[PATCH 1/6] arm64: kpti: move check for non-vulnerable CPUs to a function

[Jeremy Linton]

From: Mian Yousaf Kaukab <ykau...@suse.de>

Add is_meltdown_safe() which is a whitelist of known safe cores.

Signed-off-by: Mian Yousaf Kaukab <ykau...@suse.de>
[Moved location of function]
Signed-off-by: Jeremy Linton <jeremy.lin...@arm.com>
---
 arch/arm64/kernel/cpufeature.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index aec5ecb85737..242898395f68 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -908,8 +908,7 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, 
int scope)
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
 static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */
 
-static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
-                               int scope)
+static bool is_cpu_meltdown_safe(void)
 {
        /* List of CPUs that are not vulnerable and don't need KPTI */
        static const struct midr_range kpti_safe_list[] = {
@@ -917,6 +916,16 @@ static bool unmap_kernel_at_el0(const struct 
arm64_cpu_capabilities *entry,
                MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
                { /* sentinel */ }
        };
+       /* Don't force KPTI for CPUs that are not vulnerable */
+       if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list))
+               return true;
+
+       return false;
+}
+
+static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
+                               int scope)
+{
        char const *str = "command line option";
 
        /*
@@ -940,8 +949,7 @@ static bool unmap_kernel_at_el0(const struct 
arm64_cpu_capabilities *entry,
        if (IS_ENABLED(CONFIG_RANDOMIZE_BASE))
                return true;
 
-       /* Don't force KPTI for CPUs that are not vulnerable */
-       if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list))
+       if (is_cpu_meltdown_safe())
                return false;
 
        /* Defer to CPU feature registers */
-- 
2.17.2