linux-kernel - [RFC][PATCH 10/18] x86/xen: Make get

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Message-ID: <20210621120121.210720354@infradead.org>
Date:   Mon, 21 Jun 2021 13:12:43 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     jpoimboe@...hat.com, tglx@...utronix.de
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        joro@...tes.org, boris.ostrovsky@...cle.com, jgross@...e.com,
        x86@...nel.org, mbenes@...e.com
Subject: [RFC][PATCH 10/18] x86/xen: Make get_debugreg() noinstr

vmlinux.o: warning: objtool: pv_ops[1]: xen_get_debugreg
vmlinux.o: warning: objtool: pv_ops[1]: native_get_debugreg
vmlinux.o: warning: objtool: exc_debug()+0x25: call to pv_ops[1]() leaves .noinstr.text section

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/include/asm/paravirt.h      |    2 +-
 arch/x86/include/asm/xen/hypercall.h |    2 +-
 arch/x86/kernel/paravirt.c           |    8 ++++++--
 arch/x86/xen/enlighten_pv.c          |    2 +-
 4 files changed, 9 insertions(+), 5 deletions(-)

--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -113,7 +113,7 @@ static inline void __cpuid(unsigned int
 /*
  * These special macros can be used to get or set a debugging register
  */
-static inline unsigned long paravirt_get_debugreg(int reg)
+static __always_inline unsigned long paravirt_get_debugreg(int reg)
 {
 	return PVOP_CALL1(unsigned long, cpu.get_debugreg, reg);
 }
--- a/arch/x86/include/asm/xen/hypercall.h
+++ b/arch/x86/include/asm/xen/hypercall.h
@@ -314,7 +314,7 @@ HYPERVISOR_set_debugreg(int reg, unsigne
 	return _hypercall2(int, set_debugreg, reg, value);
 }
 
-static inline unsigned long
+static __always_inline unsigned long
 HYPERVISOR_get_debugreg(int reg)
 {
 	return _hypercall1(unsigned long, get_debugreg, reg);
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -248,13 +248,18 @@ static noinstr void pv_native_write_cr2(
 	native_write_cr2(val);
 }
 
+static noinstr unsigned long pv_native_get_debugreg(int regno)
+{
+	return native_get_debugreg(regno);
+}
+
 struct paravirt_patch_template pv_ops = {
 	/* Cpu ops. */
 	.cpu.io_delay		= native_io_delay,
 
 #ifdef CONFIG_PARAVIRT_XXL
 	.cpu.cpuid		= native_cpuid,
-	.cpu.get_debugreg	= native_get_debugreg,
+	.cpu.get_debugreg	= pv_native_get_debugreg,
 	.cpu.set_debugreg	= native_set_debugreg,
 	.cpu.read_cr0		= native_read_cr0,
 	.cpu.write_cr0		= native_write_cr0,
@@ -382,7 +387,6 @@ struct paravirt_patch_template pv_ops =
 
 #ifdef CONFIG_PARAVIRT_XXL
 /* At this point, native_get/set_debugreg has real function entries */
-NOKPROBE_SYMBOL(native_get_debugreg);
 NOKPROBE_SYMBOL(native_set_debugreg);
 NOKPROBE_SYMBOL(native_load_idt);
 
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -317,7 +317,7 @@ static void xen_set_debugreg(int reg, un
 	HYPERVISOR_set_debugreg(reg, val);
 }
 
-static unsigned long xen_get_debugreg(int reg)
+static noinstr unsigned long xen_get_debugreg(int reg)
 {
 	return HYPERVISOR_get_debugreg(reg);
 }