Subject: [RFC PATCH 3/5] powerpc/64s: add CONFIG_PPC_NMMU for nest MMU support

From: Nicholas Piggin <[email-masked]>
Date: Sun, 20 Dec 2020 09:48:11 +1000

This allows some nest MMU features to be compiled away if coprocessor
support is not selected.

Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/Kconfig                          | 1 +
 arch/powerpc/include/asm/book3s/64/mmu.h      | 2 ++
 arch/powerpc/include/asm/book3s/64/tlbflush.h | 2 ++
 arch/powerpc/include/asm/mmu_context.h        | 5 +++--
 arch/powerpc/platforms/Kconfig                | 3 +++
 arch/powerpc/platforms/powernv/Kconfig        | 1 +
 6 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index ae7391627054..4376bf4c53b4 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -888,6 +888,7 @@ config PPC_PROT_SAO_LPAR
 
 config PPC_COPRO_BASE
 	bool
+	select PPC_NMMU if PPC_BOOK3S_64
 
 config SCHED_SMT
 	bool "SMT (Hyperthreading) scheduler support"
diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
index 995bbcdd0ef8..07850d68a624 100644
--- a/arch/powerpc/include/asm/book3s/64/mmu.h
+++ b/arch/powerpc/include/asm/book3s/64/mmu.h
@@ -103,8 +103,10 @@ typedef struct {
 	/* Number of bits in the mm_cpumask */
 	atomic_t active_cpus;
 
+#ifdef CONFIG_PPC_NMMU
 	/* Number of users of the external (Nest) MMU */
 	atomic_t copros;
+#endif
 
 	/* Number of user space windows opened in process mm_context */
 	atomic_t vas_windows;
diff --git a/arch/powerpc/include/asm/book3s/64/tlbflush.h b/arch/powerpc/include/asm/book3s/64/tlbflush.h
index 0a7431e954c6..c70a82851f78 100644
--- a/arch/powerpc/include/asm/book3s/64/tlbflush.h
+++ b/arch/powerpc/include/asm/book3s/64/tlbflush.h
@@ -16,8 +16,10 @@ enum {
 
 static inline bool mm_has_nmmu(struct mm_struct *mm)
 {
+#ifdef CONFIG_PPC_NMMU
 	if (unlikely(atomic_read(&mm->context.copros) > 0))
 		return true;
+#endif
 	return false;
 }
 
diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index d5821834dba9..53eac0cc4929 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -143,6 +143,7 @@ static inline void dec_mm_active_cpus(struct mm_struct *mm)
 	atomic_dec(&mm->context.active_cpus);
 }
 
+#ifdef CONFIG_PPC_NMMU
 static inline void mm_context_add_copro(struct mm_struct *mm)
 {
 	/*
@@ -187,6 +188,7 @@ static inline void mm_context_remove_copro(struct mm_struct *mm)
 			dec_mm_active_cpus(mm);
 	}
 }
+#endif
 
 /*
  * vas_windows counter shows number of open windows in the mm
@@ -218,8 +220,7 @@ static inline void mm_context_remove_vas_window(struct mm_struct *mm)
 #else
 static inline void inc_mm_active_cpus(struct mm_struct *mm) { }
 static inline void dec_mm_active_cpus(struct mm_struct *mm) { }
-static inline void mm_context_add_copro(struct mm_struct *mm) { }
-static inline void mm_context_remove_copro(struct mm_struct *mm) { }
+static inline bool mm_has_nmmu(struct mm_struct *mm) { return false; }
 #endif

diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
index 7a5e8f4541e3..b4b04b3f98d1 100644
--- a/arch/powerpc/platforms/Kconfig
+++ b/arch/powerpc/platforms/Kconfig
@@ -191,6 +191,9 @@ config PPC_INDIRECT_MMIO
 config PPC_IO_WORKAROUNDS
 	bool
 
+config PPC_NMMU
+	bool
+
 source "drivers/cpufreq/Kconfig"
 
 menu "CPUIdle driver"
diff --git a/arch/powerpc/platforms/powernv/Kconfig b/arch/powerpc/platforms/powernv/Kconfig
index 619b093a0657..145009d74457 100644
--- a/arch/powerpc/platforms/powernv/Kconfig
+++ b/arch/powerpc/platforms/powernv/Kconfig
@@ -36,6 +36,7 @@ config PPC_MEMTRACE
 config PPC_VAS
 	bool "IBM Virtual Accelerator Switchboard (VAS)"
 	depends on PPC_POWERNV && PPC_64K_PAGES
+	select PPC_NMMU
 	default y
 	help
 	  This enables support for IBM Virtual Accelerator Switchboard (VAS).
-- 
2.23.0