[PATCH 0/5] doorbell patches for POWER9

[PATCH 0/5] doorbell patches for POWER9

[Nicholas Piggin]

This is what I'd like to do for POWER9 doorbells, which reworks
the existing code a bit. I guess it won't work on DD1 with OPAL
until darn is fixed (only tested on POWER9 using mambo).

Nicholas Piggin (5):
  powerpc/pseries: do not use msgsndp doorbells on POWER9 guests
  powerpc: change the doorbell IPI calling convention
  powerpc: Introduce msgsnd/doorbell barrier primitives
  powerpc/64s: avoid branch for ppc_msgsnd
  powerpc/powernv: POWER9 support for msgsnd/doorbell IPI

 arch/powerpc/include/asm/dbell.h          | 45 ++++++++++++++++++------
 arch/powerpc/include/asm/feature-fixups.h | 20 +++++++++++
 arch/powerpc/include/asm/ppc-opcode.h     |  6 ++++
 arch/powerpc/include/asm/ppc_asm.h        | 15 ++++++++
 arch/powerpc/include/asm/smp.h            |  4 +--
 arch/powerpc/include/asm/xics.h           |  2 +-
 arch/powerpc/kernel/dbell.c               | 58 +++++++++++++++++++++++++++----
 arch/powerpc/kernel/smp.c                 | 27 +++++++-------
 arch/powerpc/platforms/85xx/smp.c         | 11 ++----
 arch/powerpc/platforms/powermac/smp.c     |  2 +-
 arch/powerpc/platforms/powernv/smp.c      | 33 +++++++++++++-----
 arch/powerpc/platforms/pseries/smp.c      | 33 ++++++++----------
 arch/powerpc/sysdev/xics/icp-hv.c         |  2 +-
 arch/powerpc/sysdev/xics/icp-native.c     | 12 +------
 arch/powerpc/sysdev/xics/icp-opal.c       |  2 +-
 arch/powerpc/sysdev/xics/xics-common.c    |  3 --
 16 files changed, 189 insertions(+), 86 deletions(-)

-- 
2.11.0

[PATCH 1/5] powerpc/pseries: do not use msgsndp doorbells on POWER9 guests

[Nicholas Piggin]

POWER9 hypervisors will not necessarily run guest threads together on
the same core at the same time, so msgsndp should not be used.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/platforms/pseries/smp.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c
index f6f83aeccaaa..1fa08155206b 100644
--- a/arch/powerpc/platforms/pseries/smp.c
+++ b/arch/powerpc/platforms/pseries/smp.c
@@ -200,7 +200,12 @@ static __init void pSeries_smp_probe(void)
 {
 	xics_smp_probe();
 
-	if (cpu_has_feature(CPU_FTR_DBELL)) {
+	/*
+	 * POWER9 can not use msgsndp doorbells for IPI because thread
+	 * siblings do not necessarily run on physical cores at the same
+	 * time. This could be enabled for pHyp.
+	 */
+	if (cpu_has_feature(CPU_FTR_DBELL) && !cpu_has_feature(CPU_FTR_ARCH_300)) {
 		xics_cause_ipi = smp_ops->cause_ipi;
 		smp_ops->cause_ipi = pSeries_cause_ipi_mux;
 	}
-- 
2.11.0

[PATCH 2/5] powerpc: change the doorbell IPI calling convention

[Nicholas Piggin]

Change the doorbell callers to know about their msgsnd addressing, rather
than have them set a per-cpu target data tag at boot that gets sent to the
cause_ipi functions. The data is only used for doorbell IPI functions, no
other IPI types, so it makes sense to keep that detail local to doorbell.

Have the platform code understand doorbell IPIs, rather than the interrupt
controller code understand them. Platform code can look at capabilities
it has available and decide which to use.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/include/asm/dbell.h       |  9 ++----
 arch/powerpc/include/asm/smp.h         |  3 +-
 arch/powerpc/include/asm/xics.h        |  2 +-
 arch/powerpc/kernel/dbell.c            | 52 ++++++++++++++++++++++++++++++----
 arch/powerpc/kernel/smp.c              | 17 ++++-------
 arch/powerpc/platforms/85xx/smp.c      | 11 ++-----
 arch/powerpc/platforms/powermac/smp.c  |  2 +-
 arch/powerpc/platforms/powernv/smp.c   | 29 +++++++++++++------
 arch/powerpc/platforms/pseries/smp.c   | 28 +++++++-----------
 arch/powerpc/sysdev/xics/icp-hv.c      |  2 +-
 arch/powerpc/sysdev/xics/icp-native.c  | 12 +-------
 arch/powerpc/sysdev/xics/icp-opal.c    |  2 +-
 arch/powerpc/sysdev/xics/xics-common.c |  3 --
 13 files changed, 94 insertions(+), 78 deletions(-)

diff --git a/arch/powerpc/include/asm/dbell.h b/arch/powerpc/include/asm/dbell.h
index 378167377065..5a7301f333a4 100644
--- a/arch/powerpc/include/asm/dbell.h
+++ b/arch/powerpc/include/asm/dbell.h
@@ -35,8 +35,6 @@ enum ppc_dbell {
 #ifdef CONFIG_PPC_BOOK3S
 
 #define PPC_DBELL_MSGTYPE		PPC_DBELL_SERVER
-#define SPRN_DOORBELL_CPUTAG		SPRN_TIR
-#define PPC_DBELL_TAG_MASK		0x7f
 
 static inline void _ppc_msgsnd(u32 msg)
 {
@@ -49,8 +47,6 @@ static inline void _ppc_msgsnd(u32 msg)
 #else /* CONFIG_PPC_BOOK3S */
 
 #define PPC_DBELL_MSGTYPE		PPC_DBELL
-#define SPRN_DOORBELL_CPUTAG		SPRN_PIR
-#define PPC_DBELL_TAG_MASK		0x3fff
 
 static inline void _ppc_msgsnd(u32 msg)
 {
@@ -59,9 +55,10 @@ static inline void _ppc_msgsnd(u32 msg)
 
 #endif /* CONFIG_PPC_BOOK3S */
 
-extern void doorbell_cause_ipi(int cpu, unsigned long data);
+extern void global_doorbell_cause_ipi(int cpu);
+extern void core_doorbell_cause_ipi(int cpu);
+extern int try_core_doorbell_cause_ipi(int cpu);
 extern void doorbell_exception(struct pt_regs *regs);
-extern void doorbell_setup_this_cpu(void);
 
 static inline void ppc_msgsnd(enum ppc_dbell type, u32 flags, u32 tag)
 {
diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
index 32db16d2e7ad..0ada12e61fd7 100644
--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h
@@ -40,7 +40,7 @@ extern int cpu_to_chip_id(int cpu);
 struct smp_ops_t {
 	void  (*message_pass)(int cpu, int msg);
 #ifdef CONFIG_PPC_SMP_MUXED_IPI
-	void  (*cause_ipi)(int cpu, unsigned long data);
+	void  (*cause_ipi)(int cpu);
 #endif
 	void  (*probe)(void);
 	int   (*kick_cpu)(int nr);
@@ -125,7 +125,6 @@ extern int smp_request_message_ipi(int virq, int message);
 extern const char *smp_ipi_name[];
 
 /* for irq controllers with only a single ipi */
-extern void smp_muxed_ipi_set_data(int cpu, unsigned long data);
 extern void smp_muxed_ipi_message_pass(int cpu, int msg);
 extern void smp_muxed_ipi_set_message(int cpu, int msg);
 extern irqreturn_t smp_ipi_demux(void);
diff --git a/arch/powerpc/include/asm/xics.h b/arch/powerpc/include/asm/xics.h
index e0b9e576905a..7ce2c3ac2964 100644
--- a/arch/powerpc/include/asm/xics.h
+++ b/arch/powerpc/include/asm/xics.h
@@ -57,7 +57,7 @@ struct icp_ops {
 	void (*teardown_cpu)(void);
 	void (*flush_ipi)(void);
 #ifdef CONFIG_SMP
-	void (*cause_ipi)(int cpu, unsigned long data);
+	void (*cause_ipi)(int cpu);
 	irq_handler_t ipi_action;
 #endif
 };
diff --git a/arch/powerpc/kernel/dbell.c b/arch/powerpc/kernel/dbell.c
index 2128f3a96c32..2b41f145de05 100644
--- a/arch/powerpc/kernel/dbell.c
+++ b/arch/powerpc/kernel/dbell.c
@@ -20,18 +20,60 @@
 #include <asm/kvm_ppc.h>
 
 #ifdef CONFIG_SMP
-void doorbell_setup_this_cpu(void)
+
+/*
+ * Doorbells must only be used if CPU_FTR_DBELL is available.
+ * msgsnd is used in HV, and msgsndp is used in !HV.
+ *
+ * These should be used by platform code that is aware of restrictions.
+ * Other arch code should use ->cause_ipi.
+ *
+ * global_doorbell_cause_ipi sends a dbell to any target CPU.
+ * Must be used only by architectures that address msgsnd target
+ * by PIR/get_hard_smp_processor_id.
+ */
+void global_doorbell_cause_ipi(int cpu)
 {
-	unsigned long tag = mfspr(SPRN_DOORBELL_CPUTAG) & PPC_DBELL_TAG_MASK;
+	u32 tag = get_hard_smp_processor_id(cpu);
 
-	smp_muxed_ipi_set_data(smp_processor_id(), tag);
+	kvmppc_set_host_ipi(cpu, 1);
+	/* Order previous accesses vs. msgsnd, which is treated as a store */
+	mb();
+	ppc_msgsnd(PPC_DBELL_MSGTYPE, 0, tag);
 }
 
-void doorbell_cause_ipi(int cpu, unsigned long data)
+/*
+ * core_doorbell_cause_ipi sends a dbell to the target CPU.
+ * Must be used only by architectures that address msgsnd target
+ * by TIR/cpu_thread_in_core.
+ */
+void core_doorbell_cause_ipi(int cpu)
 {
+	u32 tag = cpu_thread_in_core(cpu);
+
+	kvmppc_set_host_ipi(cpu, 1);
 	/* Order previous accesses vs. msgsnd, which is treated as a store */
 	mb();
-	ppc_msgsnd(PPC_DBELL_MSGTYPE, 0, data);
+	ppc_msgsnd(PPC_DBELL_MSGTYPE, 0, tag);
+}
+
+/*
+ * Attempt to cause a core doorbell if destination is on the same core.
+ * Returns 1 on success, 0 on failure.
+ */
+int try_core_doorbell_cause_ipi(int cpu)
+{
+	int this_cpu = get_cpu();
+	int ret = 0;
+
+	if (cpumask_test_cpu(cpu, cpu_sibling_mask(this_cpu))) {
+		core_doorbell_cause_ipi(cpu);
+		ret = 1;
+	}
+
+	put_cpu();
+
+	return ret;
 }
 
 void doorbell_exception(struct pt_regs *regs)
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 46f89e66a273..f1f6e4e3906b 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -39,6 +39,7 @@
 #include <asm/irq.h>
 #include <asm/hw_irq.h>
 #include <asm/kvm_ppc.h>
+#include <asm/dbell.h>
 #include <asm/page.h>
 #include <asm/pgtable.h>
 #include <asm/prom.h>
@@ -211,17 +212,9 @@ int smp_request_message_ipi(int virq, int msg)
 #ifdef CONFIG_PPC_SMP_MUXED_IPI
 struct cpu_messages {
 	long messages;			/* current messages */
-	unsigned long data;		/* data for cause ipi */
 };
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct cpu_messages, ipi_message);
 
-void smp_muxed_ipi_set_data(int cpu, unsigned long data)
-{
-	struct cpu_messages *info = &per_cpu(ipi_message, cpu);
-
-	info->data = data;
-}
-
 void smp_muxed_ipi_set_message(int cpu, int msg)
 {
 	struct cpu_messages *info = &per_cpu(ipi_message, cpu);
@@ -236,14 +229,13 @@ void smp_muxed_ipi_set_message(int cpu, int msg)
 
 void smp_muxed_ipi_message_pass(int cpu, int msg)
 {
-	struct cpu_messages *info = &per_cpu(ipi_message, cpu);
-
 	smp_muxed_ipi_set_message(cpu, msg);
+
 	/*
 	 * cause_ipi functions are required to include a full barrier
 	 * before doing whatever causes the IPI.
 	 */
-	smp_ops->cause_ipi(cpu, info->data);
+	smp_ops->cause_ipi(cpu);
 }
 
 #ifdef __BIG_ENDIAN__
@@ -254,11 +246,12 @@ void smp_muxed_ipi_message_pass(int cpu, int msg)
 
 irqreturn_t smp_ipi_demux(void)
 {
-	struct cpu_messages *info = this_cpu_ptr(&ipi_message);
+	struct cpu_messages *info;
 	unsigned long all;
 
 	mb();	/* order any irq clear */
 
+	info = this_cpu_ptr(&ipi_message);
 	do {
 		all = xchg(&info->messages, 0);
 #if defined(CONFIG_KVM_XICS) && defined(CONFIG_KVM_BOOK3S_HV_POSSIBLE)
diff --git a/arch/powerpc/platforms/85xx/smp.c b/arch/powerpc/platforms/85xx/smp.c
index 078097a0b09d..fccc17fffbe7 100644
--- a/arch/powerpc/platforms/85xx/smp.c
+++ b/arch/powerpc/platforms/85xx/smp.c
@@ -461,16 +461,9 @@ static void mpc85xx_smp_machine_kexec(struct kimage *image)
 }
 #endif /* CONFIG_KEXEC_CORE */
 
-static void smp_85xx_basic_setup(int cpu_nr)
-{
-	if (cpu_has_feature(CPU_FTR_DBELL))
-		doorbell_setup_this_cpu();
-}
-
 static void smp_85xx_setup_cpu(int cpu_nr)
 {
 	mpic_setup_this_cpu();
-	smp_85xx_basic_setup(cpu_nr);
 }
 
 void __init mpc85xx_smp_init(void)
@@ -484,7 +477,7 @@ void __init mpc85xx_smp_init(void)
 		smp_85xx_ops.setup_cpu = smp_85xx_setup_cpu;
 		smp_85xx_ops.message_pass = smp_mpic_message_pass;
 	} else
-		smp_85xx_ops.setup_cpu = smp_85xx_basic_setup;
+		smp_85xx_ops.setup_cpu = NULL;
 
 	if (cpu_has_feature(CPU_FTR_DBELL)) {
 		/*
@@ -492,7 +485,7 @@ void __init mpc85xx_smp_init(void)
 		 * smp_muxed_ipi_message_pass
 		 */
 		smp_85xx_ops.message_pass = NULL;
-		smp_85xx_ops.cause_ipi = doorbell_cause_ipi;
+		smp_85xx_ops.cause_ipi = global_doorbell_cause_ipi;
 		smp_85xx_ops.probe = NULL;
 	}
 
diff --git a/arch/powerpc/platforms/powermac/smp.c b/arch/powerpc/platforms/powermac/smp.c
index 746ca7321b03..a3207cea360e 100644
--- a/arch/powerpc/platforms/powermac/smp.c
+++ b/arch/powerpc/platforms/powermac/smp.c
@@ -172,7 +172,7 @@ static irqreturn_t psurge_ipi_intr(int irq, void *d)
 	return IRQ_HANDLED;
 }
 
-static void smp_psurge_cause_ipi(int cpu, unsigned long data)
+static void smp_psurge_cause_ipi(int cpu)
 {
 	psurge_set_ipi(cpu);
 }
diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c
index 8b67e1eefb5c..c86b3693bcae 100644
--- a/arch/powerpc/platforms/powernv/smp.c
+++ b/arch/powerpc/platforms/powernv/smp.c
@@ -49,11 +49,6 @@ static void pnv_smp_setup_cpu(int cpu)
 {
 	if (cpu != boot_cpuid)
 		xics_setup_cpu();
-
-#ifdef CONFIG_PPC_DOORBELL
-	if (cpu_has_feature(CPU_FTR_DBELL))
-		doorbell_setup_this_cpu();
-#endif
 }
 
 static int pnv_smp_kick_cpu(int nr)
@@ -252,10 +247,28 @@ static int pnv_cpu_bootable(unsigned int nr)
 	return smp_generic_cpu_bootable(nr);
 }
 
+static void pnv_cause_ipi(int cpu)
+{
+	if (try_core_doorbell_cause_ipi(cpu))
+		return;
+	icp_ops->cause_ipi(cpu);
+}
+
+static __init void pnv_smp_probe(void)
+{
+	xics_smp_probe();
+
+	if (cpu_has_feature(CPU_FTR_DBELL) && !cpu_has_feature(CPU_FTR_ARCH_300)) {
+		smp_ops->cause_ipi = pnv_cause_ipi;
+	} else {
+		smp_ops->cause_ipi = icp_ops->cause_ipi;
+	}
+}
+
 static struct smp_ops_t pnv_smp_ops = {
-	.message_pass	= smp_muxed_ipi_message_pass,
-	.cause_ipi	= NULL,	/* Filled at runtime by xics_smp_probe() */
-	.probe		= xics_smp_probe,
+	.message_pass	= NULL, /* Use smp_muxed_ipi_message_pass */
+	.cause_ipi	= NULL,	/* Filled at runtime by pnv_smp_probe() */
+	.probe		= pnv_smp_probe,
 	.kick_cpu	= pnv_smp_kick_cpu,
 	.setup_cpu	= pnv_smp_setup_cpu,
 	.cpu_bootable	= pnv_cpu_bootable,
diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c
index 1fa08155206b..06e04b6ef67e 100644
--- a/arch/powerpc/platforms/pseries/smp.c
+++ b/arch/powerpc/platforms/pseries/smp.c
@@ -55,11 +55,6 @@
  */
 static cpumask_var_t of_spin_mask;
 
-/*
- * If we multiplex IPI mechanisms, store the appropriate XICS IPI mechanism here
- */
-static void  (*xics_cause_ipi)(int cpu, unsigned long data);
-
 /* Query where a cpu is now.  Return codes #defined in plpar_wrappers.h */
 int smp_query_cpu_stopped(unsigned int pcpu)
 {
@@ -143,8 +138,6 @@ static void smp_setup_cpu(int cpu)
 {
 	if (cpu != boot_cpuid)
 		xics_setup_cpu();
-	if (cpu_has_feature(CPU_FTR_DBELL))
-		doorbell_setup_this_cpu();
 
 	if (firmware_has_feature(FW_FEATURE_SPLPAR))
 		vpa_init(cpu);
@@ -187,13 +180,12 @@ static int smp_pSeries_kick_cpu(int nr)
 	return 0;
 }
 
-/* Only used on systems that support multiple IPI mechanisms */
-static void pSeries_cause_ipi_mux(int cpu, unsigned long data)
+static void smp_pseries_cause_ipi(int cpu)
 {
-	if (cpumask_test_cpu(cpu, cpu_sibling_mask(smp_processor_id())))
-		doorbell_cause_ipi(cpu, data);
-	else
-		xics_cause_ipi(cpu, data);
+	/* POWER9 should not use this handler */
+	if (try_core_doorbell_cause_ipi(cpu))
+		return;
+	icp_ops->cause_ipi(cpu);
 }
 
 static __init void pSeries_smp_probe(void)
@@ -205,15 +197,15 @@ static __init void pSeries_smp_probe(void)
 	 * siblings do not necessarily run on physical cores at the same
 	 * time. This could be enabled for pHyp.
 	 */
-	if (cpu_has_feature(CPU_FTR_DBELL) && !cpu_has_feature(CPU_FTR_ARCH_300)) {
-		xics_cause_ipi = smp_ops->cause_ipi;
-		smp_ops->cause_ipi = pSeries_cause_ipi_mux;
-	}
+	if (cpu_has_feature(CPU_FTR_DBELL) && !cpu_has_feature(CPU_FTR_ARCH_300))
+		smp_ops->cause_ipi = smp_pseries_cause_ipi;
+	else
+		smp_ops->cause_ipi = icp_ops->cause_ipi;
 }
 
 static struct smp_ops_t pseries_smp_ops = {
 	.message_pass	= NULL,	/* Use smp_muxed_ipi_message_pass */
-	.cause_ipi	= NULL,	/* Filled at runtime by pSeries_smp_probe() */
+	.cause_ipi	= NULL, /* Filled at runtime by pSeries_smp_probe */
 	.probe		= pSeries_smp_probe,
 	.kick_cpu	= smp_pSeries_kick_cpu,
 	.setup_cpu	= smp_setup_cpu,
diff --git a/arch/powerpc/sysdev/xics/icp-hv.c b/arch/powerpc/sysdev/xics/icp-hv.c
index e7fa26c4ff73..bbc839a98c41 100644
--- a/arch/powerpc/sysdev/xics/icp-hv.c
+++ b/arch/powerpc/sysdev/xics/icp-hv.c
@@ -138,7 +138,7 @@ static void icp_hv_set_cpu_priority(unsigned char cppr)
 
 #ifdef CONFIG_SMP
 
-static void icp_hv_cause_ipi(int cpu, unsigned long data)
+static void icp_hv_cause_ipi(int cpu)
 {
 	icp_hv_set_qirr(cpu, IPI_PRIORITY);
 }
diff --git a/arch/powerpc/sysdev/xics/icp-native.c b/arch/powerpc/sysdev/xics/icp-native.c
index 8a6a043e239b..f9e2f8b2e3eb 100644
--- a/arch/powerpc/sysdev/xics/icp-native.c
+++ b/arch/powerpc/sysdev/xics/icp-native.c
@@ -143,19 +143,9 @@ static unsigned int icp_native_get_irq(void)
 
 #ifdef CONFIG_SMP
 
-static void icp_native_cause_ipi(int cpu, unsigned long data)
+static void icp_native_cause_ipi(int cpu)
 {
 	kvmppc_set_host_ipi(cpu, 1);
-#ifdef CONFIG_PPC_DOORBELL
-	if (cpu_has_feature(CPU_FTR_DBELL)) {
-		if (cpumask_test_cpu(cpu, cpu_sibling_mask(get_cpu()))) {
-			doorbell_cause_ipi(cpu, data);
-			put_cpu();
-			return;
-		}
-		put_cpu();
-	}
-#endif
 	icp_native_set_qirr(cpu, IPI_PRIORITY);
 }
 
diff --git a/arch/powerpc/sysdev/xics/icp-opal.c b/arch/powerpc/sysdev/xics/icp-opal.c
index b53f80f0b4d8..c71d2ea42627 100644
--- a/arch/powerpc/sysdev/xics/icp-opal.c
+++ b/arch/powerpc/sysdev/xics/icp-opal.c
@@ -126,7 +126,7 @@ static void icp_opal_eoi(struct irq_data *d)
 
 #ifdef CONFIG_SMP
 
-static void icp_opal_cause_ipi(int cpu, unsigned long data)
+static void icp_opal_cause_ipi(int cpu)
 {
 	int hw_cpu = get_hard_smp_processor_id(cpu);
 
diff --git a/arch/powerpc/sysdev/xics/xics-common.c b/arch/powerpc/sysdev/xics/xics-common.c
index 23efe4e42172..2eb53c12ee6e 100644
--- a/arch/powerpc/sysdev/xics/xics-common.c
+++ b/arch/powerpc/sysdev/xics/xics-common.c
@@ -143,9 +143,6 @@ static void xics_request_ipi(void)
 
 void __init xics_smp_probe(void)
 {
-	/* Setup cause_ipi callback  based on which ICP is used */
-	smp_ops->cause_ipi = icp_ops->cause_ipi;
-
 	/* Register all the IPIs */
 	xics_request_ipi();
 }
-- 
2.11.0

[PATCH 3/5] powerpc: Introduce msgsnd/doorbell barrier primitives

[Nicholas Piggin]

POWER9 changes requirements and adds new instructions for
synchronization.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/include/asm/dbell.h | 22 ++++++++++++++++++++++
 arch/powerpc/include/asm/smp.h   |  1 +
 arch/powerpc/kernel/dbell.c      |  8 +++++---
 arch/powerpc/kernel/smp.c        | 10 ++++++++--
 4 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/dbell.h b/arch/powerpc/include/asm/dbell.h
index 5a7301f333a4..4db4cfdd829c 100644
--- a/arch/powerpc/include/asm/dbell.h
+++ b/arch/powerpc/include/asm/dbell.h
@@ -44,6 +44,17 @@ static inline void _ppc_msgsnd(u32 msg)
 		__asm__ __volatile__ (PPC_MSGSNDP(%0) : : "r" (msg));
 }
 
+/* sync before sending message */
+static inline void ppc_msgsnd_sync(void)
+{
+	__asm__ __volatile__ ("sync" : : : "memory");
+}
+
+/* sync after taking message interrupt */
+static inline void ppc_msgsync(void)
+{
+}
+
 #else /* CONFIG_PPC_BOOK3S */
 
 #define PPC_DBELL_MSGTYPE		PPC_DBELL
@@ -53,6 +64,17 @@ static inline void _ppc_msgsnd(u32 msg)
 	__asm__ __volatile__ (PPC_MSGSND(%0) : : "r" (msg));
 }
 
+/* sync before sending message */
+static inline void ppc_msgsnd_sync(void)
+{
+	__asm__ __volatile__ ("sync" : : : "memory");
+}
+
+/* sync after taking message interrupt */
+static inline void ppc_msgsync(void)
+{
+}
+
 #endif /* CONFIG_PPC_BOOK3S */
 
 extern void global_doorbell_cause_ipi(int cpu);
diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
index 0ada12e61fd7..0ee8a6cb1d87 100644
--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h
@@ -128,6 +128,7 @@ extern const char *smp_ipi_name[];
 extern void smp_muxed_ipi_message_pass(int cpu, int msg);
 extern void smp_muxed_ipi_set_message(int cpu, int msg);
 extern irqreturn_t smp_ipi_demux(void);
+extern irqreturn_t smp_ipi_demux_relaxed(void);
 
 void smp_init_pSeries(void);
 void smp_init_cell(void);
diff --git a/arch/powerpc/kernel/dbell.c b/arch/powerpc/kernel/dbell.c
index 2b41f145de05..98de6d3d904e 100644
--- a/arch/powerpc/kernel/dbell.c
+++ b/arch/powerpc/kernel/dbell.c
@@ -38,7 +38,7 @@ void global_doorbell_cause_ipi(int cpu)
 
 	kvmppc_set_host_ipi(cpu, 1);
 	/* Order previous accesses vs. msgsnd, which is treated as a store */
-	mb();
+	ppc_msgsnd_sync();
 	ppc_msgsnd(PPC_DBELL_MSGTYPE, 0, tag);
 }
 
@@ -53,7 +53,7 @@ void core_doorbell_cause_ipi(int cpu)
 
 	kvmppc_set_host_ipi(cpu, 1);
 	/* Order previous accesses vs. msgsnd, which is treated as a store */
-	mb();
+	ppc_msgsnd_sync();
 	ppc_msgsnd(PPC_DBELL_MSGTYPE, 0, tag);
 }
 
@@ -82,12 +82,14 @@ void doorbell_exception(struct pt_regs *regs)
 
 	irq_enter();
 
+	ppc_msgsync();
+
 	may_hard_irq_enable();
 
 	kvmppc_set_host_ipi(smp_processor_id(), 0);
 	__this_cpu_inc(irq_stat.doorbell_irqs);
 
-	smp_ipi_demux();
+	smp_ipi_demux_relaxed(); /* already performed the barrier */
 
 	irq_exit();
 	set_irq_regs(old_regs);
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index f1f6e4e3906b..fd2441591b81 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -246,11 +246,17 @@ void smp_muxed_ipi_message_pass(int cpu, int msg)
 
 irqreturn_t smp_ipi_demux(void)
 {
+	mb();	/* order any irq clear */
+
+	return smp_ipi_demux_relaxed();
+}
+
+/* sync-free variant. Callers should ensure synchronization */
+irqreturn_t smp_ipi_demux_relaxed(void)
+{
 	struct cpu_messages *info;
 	unsigned long all;
 
-	mb();	/* order any irq clear */
-
 	info = this_cpu_ptr(&ipi_message);
 	do {
 		all = xchg(&info->messages, 0);
-- 
2.11.0

[PATCH 4/5] powerpc/64s: avoid branch for ppc_msgsnd

[Nicholas Piggin]

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/include/asm/dbell.h | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/dbell.h b/arch/powerpc/include/asm/dbell.h
index 4db4cfdd829c..8ad66ccb7180 100644
--- a/arch/powerpc/include/asm/dbell.h
+++ b/arch/powerpc/include/asm/dbell.h
@@ -38,10 +38,8 @@ enum ppc_dbell {
 
 static inline void _ppc_msgsnd(u32 msg)
 {
-	if (cpu_has_feature(CPU_FTR_HVMODE))
-		__asm__ __volatile__ (PPC_MSGSND(%0) : : "r" (msg));
-	else
-		__asm__ __volatile__ (PPC_MSGSNDP(%0) : : "r" (msg));
+	__asm__ __volatile__ (ASM_FTR_IFSET(PPC_MSGSND(%1), PPC_MSGSNDP(%1), %0)
+				: : "i" (CPU_FTR_HVMODE), "r" (msg));
 }
 
 /* sync before sending message */
-- 
2.11.0

[PATCH 5/5] powerpc/powernv: POWER9 support for msgsnd/doorbell IPI

[Nicholas Piggin]

POWER9 requires msgsync for receiver-side synchronization,
and a DD1 workaround that uses the darn instruction.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/include/asm/dbell.h          |  8 ++++++++
 arch/powerpc/include/asm/feature-fixups.h | 20 ++++++++++++++++++++
 arch/powerpc/include/asm/ppc-opcode.h     |  6 ++++++
 arch/powerpc/include/asm/ppc_asm.h        | 15 +++++++++++++++
 arch/powerpc/platforms/powernv/smp.c      |  8 ++++++--
 5 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/dbell.h b/arch/powerpc/include/asm/dbell.h
index 8ad66ccb7180..2cdad4381045 100644
--- a/arch/powerpc/include/asm/dbell.h
+++ b/arch/powerpc/include/asm/dbell.h
@@ -51,6 +51,14 @@ static inline void ppc_msgsnd_sync(void)
 /* sync after taking message interrupt */
 static inline void ppc_msgsync(void)
 {
+	/* sync is not required when taking messages from the same core */
+	if (cpu_has_feature(CPU_FTR_ARCH_300) && cpu_has_feature(CPU_FTR_HVMODE)) {
+		unsigned long reg;
+		__asm__ __volatile__ (ASM_FTR_IFCLR(
+			PPC_MSGSYNC " ; lwsync",
+			PPC_DARN(%0, 2) " ; lwsync",
+			%1) : "=r" (reg) : "i" (CPU_FTR_POWER9_DD1) : "memory");
+	}
 }
 
 #else /* CONFIG_PPC_BOOK3S */
diff --git a/arch/powerpc/include/asm/feature-fixups.h b/arch/powerpc/include/asm/feature-fixups.h
index ddf54f5bbdd1..d6b8c9a20496 100644
--- a/arch/powerpc/include/asm/feature-fixups.h
+++ b/arch/powerpc/include/asm/feature-fixups.h
@@ -66,7 +66,14 @@ label##5:							\
 #define END_FTR_SECTION(msk, val)		\
 	END_FTR_SECTION_NESTED(msk, val, 97)
 
+#define END_FTR_SECTION_NESTED_IFSET(msk, label) \
+	END_FTR_SECTION_NESTED((msk), (msk), label)
+
 #define END_FTR_SECTION_IFSET(msk)	END_FTR_SECTION((msk), (msk))
+
+#define END_FTR_SECTION_NESTED_IFCLR(msk, label) \
+	END_FTR_SECTION_NESTED((msk), 0, label)
+
 #define END_FTR_SECTION_IFCLR(msk)	END_FTR_SECTION((msk), 0)
 
 /* CPU feature sections with alternatives, use BEGIN_FTR_SECTION to start */
@@ -153,12 +160,25 @@ label##5:							\
 	section_else "; "					\
 	stringify_in_c(ALT_FTR_SECTION_END((msk), (val)))
 
+#define ASM_FTR_IF_NESTED(section_if, section_else, msk, val, label)	\
+	stringify_in_c(BEGIN_FTR_SECTION_NESTED(label))		\
+	section_if "; "						\
+	stringify_in_c(FTR_SECTION_ELSE_NESTED(label))		\
+	section_else "; "					\
+	stringify_in_c(ALT_FTR_SECTION_END_NESTED((msk), (val), label))
+
 #define ASM_FTR_IFSET(section_if, section_else, msk)	\
 	ASM_FTR_IF(section_if, section_else, (msk), (msk))
 
+#define ASM_FTR_IFSET_NESTED(section_if, section_else, msk, label)	\
+	ASM_FTR_IF(section_if, section_else, (msk), (msk), label)
+
 #define ASM_FTR_IFCLR(section_if, section_else, msk)	\
 	ASM_FTR_IF(section_if, section_else, (msk), 0)
 
+#define ASM_FTR_IFCLR_NESTED(section_if, section_else, msk, label)	\
+	ASM_FTR_IF(section_if, section_else, (msk), 0, label)
+
 #define ASM_MMU_FTR_IF(section_if, section_else, msk, val)	\
 	stringify_in_c(BEGIN_MMU_FTR_SECTION)			\
 	section_if "; "						\
diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
index e7d6d86563ee..44009dfeab69 100644
--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h
@@ -134,6 +134,7 @@
 #define PPC_INST_COPY			0x7c00060c
 #define PPC_INST_COPY_FIRST		0x7c20060c
 #define PPC_INST_CP_ABORT		0x7c00068c
+#define PPC_INST_DARN			0x7c0005e6
 #define PPC_INST_DCBA			0x7c0005ec
 #define PPC_INST_DCBA_MASK		0xfc0007fe
 #define PPC_INST_DCBAL			0x7c2005ec
@@ -161,6 +162,7 @@
 #define PPC_INST_MFTMR			0x7c0002dc
 #define PPC_INST_MSGSND			0x7c00019c
 #define PPC_INST_MSGCLR			0x7c0001dc
+#define PPC_INST_MSGSYNC		0x7c0006ec
 #define PPC_INST_MSGSNDP		0x7c00011c
 #define PPC_INST_MTTMR			0x7c0003dc
 #define PPC_INST_NOP			0x60000000
@@ -310,6 +312,7 @@
 #define __PPC_XS(s)	((((s) & 0x1f) << 21) | (((s) & 0x20) >> 5))
 #define __PPC_XT(s)	__PPC_XS(s)
 #define __PPC_T_TLB(t)	(((t) & 0x3) << 21)
+#define __PPC_L_DARN(l)	(((l) & 0x3) << 16)
 #define __PPC_WC(w)	(((w) & 0x3) << 21)
 #define __PPC_WS(w)	(((w) & 0x1f) << 11)
 #define __PPC_SH(s)	__PPC_WS(s)
@@ -333,6 +336,8 @@
 
 /* Deal with instructions that older assemblers aren't aware of */
 #define	PPC_CP_ABORT		stringify_in_c(.long PPC_INST_CP_ABORT)
+#define	PPC_DARN(t, l)		stringify_in_c(.long PPC_INST_DARN | \
+					___PPC_RT(t) | __PPC_L_DARN(l))
 #define	PPC_DCBAL(a, b)		stringify_in_c(.long PPC_INST_DCBAL | \
 					__PPC_RA(a) | __PPC_RB(b))
 #define	PPC_DCBZL(a, b)		stringify_in_c(.long PPC_INST_DCBZL | \
@@ -345,6 +350,7 @@
 					___PPC_RB(b) | __PPC_EH(eh))
 #define PPC_MSGSND(b)		stringify_in_c(.long PPC_INST_MSGSND | \
 					___PPC_RB(b))
+#define PPC_MSGSYNC		stringify_in_c(.long PPC_INST_MSGSYNC)
 #define PPC_MSGCLR(b)		stringify_in_c(.long PPC_INST_MSGCLR | \
 					___PPC_RB(b))
 #define PPC_MSGSNDP(b)		stringify_in_c(.long PPC_INST_MSGSNDP | \
diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
index 359c44341761..8ab5dc554ca5 100644
--- a/arch/powerpc/include/asm/ppc_asm.h
+++ b/arch/powerpc/include/asm/ppc_asm.h
@@ -402,6 +402,21 @@ END_FTR_SECTION_IFCLR(CPU_FTR_601)
 	FTR_SECTION_ELSE_NESTED(848);	\
 	mtocrf (FXM), RS;		\
 	ALT_FTR_SECTION_END_NESTED_IFCLR(CPU_FTR_NOEXECUTE, 848)
+
+#if defined(CONFIG_BOOKS)
+#define MSGSYNC(reg)			\
+	BEGIN_FTR_SECTION_NESTED(849);	\
+					\
+	BEGIN_FTR_SECTION_NESTED(850);	\
+	PPC_MSGSYNC;			\
+	lwsync;				\
+	FTR_SECTION_ELSE_NESTED(850);	\
+	PPC_DARN(reg, 2);		\
+	lwsync;				\
+	ALT_FTR_SECTION_END_NESTED_IFCLR(CPU_FTR_POWER9_DD1, 850); \
+					\
+	END_FTR_SECTION_NESTED_IFSET(CPU_FTR_HVMODE|CPU_FTR_ARCH_300, 849)
+#endif
 #endif
 
 /*
diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c
index c86b3693bcae..45a7efa3f03c 100644
--- a/arch/powerpc/platforms/powernv/smp.c
+++ b/arch/powerpc/platforms/powernv/smp.c
@@ -249,6 +249,7 @@ static int pnv_cpu_bootable(unsigned int nr)
 
 static void pnv_cause_ipi(int cpu)
 {
+	/* Pre-POWER9 has only core-local dbell IPIs. Must fall back to IC. */
 	if (try_core_doorbell_cause_ipi(cpu))
 		return;
 	icp_ops->cause_ipi(cpu);
@@ -258,8 +259,11 @@ static __init void pnv_smp_probe(void)
 {
 	xics_smp_probe();
 
-	if (cpu_has_feature(CPU_FTR_DBELL) && !cpu_has_feature(CPU_FTR_ARCH_300)) {
-		smp_ops->cause_ipi = pnv_cause_ipi;
+	if (cpu_has_feature(CPU_FTR_DBELL)) {
+		if (cpu_has_feature(CPU_FTR_ARCH_300))
+			smp_ops->cause_ipi = global_doorbell_cause_ipi;
+		else
+			smp_ops->cause_ipi = pnv_cause_ipi;
 	} else {
 		smp_ops->cause_ipi = icp_ops->cause_ipi;
 	}
-- 
2.11.0

Re: [PATCH 1/5] powerpc/pseries: do not use msgsndp doorbells on POWER9 guests

[Benjamin Herrenschmidt]

On Fri, 2017-04-07 at 22:55 +1000, Nicholas Piggin wrote:
> POWER9 hypervisors will not necessarily run guest threads together on
> the same core at the same time, so msgsndp should not be used.

Maybe we shouldn't advertise doorbells at all ?

> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>  arch/powerpc/platforms/pseries/smp.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/smp.c
> b/arch/powerpc/platforms/pseries/smp.c
> index f6f83aeccaaa..1fa08155206b 100644
> --- a/arch/powerpc/platforms/pseries/smp.c
> +++ b/arch/powerpc/platforms/pseries/smp.c
> @@ -200,7 +200,12 @@ static __init void pSeries_smp_probe(void)
>  {
>  	xics_smp_probe();
>  
> -	if (cpu_has_feature(CPU_FTR_DBELL)) {
> +	/*
> +	 * POWER9 can not use msgsndp doorbells for IPI because
> thread
> +	 * siblings do not necessarily run on physical cores at the
> same
> +	 * time. This could be enabled for pHyp.
> +	 */
> +	if (cpu_has_feature(CPU_FTR_DBELL) &&
> !cpu_has_feature(CPU_FTR_ARCH_300)) {
>  		xics_cause_ipi = smp_ops->cause_ipi;
>  		smp_ops->cause_ipi = pSeries_cause_ipi_mux;
>  	}

Re: [PATCH 1/5] powerpc/pseries: do not use msgsndp doorbells on POWER9 guests

[Nicholas Piggin]

On Sun, 09 Apr 2017 18:03:35 +1000
Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:

> On Fri, 2017-04-07 at 22:55 +1000, Nicholas Piggin wrote:
> > POWER9 hypervisors will not necessarily run guest threads together on
> > the same core at the same time, so msgsndp should not be used.  
> 
> Maybe we shouldn't advertise doorbells at all ?

Possibly not. I don't know if there is a good way to switch it off
in the guest from the host with device tree currently. Might be better
to clear it early in the guest rather than test it here though?

Thanks,
Nick

Re: [PATCH 1/5] powerpc/pseries: do not use msgsndp doorbells on POWER9 guests

[Benjamin Herrenschmidt]

On Mon, 2017-04-10 at 13:22 +1000, Nicholas Piggin wrote:
> On Sun, 09 Apr 2017 18:03:35 +1000
> > Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> 
> > On Fri, 2017-04-07 at 22:55 +1000, Nicholas Piggin wrote:
> > > POWER9 hypervisors will not necessarily run guest threads together on
> > > the same core at the same time, so msgsndp should not be used.  
> > 
> > Maybe we shouldn't advertise doorbells at all ?
> 
> Possibly not. I don't know if there is a good way to switch it off
> in the guest from the host with device tree currently. Might be better
> to clear it early in the guest rather than test it here though?

Sure for now. Long term a separate DT entry would be good. Might be
worth re-enabling one day if we have HW virtualization of geust
doorbells.

Cheers,
Ben

Re: [PATCH 1/5] powerpc/pseries: do not use msgsndp doorbells on POWER9 guests

[Nicholas Piggin]

On Mon, 10 Apr 2017 14:07:38 +1000
Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:

> On Mon, 2017-04-10 at 13:22 +1000, Nicholas Piggin wrote:
> > On Sun, 09 Apr 2017 18:03:35 +1000  
> > > Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:  
> >   
> > > On Fri, 2017-04-07 at 22:55 +1000, Nicholas Piggin wrote:  
> > > > POWER9 hypervisors will not necessarily run guest threads together on
> > > > the same core at the same time, so msgsndp should not be used.    
> > > 
> > > Maybe we shouldn't advertise doorbells at all ?  
> > 
> > Possibly not. I don't know if there is a good way to switch it off
> > in the guest from the host with device tree currently. Might be better
> > to clear it early in the guest rather than test it here though?  
> 
> Sure for now. Long term a separate DT entry would be good.

cpufeatures will do that, but I wonder if some hypervisors won't implement
that binding then might be worth getting into an existing one in PAPR.

Anyway for now I'll make the change and have P9 guest clear the feature
themselves if you like.

> Might be
> worth re-enabling one day if we have HW virtualization of geust
> doorbells.

Yes. Also some hypervisor might run in a virtual sibling = physical
sibling mode on P9 too where it could still work.

Thanks,
Nick

Re: [PATCH 1/5] powerpc/pseries: do not use msgsndp doorbells on POWER9 guests

[Michael Ellerman]

Nicholas Piggin <npiggin@gmail.com> writes:

> POWER9 hypervisors will not necessarily run guest threads together on
> the same core at the same time, so msgsndp should not be used.

I'm worried this is encoding the behaviour of a particular hypervisor in
the guest kernel.

If we *can't* use msgsndp then the hypervisor better do something to
stop us from using it.

If it would be preferable for us not to use msgsndp, then the hypervisor
can tell us that somehow, eg. in the device tree.

?

cheers

Re: [PATCH 1/5] powerpc/pseries: do not use msgsndp doorbells on POWER9 guests

[Nicholas Piggin]

cc'ing Paul

On Tue, 11 Apr 2017 20:10:17 +1000
Michael Ellerman <mpe@ellerman.id.au> wrote:

> Nicholas Piggin <npiggin@gmail.com> writes:
> 
> > POWER9 hypervisors will not necessarily run guest threads together on
> > the same core at the same time, so msgsndp should not be used.  
> 
> I'm worried this is encoding the behaviour of a particular hypervisor in
> the guest kernel.

Yeah, it's not ideal.

> If we *can't* use msgsndp then the hypervisor better do something to
> stop us from using it.

POWER9 hypervisor has an hfscr and should clear that if it does not gang
threads like POWER8. The guest still needs to know not to use it though...

> If it would be preferable for us not to use msgsndp, then the hypervisor
> can tell us that somehow, eg. in the device tree.

I don't know that we have a really good way to do that other than guests
to clear the doorbell feature for POWER9.

Does the hypervisor set any relevant DT we can use today that says virtual
sibling != physical sibling? If not, then we'll just have to clear it from
all POWER9 guests until we get a DT proprety from phyp.

Thanks,
Nick