[PATCH 4.9 07/31] x86/cpu: Add a helper function x86_read_arch_cap_msr()

Greg Kroah-Hartman
2019-11-15T06:23:32Z

From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>

commit 286836a70433fb64131d2590f4bf512097c255e1 upstream.

Add a helper function to read the IA32_ARCH_CAPABILITIES MSR.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Neelima Krishnan <neelima.krishnan@intel.com>
Reviewed-by: Mark Gross <mgross@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kernel/cpu/common.c | 15 +++++++++++----
arch/x86/kernel/cpu/cpu.h | 2 ++
2 files changed, 13 insertions(+), 4 deletions(-)

--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -962,19 +962,26 @@ static bool __init cpu_matches(unsigned
return m && !!(m->driver_data & which);
}

-static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
+u64 x86_read_arch_cap_msr(void)
{
u64 ia32_cap = 0;

+ if (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES))
+ rdmsrl(MSR_IA32_ARCH_CAPABILITIES, ia32_cap);
+
+ return ia32_cap;
+}
+
+static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
+{
+ u64 ia32_cap = x86_read_arch_cap_msr();
+
if (cpu_matches(NO_SPECULATION))
return;

setup_force_cpu_bug(X86_BUG_SPECTRE_V1);
setup_force_cpu_bug(X86_BUG_SPECTRE_V2);

- if (cpu_has(c, X86_FEATURE_ARCH_CAPABILITIES))
- rdmsrl(MSR_IA32_ARCH_CAPABILITIES, ia32_cap);
-
if (!cpu_matches(NO_SSB) && !(ia32_cap & ARCH_CAP_SSB_NO) &&
!cpu_has(c, X86_FEATURE_AMD_SSB_NO))
setup_force_cpu_bug(X86_BUG_SPEC_STORE_BYPASS);
--- a/arch/x86/kernel/cpu/cpu.h
+++ b/arch/x86/kernel/cpu/cpu.h
@@ -51,4 +51,6 @@ extern int detect_ht_early(struct cpuinf

extern void x86_spec_ctrl_setup_ap(void);

+extern u64 x86_read_arch_cap_msr(void);
+
#endif /* ARCH_X86_CPU_H */