arm64: cpufeature: Change DBM to display enabled cores

Now that we have the ability to display the list of cores
with a feature when its selectivly enabled, lets convert
DBM to use that as well.

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Link: https://lore.kernel.org/r/20231017052322.1211099-3-jeremy.linton@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 2dd695f..b7b67ba 100644 (file)
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1848,6 +1848,8 @@ static int __init parse_kpti(char *str)
 early_param("kpti", parse_kpti);
 
 #ifdef CONFIG_ARM64_HW_AFDBM
+static struct cpumask dbm_cpus __read_mostly;
+
 static inline void __cpu_enable_hw_dbm(void)
 {
        u64 tcr = read_sysreg(tcr_el1) | TCR_HD;
@@ -1883,35 +1885,22 @@ static bool cpu_can_use_dbm(const struct arm64_cpu_capabilities *cap)
 
 static void cpu_enable_hw_dbm(struct arm64_cpu_capabilities const *cap)
 {
-       if (cpu_can_use_dbm(cap))
+       if (cpu_can_use_dbm(cap)) {
                __cpu_enable_hw_dbm();
+               cpumask_set_cpu(smp_processor_id(), &dbm_cpus);
+       }
 }
 
 static bool has_hw_dbm(const struct arm64_cpu_capabilities *cap,
                       int __unused)
 {
-       static bool detected = false;
        /*
         * DBM is a non-conflicting feature. i.e, the kernel can safely
         * run a mix of CPUs with and without the feature. So, we
         * unconditionally enable the capability to allow any late CPU
         * to use the feature. We only enable the control bits on the
-        * CPU, if it actually supports.
-        *
-        * We have to make sure we print the "feature" detection only
-        * when at least one CPU actually uses it. So check if this CPU
-        * can actually use it and print the message exactly once.
-        *
-        * This is safe as all CPUs (including secondary CPUs - due to the
-        * LOCAL_CPU scope - and the hotplugged CPUs - via verification)
-        * goes through the "matches" check exactly once. Also if a CPU
-        * matches the criteria, it is guaranteed that the CPU will turn
-        * the DBM on, as the capability is unconditionally enabled.
+        * CPU, if it is supported.
         */
-       if (!detected && cpu_can_use_dbm(cap)) {
-               detected = true;
-               pr_info("detected: Hardware dirty bit management\n");
-       }
 
        return true;
 }
@@ -2448,18 +2437,12 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
        },
 #ifdef CONFIG_ARM64_HW_AFDBM
        {
-               /*
-                * Since we turn this on always, we don't want the user to
-                * think that the feature is available when it may not be.
-                * So hide the description.
-                *
-                * .desc = "Hardware pagetable Dirty Bit Management",
-                *
-                */
+               .desc = "Hardware dirty bit management",
                .type = ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE,
                .capability = ARM64_HW_DBM,
                .matches = has_hw_dbm,
                .cpu_enable = cpu_enable_hw_dbm,
+               .cpus = &dbm_cpus,
                ARM64_CPUID_FIELDS(ID_AA64MMFR1_EL1, HAFDBS, DBM)
        },
 #endif