x86/bugs: Remove x86_spec_ctrl_set()

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>
CVE-2018-3639 (x86)

(cherry-picked from commit 4b59bdb569453a60b752b274ca61f009e37f4dae)
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index ef2d6a087ac08621a4aab8846b2fb708354777b9..d219cc6f89e5112eb2fb3185cd41ef107d82fbe1 100644 (file)
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -165,8 +165,6 @@ 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,

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 3834479e6d56ed5bf117f943f532ca674ca8aad5..2c7206fdc09e4f3200405429d635066624fcfe28 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -132,15 +132,6 @@ static const char *spectre_v2_strings[] = {
 static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
        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)
 {
@@ -462,7 +453,7 @@ static enum ssb_mitigation __init __ssb_select_mitigation(void)
                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();
@@ -574,7 +565,7 @@ int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
 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();