[PATCH] powerpc/64s: Add support for ASB_Notify on POWER9

Christophe Lombard clombard at linux.vnet.ibm.com
Sat Aug 5 00:56:12 AEST 2017


The POWER9 core supports a new feature: ASB_Notify which requires the
support of the Special Purpose Register: TIDR.

The ASB_Notify command, generated by the AFU, will attempt to
wake-up the host thread identified by the particular LPID:PID:TID.

The special register TIDR has to be updated to with the same value
present in the process element.

If the length of the register TIDR is 64bits, the CAPI Translation
Service Layer core (XSL9) for Power9 systems limits the size (16bits) of
the Thread ID when it generates the ASB_Notify message adding
PID:LPID:TID information from the context.

The content of the internal kernel Thread ID (32bits) can not therefore
be used to fulfill the register TIDR.

This patch allows to avoid this limitation by adding a new interface
for the user. The instructions mfspr/mtspr SPRN_TIDR are emulated,
save/restore SPRs (context switch) are updated and a new feature
(CPU_FTR_TIDR) is added to POWER9 system.

Signed-off-by: Christophe Lombard <clombard at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/cputable.h     |  4 +++-
 arch/powerpc/include/asm/emulated_ops.h |  2 ++
 arch/powerpc/include/asm/ppc-opcode.h   |  4 ++++
 arch/powerpc/include/asm/processor.h    |  1 +
 arch/powerpc/kernel/process.c           |  8 ++++++++
 arch/powerpc/kernel/traps.c             | 21 +++++++++++++++++++++
 6 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
index d02ad93..706f668 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -215,6 +215,7 @@ enum {
 #define CPU_FTR_DABRX			LONG_ASM_CONST(0x0800000000000000)
 #define CPU_FTR_PMAO_BUG		LONG_ASM_CONST(0x1000000000000000)
 #define CPU_FTR_POWER9_DD1		LONG_ASM_CONST(0x4000000000000000)
+#define CPU_FTR_TIDR			LONG_ASM_CONST(0x8000000000000000)
 
 #ifndef __ASSEMBLY__
 
@@ -474,7 +475,8 @@ enum {
 	    CPU_FTR_STCX_CHECKS_ADDRESS | CPU_FTR_POPCNTB | CPU_FTR_POPCNTD | \
 	    CPU_FTR_CFAR | CPU_FTR_HVMODE | CPU_FTR_VMX_COPY | \
 	    CPU_FTR_DBELL | CPU_FTR_HAS_PPR | CPU_FTR_DAWR | \
-	    CPU_FTR_ARCH_207S | CPU_FTR_TM_COMP | CPU_FTR_ARCH_300)
+	    CPU_FTR_ARCH_207S | CPU_FTR_TM_COMP | CPU_FTR_ARCH_300 | \
+	    CPU_FTR_TIDR)
 #define CPU_FTRS_POWER9_DD1 ((CPU_FTRS_POWER9 | CPU_FTR_POWER9_DD1) & \
 			     (~CPU_FTR_SAO))
 #define CPU_FTRS_CELL	(CPU_FTR_USE_TB | CPU_FTR_LWSYNC | \
diff --git a/arch/powerpc/include/asm/emulated_ops.h b/arch/powerpc/include/asm/emulated_ops.h
index f00e10e..e83ad42 100644
--- a/arch/powerpc/include/asm/emulated_ops.h
+++ b/arch/powerpc/include/asm/emulated_ops.h
@@ -54,6 +54,8 @@ extern struct ppc_emulated {
 #ifdef CONFIG_PPC64
 	struct ppc_emulated_entry mfdscr;
 	struct ppc_emulated_entry mtdscr;
+	struct ppc_emulated_entry mftidr;
+	struct ppc_emulated_entry mttidr;
 	struct ppc_emulated_entry lq_stq;
 #endif
 } ppc_emulated;
diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
index fa9ebae..3ebc446 100644
--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h
@@ -241,6 +241,10 @@
 #define PPC_INST_MFSPR_DSCR_USER_MASK	0xfc1ffffe
 #define PPC_INST_MTSPR_DSCR_USER	0x7c0303a6
 #define PPC_INST_MTSPR_DSCR_USER_MASK	0xfc1ffffe
+#define PPC_INST_MFSPR_TIDR		0x7d2452a6
+#define PPC_INST_MFSPR_TIDR_MASK	0xfd2ffffe
+#define PPC_INST_MTSPR_TIDR		0x7d2453a6
+#define PPC_INST_MTSPR_TIDR_MASK	0xfd2ffffe
 #define PPC_INST_MFVSRD			0x7c000066
 #define PPC_INST_MTVSRD			0x7c000166
 #define PPC_INST_SLBFEE			0x7c0007a7
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index fab7ff8..58cc212 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -329,6 +329,7 @@ struct thread_struct {
 	 */
 	int		dscr_inherit;
 	unsigned long	ppr;	/* used to save/restore SMT priority */
+	unsigned long	tidr;
 #endif
 #ifdef CONFIG_PPC_BOOK3S_64
 	unsigned long	tar;
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 9f3e2c9..f06ea10 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1084,6 +1084,9 @@ static inline void save_sprs(struct thread_struct *t)
 	if (cpu_has_feature(CPU_FTR_DSCR))
 		t->dscr = mfspr(SPRN_DSCR);
 
+	if (cpu_has_feature(CPU_FTR_TIDR))
+		t->tidr = mfspr(SPRN_TIDR);
+
 	if (cpu_has_feature(CPU_FTR_ARCH_207S)) {
 		t->bescr = mfspr(SPRN_BESCR);
 		t->ebbhr = mfspr(SPRN_EBBHR);
@@ -1120,6 +1123,11 @@ static inline void restore_sprs(struct thread_struct *old_thread,
 			mtspr(SPRN_DSCR, dscr);
 	}
 
+	if (cpu_has_feature(CPU_FTR_TIDR)) {
+		if (old_thread->tidr != new_thread->tidr)
+			mtspr(SPRN_TIDR, new_thread->tidr);
+	}
+
 	if (cpu_has_feature(CPU_FTR_ARCH_207S)) {
 		if (old_thread->bescr != new_thread->bescr)
 			mtspr(SPRN_BESCR, new_thread->bescr);
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index bfcfd9e..b829de7 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -1141,6 +1141,25 @@ static int emulate_instruction(struct pt_regs *regs)
 		mtspr(SPRN_DSCR, current->thread.dscr);
 		return 0;
 	}
+	/* Emulate the mfspr rD, TIDR. */
+	if (((instword & PPC_INST_MFSPR_TIDR_MASK) ==
+		PPC_INST_MFSPR_TIDR) &&
+			cpu_has_feature(CPU_FTR_TIDR)) {
+		PPC_WARN_EMULATED(mftidr, regs);
+		rd = (instword >> 21) & 0x1f;
+		regs->gpr[rd] = mfspr(SPRN_TIDR);
+		return 0;
+	}
+	/* Emulate the mtspr TIDR, rD. */
+	if (((instword & PPC_INST_MTSPR_TIDR_MASK) ==
+		PPC_INST_MTSPR_TIDR) &&
+			cpu_has_feature(CPU_FTR_TIDR)) {
+		PPC_WARN_EMULATED(mttidr, regs);
+		rd = (instword >> 21) & 0x1f;
+		current->thread.tidr = regs->gpr[rd];
+		mtspr(SPRN_TIDR, regs->gpr[rd]);
+		return 0;
+	}
 #endif
 
 	return -EINVAL;
@@ -2036,6 +2055,8 @@ struct ppc_emulated ppc_emulated = {
 #ifdef CONFIG_PPC64
 	WARN_EMULATED_SETUP(mfdscr),
 	WARN_EMULATED_SETUP(mtdscr),
+	WARN_EMULATED_SETUP(mftidr),
+	WARN_EMULATED_SETUP(mttidr),
 	WARN_EMULATED_SETUP(lq_stq),
 #endif
 };
-- 
2.7.4



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