linux-kernel - [PATCH 3.16 043/131] x86/bugs: Remove x86_spec_ctrl

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Message-ID: <lsq.1538257387.801346577@decadent.org.uk>
Date:   Sat, 29 Sep 2018 22:43:07 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "David Woodhouse" <dwmw@...zon.co.uk>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Borislav Petkov" <bp@...e.de>,
        "Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>
Subject: [PATCH 3.16 043/131] x86/bugs: Remove x86_spec_ctrl_set()

3.16.59-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@...utronix.de>

commit 4b59bdb569453a60b752b274ca61f009e37f4dae upstream.

x86_spec_ctrl_set() is only used in bugs.c and the extra mask checks there
provide no real value as both call sites can just write x86_spec_ctrl_base
to MSR_SPEC_CTRL. x86_spec_ctrl_base is valid and does not need any extra
masking or checking.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/include/asm/nospec-branch.h |  2 --
 arch/x86/kernel/cpu/bugs.c           | 13 ++-----------
 2 files changed, 2 insertions(+), 13 deletions(-)

--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -172,8 +172,6 @@ enum spectre_v2_mitigation {
 	SPECTRE_V2_IBRS,
 };
 
-extern void x86_spec_ctrl_set(u64);
-
 /* The Speculative Store Bypass disable variants */
 enum ssb_mitigation {
 	SPEC_STORE_BYPASS_NONE,
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -194,15 +194,6 @@ static const char *spectre_v2_strings[]
 
 static enum spectre_v2_mitigation spectre_v2_enabled = SPECTRE_V2_NONE;
 
-void x86_spec_ctrl_set(u64 val)
-{
-	if (val & x86_spec_ctrl_mask)
-		WARN_ONCE(1, "SPEC_CTRL MSR value 0x%16llx is unknown.\n", val);
-	else
-		wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base | val);
-}
-EXPORT_SYMBOL_GPL(x86_spec_ctrl_set);
-
 void
 x86_virt_spec_ctrl(u64 guest_spec_ctrl, u64 guest_virt_spec_ctrl, bool setguest)
 {
@@ -540,7 +531,7 @@ static enum ssb_mitigation __init __ssb_
 		case X86_VENDOR_INTEL:
 			x86_spec_ctrl_base |= SPEC_CTRL_SSBD;
 			x86_spec_ctrl_mask &= ~SPEC_CTRL_SSBD;
-			x86_spec_ctrl_set(SPEC_CTRL_SSBD);
+			wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
 			break;
 		case X86_VENDOR_AMD:
 			x86_amd_ssb_disable();
@@ -652,7 +643,7 @@ int arch_prctl_spec_ctrl_get(struct task
 void x86_spec_ctrl_setup_ap(void)
 {
 	if (boot_cpu_has(X86_FEATURE_MSR_SPEC_CTRL))
-		x86_spec_ctrl_set(x86_spec_ctrl_base & ~x86_spec_ctrl_mask);
+		wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
 
 	if (ssb_mode == SPEC_STORE_BYPASS_DISABLE)
 		x86_amd_ssb_disable();