	 * from user mode due to an IRET fault.
 	 */
-	SWAPGS
+	swapgs
 	FENCE_SWAPGS_USER_ENTRY
 	/* We have user CR3.  Change to kernel CR3. */
 	SWITCH_TO_KERNEL_CR3 scratch_reg=%rax
@@ -1039,7 +1039,7 @@ SYM_CODE_START_LOCAL(error_entry)
 	 * gsbase and proceed.  We'll fix up the exception and land in
 	 * .Lgs_change's error handler with kernel gsbase.
 	 */
-	SWAPGS
+	swapgs
 
 	/*
 	 * Issue an LFENCE to prevent GS speculation, regardless of whether it is a
@@ -1060,7 +1060,7 @@ SYM_CODE_START_LOCAL(error_entry)
 	 * We came from an IRET to user mode, so we have user
 	 * gsbase and CR3.  Switch to kernel gsbase and CR3:
 	 */
-	SWAPGS
+	swapgs
 	FENCE_SWAPGS_USER_ENTRY
 	SWITCH_TO_KERNEL_CR3 scratch_reg=%rax
 
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index a4fcea0cab14..72e017c3941f 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -49,7 +49,7 @@
 SYM_CODE_START(entry_SYSENTER_compat)
 	UNWIND_HINT_EMPTY
 	/* Interrupts are off on entry. */
-	SWAPGS
+	swapgs
 
 	pushq	%rax
 	SWITCH_TO_KERNEL_CR3 scratch_reg=%rax
diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
index 87761396e8cc..ac2e4cc47210 100644
--- a/arch/x86/include/asm/irqflags.h
+++ b/arch/x86/include/asm/irqflags.h
@@ -140,13 +140,11 @@ static __always_inline void arch_local_irq_restore(unsigned long flags)
 #else
 #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
-- 
2.19.1.6.gb485710b