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Subject[PATCH 4.4 094/107] x86/bugs: Remove x86_spec_ctrl_set()
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Thomas Gleixner <tglx@linutronix.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@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa@csail.mit.edu>
Reviewed-by: Matt Helsley (VMware) <matt.helsley@gmail.com>
Reviewed-by: Alexey Makhalov <amakhalov@vmware.com>
Reviewed-by: Bo Gan <ganb@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

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
@@ -131,15 +131,6 @@ 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)
{
@@ -501,7 +492,7 @@ 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();
@@ -613,7 +604,7 @@ 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();

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