[RFC PATCH v2 2/3] KVM: arm64: Use hypercall to retrieve any migration targets

[Shameer Kolothum]

Provides a paravirt helper function to retrieve any migration target
CPUs if available and store it. This will be used in subsequent patch
to enable any errata associated with those targets

Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi at huawei.com>
---
ToDo:
Not sure it make sense to use kvm_arm_hyp_service_available() here
as these hypercalls will be handled by userspace VMM.

---
 arch/arm64/include/asm/cpufeature.h |  7 +++++
 arch/arm64/include/asm/paravirt.h   |  3 ++
 arch/arm64/kernel/cpu_errata.c      |  3 ++
 arch/arm64/kernel/paravirt.c        | 48 +++++++++++++++++++++++++++++
 4 files changed, 61 insertions(+)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 985d966787b1..6623f47814bc 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -386,6 +386,13 @@ struct arm64_cpu_capabilities {
 	const struct cpumask *cpus;
 };
 
+#define MIGRN_TARGET_CPUS_HYP_CALL_VER_1	1
+#define MAX_MIGRN_TARGET_CPUS			64
+struct migrn_target {
+	u32 midr;
+	u32 revidr;
+};
+
 static inline int cpucap_default_scope(const struct arm64_cpu_capabilities *cap)
 {
 	return cap->type & ARM64_CPUCAP_SCOPE_MASK;
diff --git a/arch/arm64/include/asm/paravirt.h b/arch/arm64/include/asm/paravirt.h
index 9aa193e0e8f2..19cd97dafbbc 100644
--- a/arch/arm64/include/asm/paravirt.h
+++ b/arch/arm64/include/asm/paravirt.h
@@ -19,11 +19,14 @@ static inline u64 paravirt_steal_clock(int cpu)
 }
 
 int __init pv_time_init(void);
+void __init pv_errata_migrn_target_init(void);
 
 #else
 
 #define pv_time_init() do {} while (0)
 
+#define pv_errata_migrn_target_init() do {} while (0)
+
 #endif // CONFIG_PARAVIRT
 
 #endif
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index dfefbdf4073a..feaaf2b11f46 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -14,6 +14,9 @@
 #include <asm/kvm_asm.h>
 #include <asm/smp_plat.h>
 
+u32 __ro_after_init errata_migrn_target_num;
+struct migrn_target __ro_after_init errata_migrn_target_cpus[MAX_MIGRN_TARGET_CPUS];
+
 static bool __maybe_unused
 is_affected_midr_range(const struct arm64_cpu_capabilities *entry, int scope)
 {
diff --git a/arch/arm64/kernel/paravirt.c b/arch/arm64/kernel/paravirt.c
index aa718d6a9274..675424258419 100644
--- a/arch/arm64/kernel/paravirt.c
+++ b/arch/arm64/kernel/paravirt.c
@@ -153,6 +153,54 @@ static bool __init has_pv_steal_clock(void)
 	return (res.a0 == SMCCC_RET_SUCCESS);
 }
 
+extern struct migrn_target __ro_after_init errata_migrn_target_cpus[];
+extern u32 __ro_after_init errata_migrn_target_num;
+void  __init pv_errata_migrn_target_init(void)
+{
+	u32 target_num;
+	struct arm_smccc_res res;
+	u32 curr = 0;
+
+	/* Check we have already set errata targets */
+	if (errata_migrn_target_num)
+		return;
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_MIGRN_TARGET_NUM_FUNC_ID, &res);
+	if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
+		return;
+
+	target_num = lower_32_bits(res.a0);
+	if (!target_num || target_num > MAX_MIGRN_TARGET_CPUS ||
+	    upper_32_bits(res.a0) != MIGRN_TARGET_CPUS_HYP_CALL_VER_1)
+		return;
+
+	while (curr < target_num) {
+		unsigned long *ptr;
+		int j;
+
+		arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_MIGRN_TARGET_CPUS_FUNC_ID, &res);
+		if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
+			break;
+
+		ptr = (unsigned long *)&res;
+		for (j = 0; j < 4; j++, ptr++) {
+			if (!(*ptr))
+				goto out;
+			errata_migrn_target_cpus[curr].midr = lower_32_bits(*ptr);
+			errata_migrn_target_cpus[curr].revidr = upper_32_bits(*ptr);
+			curr++;
+		}
+	}
+out:
+	if (curr != target_num) {
+		pr_warn("Failed to retrieve all migration target CPUs\n");
+		return;
+	}
+
+	errata_migrn_target_num = target_num;
+	pr_info("Migration target CPUs set to %d\n", target_num);
+}
+
 int __init pv_time_init(void)
 {
 	int ret;
-- 
2.45.2