linux-kernel - [tip: objtool/core] x86/xen: Make read

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Date:   Fri, 17 Sep 2021 12:58:09 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Juergen Gross <jgross@...e.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: objtool/core] x86/xen: Make read_cr2() noinstr

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     0a53c9acf4da51a75392b0b543ce5eaae78a567f
Gitweb:        https://git.kernel.org/tip/0a53c9acf4da51a75392b0b543ce5eaae78a567f
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Thu, 24 Jun 2021 11:41:13 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Fri, 17 Sep 2021 13:11:50 +02:00

x86/xen: Make read_cr2() noinstr

vmlinux.o: warning: objtool: pv_ops[41]: native_read_cr2
vmlinux.o: warning: objtool: pv_ops[41]: xen_read_cr2
vmlinux.o: warning: objtool: pv_ops[41]: xen_read_cr2_direct
vmlinux.o: warning: objtool: exc_double_fault()+0x15: call to pv_ops[41]() leaves .noinstr.text section

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Juergen Gross <jgross@...e.com>
Link: https://lore.kernel.org/r/20210624095148.500331616@infradead.org
---
 arch/x86/include/asm/paravirt.h | 2 +-
 arch/x86/kernel/paravirt.c      | 7 ++++++-
 arch/x86/xen/xen-asm.S          | 2 ++
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index a13a9a3..8878065 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -133,7 +133,7 @@ static inline void write_cr0(unsigned long x)
 	PVOP_VCALL1(cpu.write_cr0, x);
 }
 
-static inline unsigned long read_cr2(void)
+static __always_inline unsigned long read_cr2(void)
 {
 	return PVOP_ALT_CALLEE0(unsigned long, mmu.read_cr2,
 				"mov %%cr2, %%rax;",
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 04cafc0..e351014 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -218,6 +218,11 @@ void paravirt_end_context_switch(struct task_struct *next)
 	if (test_and_clear_ti_thread_flag(task_thread_info(next), TIF_LAZY_MMU_UPDATES))
 		arch_enter_lazy_mmu_mode();
 }
+
+static noinstr unsigned long pv_native_read_cr2(void)
+{
+	return native_read_cr2();
+}
 #endif
 
 enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
@@ -298,7 +303,7 @@ struct paravirt_patch_template pv_ops = {
 	.mmu.exit_mmap		= paravirt_nop,
 
 #ifdef CONFIG_PARAVIRT_XXL
-	.mmu.read_cr2		= __PV_IS_CALLEE_SAVE(native_read_cr2),
+	.mmu.read_cr2		= __PV_IS_CALLEE_SAVE(pv_native_read_cr2),
 	.mmu.write_cr2		= native_write_cr2,
 	.mmu.read_cr3		= __native_read_cr3,
 	.mmu.write_cr3		= native_write_cr3,
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S
index 1e62644..aef4a1e 100644
--- a/arch/x86/xen/xen-asm.S
+++ b/arch/x86/xen/xen-asm.S
@@ -102,6 +102,7 @@ SYM_FUNC_START(check_events)
 	ret
 SYM_FUNC_END(check_events)
 
+.pushsection .noinstr.text, "ax"
 SYM_FUNC_START(xen_read_cr2)
 	FRAME_BEGIN
 	_ASM_MOV PER_CPU_VAR(xen_vcpu), %_ASM_AX
@@ -116,6 +117,7 @@ SYM_FUNC_START(xen_read_cr2_direct)
 	FRAME_END
 	ret
 SYM_FUNC_END(xen_read_cr2_direct);
+.popsection
 
 .macro xen_pv_trap name
 SYM_CODE_START(xen_\name)