[PATCH 4/4] powerpc/pseries: Implement CONFIG_PARAVIRT_TIME_ACCOUNTING

[Nicholas Piggin <npiggin@gmail.com>]

CONFIG_VIRT_CPU_ACCOUNTING_GEN under pseries does not implement
stolen time accounting. Implement it with the paravirt time
accounting option.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 .../admin-guide/kernel-parameters.txt         |  6 +++---
 arch/powerpc/include/asm/paravirt.h           | 12 ++++++++++++
 arch/powerpc/platforms/pseries/Kconfig        |  8 ++++++++
 arch/powerpc/platforms/pseries/lpar.c         | 11 +++++++++++
 arch/powerpc/platforms/pseries/setup.c        | 19 +++++++++++++++++++
 5 files changed, 53 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 3f1cc5e317ed..855fc7b02261 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3604,9 +3604,9 @@
 			[X86,PV_OPS] Disable paravirtualized VMware scheduler
 			clock and use the default one.
 
-	no-steal-acc	[X86,PV_OPS,ARM64] Disable paravirtualized steal time
-			accounting. steal time is computed, but won't
-			influence scheduler behaviour
+	no-steal-acc	[X86,PV_OPS,ARM64,PPC/PSERIES] Disable paravirtualized
+			steal time accounting. steal time is computed, but
+			won't influence scheduler behaviour
 
 	nolapic		[X86-32,APIC] Do not enable or use the local APIC.
 
diff --git a/arch/powerpc/include/asm/paravirt.h b/arch/powerpc/include/asm/paravirt.h
index eb7df559ae74..f5ba1a3c41f8 100644
--- a/arch/powerpc/include/asm/paravirt.h
+++ b/arch/powerpc/include/asm/paravirt.h
@@ -21,6 +21,18 @@ 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)
 {
diff --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platforms/pseries/Kconfig
index f7fd91d153a4..d4306ebdca5e 100644
--- a/arch/powerpc/platforms/pseries/Kconfig
+++ b/arch/powerpc/platforms/pseries/Kconfig
@@ -24,13 +24,21 @@ config PPC_PSERIES
 	select SWIOTLB
 	default y
 
+config PARAVIRT
+	bool
+
 config PARAVIRT_SPINLOCKS
 	bool
 
+config PARAVIRT_TIME_ACCOUNTING
+	select PARAVIRT
+	bool
+
 config PPC_SPLPAR
 	bool "Support for shared-processor logical partitions"
 	depends on PPC_PSERIES
 	select PARAVIRT_SPINLOCKS if PPC_QUEUED_SPINLOCKS
+	select PARAVIRT_TIME_ACCOUNTING if VIRT_CPU_ACCOUNTING_GEN
 	default y
 	help
 	  Enabling this option will make the kernel run more efficiently
diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
index 760581c5752f..1965b7d7d8f1 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -661,6 +661,17 @@ static int __init vcpudispatch_stats_procfs_init(void)
 }
 
 machine_device_initcall(pseries, vcpudispatch_stats_procfs_init);
+
+#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
+u64 pseries_paravirt_steal_clock(int cpu)
+{
+	struct lppaca *lppaca = &lppaca_of(cpu);
+
+	return be64_to_cpu(READ_ONCE(lppaca->enqueue_dispatch_tb)) +
+		be64_to_cpu(READ_ONCE(lppaca->ready_enqueue_tb));
+}
+#endif
+
 #endif /* CONFIG_PPC_SPLPAR */
 
 void vpa_init(int cpu)
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 955ff8aa1644..691c9add4a5a 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -78,6 +78,20 @@
 DEFINE_STATIC_KEY_FALSE(shared_processor);
 EXPORT_SYMBOL(shared_processor);
 
+#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
+struct static_key paravirt_steal_enabled;
+struct static_key paravirt_steal_rq_enabled;
+
+static bool steal_acc = true;
+static int __init parse_no_stealacc(char *arg)
+{
+	steal_acc = false;
+	return 0;
+}
+
+early_param("no-steal-acc", parse_no_stealacc);
+#endif
+
 int CMO_PrPSP = -1;
 int CMO_SecPSP = -1;
 unsigned long CMO_PageSize = (ASM_CONST(1) << IOMMU_PAGE_SHIFT_4K);
@@ -831,6 +845,11 @@ static void __init pSeries_setup_arch(void)
 		if (lppaca_shared_proc(get_lppaca())) {
 			static_branch_enable(&shared_processor);
 			pv_spinlocks_init();
+#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
+			static_key_slow_inc(&paravirt_steal_enabled);
+			if (steal_acc)
+				static_key_slow_inc(&paravirt_steal_rq_enabled);
+#endif
 		}
 
 		ppc_md.power_save = pseries_lpar_idle;
-- 
2.35.1