1 files changed, 165 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/paravirt.h b/arch/powerpc/include/asm/paravirt.h
new file mode 100644
index 000000000..e08513d73
--- /dev/null
+++ b/arch/powerpc/include/asm/paravirt.h
@@ -0,0 +1,165 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _ASM_POWERPC_PARAVIRT_H
+#define _ASM_POWERPC_PARAVIRT_H
+
+#include <linux/jump_label.h>
+#include <asm/smp.h>
+#ifdef CONFIG_PPC64
+#include <asm/paca.h>
+#include <asm/lppaca.h>
+#include <asm/hvcall.h>
+#endif
+
+#ifdef CONFIG_PPC_SPLPAR
+#include <linux/smp.h>
+#include <asm/kvm_guest.h>
+#include <asm/cputhreads.h>
+
+DECLARE_STATIC_KEY_FALSE(shared_processor);
+
+static inline bool is_shared_processor(void)
+{
+	return static_branch_unlikely(&shared_processor);
+}
+
+#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
+extern struct static_key paravirt_steal_enabled;
+extern struct static_key paravirt_steal_rq_enabled;
+
+u64 pseries_paravirt_steal_clock(int cpu);
+
+static inline u64 paravirt_steal_clock(int cpu)
+{
+	return pseries_paravirt_steal_clock(cpu);
+}
+#endif
+
+/* If bit 0 is set, the cpu has been ceded, conferred, or preempted */
+static inline u32 yield_count_of(int cpu)
+{
+	__be32 yield_count = READ_ONCE(lppaca_of(cpu).yield_count);
+	return be32_to_cpu(yield_count);
+}
+
+/*
+ * Spinlock code confers and prods, so don't trace the hcalls because the
+ * tracing code takes spinlocks which can cause recursion deadlocks.
+ *
+ * These calls are made while the lock is not held: the lock slowpath yields if
+ * it can not acquire the lock, and unlock slow path might prod if a waiter has
+ * yielded). So this may not be a problem for simple spin locks because the
+ * tracing does not technically recurse on the lock, but we avoid it anyway.
+ *
+ * However the queued spin lock contended path is more strictly ordered: the
+ * H_CONFER hcall is made after the task has queued itself on the lock, so then
+ * recursing on that lock will cause the task to then queue up again behind the
+ * first instance (or worse: queued spinlocks use tricks that assume a context
+ * never waits on more than one spinlock, so such recursion may cause random
+ * corruption in the lock code).
+ */
+static inline void yield_to_preempted(int cpu, u32 yield_count)
+{
+	plpar_hcall_norets_notrace(H_CONFER, get_hard_smp_processor_id(cpu), yield_count);
+}
+
+static inline void prod_cpu(int cpu)
+{
+	plpar_hcall_norets_notrace(H_PROD, get_hard_smp_processor_id(cpu));
+}
+
+static inline void yield_to_any(void)
+{
+	plpar_hcall_norets_notrace(H_CONFER, -1, 0);
+}
+#else
+static inline bool is_shared_processor(void)
+{
+	return false;
+}
+
+static inline u32 yield_count_of(int cpu)
+{
+	return 0;
+}
+
+extern void ___bad_yield_to_preempted(void);
+static inline void yield_to_preempted(int cpu, u32 yield_count)
+{
+	___bad_yield_to_preempted(); /* This would be a bug */
+}
+
+extern void ___bad_yield_to_any(void);
+static inline void yield_to_any(void)
+{
+	___bad_yield_to_any(); /* This would be a bug */
+}
+
+extern void ___bad_prod_cpu(void);
+static inline void prod_cpu(int cpu)
+{
+	___bad_prod_cpu(); /* This would be a bug */
+}
+
+#endif
+
+#define vcpu_is_preempted vcpu_is_preempted
+static inline bool vcpu_is_preempted(int cpu)
+{
+	/*
+	 * The dispatch/yield bit alone is an imperfect indicator of
+	 * whether the hypervisor has dispatched @cpu to run on a physical
+	 * processor. When it is clear, @cpu is definitely not preempted.
+	 * But when it is set, it means only that it *might* be, subject to
+	 * other conditions. So we check other properties of the VM and
+	 * @cpu first, resorting to the yield count last.
+	 */
+
+	/*
+	 * Hypervisor preemption isn't possible in dedicated processor
+	 * mode by definition.
+	 */
+	if (!is_shared_processor())
+		return false;
+
+#ifdef CONFIG_PPC_SPLPAR
+	if (!is_kvm_guest()) {
+		int first_cpu;
+
+		/*
+		 * The result of vcpu_is_preempted() is used in a
+		 * speculative way, and is always subject to invalidation
+		 * by events internal and external to Linux. While we can
+		 * be called in preemptable context (in the Linux sense),
+		 * we're not accessing per-cpu resources in a way that can
+		 * race destructively with Linux scheduler preemption and
+		 * migration, and callers can tolerate the potential for
+		 * error introduced by sampling the CPU index without
+		 * pinning the task to it. So it is permissible to use
+		 * raw_smp_processor_id() here to defeat the preempt debug
+		 * warnings that can arise from using smp_processor_id()
+		 * in arbitrary contexts.
+		 */
+		first_cpu = cpu_first_thread_sibling(raw_smp_processor_id());
+
+		/*
+		 * The PowerVM hypervisor dispatches VMs on a whole core
+		 * basis. So we know that a thread sibling of the local CPU
+		 * cannot have been preempted by the hypervisor, even if it
+		 * has called H_CONFER, which will set the yield bit.
+		 */
+		if (cpu_first_thread_sibling(cpu) == first_cpu)
+			return false;
+	}
+#endif
+
+	if (yield_count_of(cpu) & 1)
+		return true;
+	return false;
+}
+
+static inline bool pv_is_native_spin_unlock(void)
+{
+	return !is_shared_processor();
+}
+
+#endif /* _ASM_POWERPC_PARAVIRT_H */