linux-kernel - [RFC][PATCH 09/18] x86/xen: Make write

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Message-ID: <20210621120121.127655715@infradead.org>
Date:   Mon, 21 Jun 2021 13:12:42 +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 09/18] x86/xen: Make write_cr2() noinstr

vmlinux.o: warning: objtool: pv_ops[42]: native_write_cr2
vmlinux.o: warning: objtool: pv_ops[42]: xen_write_cr2
vmlinux.o: warning: objtool: exc_nmi()+0x127: call to pv_ops[42]() leaves .noinstr.text section

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/include/asm/paravirt.h |    2 +-
 arch/x86/kernel/paravirt.c      |    7 ++++++-
 arch/x86/xen/mmu_pv.c           |    3 ++-
 3 files changed, 9 insertions(+), 3 deletions(-)

--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -140,7 +140,7 @@ static __always_inline unsigned long rea
 				ALT_NOT(X86_FEATURE_XENPV));
 }
 
-static inline void write_cr2(unsigned long x)
+static __always_inline void write_cr2(unsigned long x)
 {
 	PVOP_VCALL1(mmu.write_cr2, x);
 }
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -243,6 +243,11 @@ static noinstr unsigned long pv_native_r
 	return native_read_cr2();
 }
 
+static noinstr void pv_native_write_cr2(unsigned long val)
+{
+	native_write_cr2(val);
+}
+
 struct paravirt_patch_template pv_ops = {
 	/* Cpu ops. */
 	.cpu.io_delay		= native_io_delay,
@@ -304,7 +309,7 @@ struct paravirt_patch_template pv_ops =
 
 #ifdef CONFIG_PARAVIRT_XXL
 	.mmu.read_cr2		= __PV_IS_CALLEE_SAVE(pv_native_read_cr2),
-	.mmu.write_cr2		= native_write_cr2,
+	.mmu.write_cr2		= pv_native_write_cr2,
 	.mmu.read_cr3		= __native_read_cr3,
 	.mmu.write_cr3		= native_write_cr3,
 
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -1204,7 +1204,8 @@ static void __init xen_pagetable_init(vo
 	xen_remap_memory();
 	xen_setup_mfn_list_list();
 }
-static void xen_write_cr2(unsigned long cr2)
+
+static noinstr void xen_write_cr2(unsigned long cr2)
 {
 	this_cpu_read(xen_vcpu)->arch.cr2 = cr2;
 }