[RFC PATCH 2/6] powerpc/dexcr: Add thread specific DEXCR configuration

[Benjamin Gray]

Add capability to track a DEXCR value per thread.

Nothing actually changes these values yet, but they are correctly
tracked, propagated, and used to set the hardware register.

Signed-off-by: Benjamin Gray <bgray at linux.ibm.com>
---
 arch/powerpc/include/asm/processor.h | 12 ++++++++++++
 arch/powerpc/kernel/process.c        | 24 ++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index b2c51d337e60..28a72023f9bd 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -260,6 +260,9 @@ struct thread_struct {
 	unsigned long   sier2;
 	unsigned long   sier3;
 	unsigned long	hashkeyr;
+	unsigned int	dexcr;		/* Temporary value saved during thread switch */
+	unsigned int	dexcr_enabled;	/* Bitmask of aspects enabled by this thread */
+	unsigned int	dexcr_inherit;	/* Bitmask of aspects to inherit across exec */
 
 #endif
 };
@@ -448,6 +451,15 @@ int exit_vmx_usercopy(void);
 int enter_vmx_ops(void);
 void *exit_vmx_ops(void *dest);
 
+static inline unsigned long get_thread_dexcr(struct thread_struct const *thread)
+{
+#ifdef CONFIG_PPC_BOOK3S_64
+	return thread->dexcr_enabled;
+#else
+	return 0;
+#endif
+}
+
 #endif /* __KERNEL__ */
 #endif /* __ASSEMBLY__ */
 #endif /* _ASM_POWERPC_PROCESSOR_H */
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index b68898ac07e1..c05d58b7c6b3 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1185,6 +1185,9 @@ static inline void save_sprs(struct thread_struct *t)
 
 	if (cpu_has_feature(CPU_FTR_DEXCR_NPHIE))
 		t->hashkeyr = mfspr(SPRN_HASHKEYR);
+
+	if (cpu_has_feature(CPU_FTR_ARCH_31))
+		t->dexcr = mfspr(SPRN_DEXCR);
 #endif
 }
 
@@ -1267,6 +1270,10 @@ static inline void restore_sprs(struct thread_struct *old_thread,
 	if (cpu_has_feature(CPU_FTR_DEXCR_NPHIE) &&
 	    old_thread->hashkeyr != new_thread->hashkeyr)
 		mtspr(SPRN_HASHKEYR, new_thread->hashkeyr);
+
+	if (cpu_has_feature(CPU_FTR_ARCH_31) &&
+	    old_thread->dexcr != get_thread_dexcr(new_thread))
+		mtspr(SPRN_DEXCR, get_thread_dexcr(new_thread));
 #endif
 
 }
@@ -1634,6 +1641,11 @@ void arch_setup_new_exec(void)
 	current->thread.regs->amr  = default_amr;
 	current->thread.regs->iamr  = default_iamr;
 #endif
+
+#ifdef CONFIG_PPC_BOOK3S_64
+	current->thread.dexcr_enabled &= current->thread.dexcr_inherit;
+	current->thread.dexcr_enabled |= ~current->thread.dexcr_inherit & DEXCR_INIT; 
+#endif
 }
 
 #ifdef CONFIG_PPC64
@@ -1878,6 +1890,11 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 #ifdef CONFIG_PPC_BOOK3S_64
 	if (cpu_has_feature(CPU_FTR_DEXCR_NPHIE))
 		p->thread.hashkeyr = current->thread.hashkeyr;
+
+	if (cpu_has_feature(CPU_FTR_ARCH_31)) {
+		p->thread.dexcr_enabled = current->thread.dexcr_enabled;
+		p->thread.dexcr_inherit = current->thread.dexcr_inherit;
+	}
 #endif
 	return 0;
 }
@@ -2000,6 +2017,13 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp)
 		current->thread.hashkeyr = get_random_long();
 		mtspr(SPRN_HASHKEYR, current->thread.hashkeyr);
 	}
+
+	if (cpu_has_feature(CPU_FTR_ARCH_31)) {
+		current->thread.dexcr = 0;
+		current->thread.dexcr_enabled = DEXCR_INIT;
+		current->thread.dexcr_inherit = 0;
+		mtspr(SPRN_DEXCR, get_thread_dexcr(&current->thread));
+	}
 #endif /* CONFIG_PPC_BOOK3S_64 */
 }
 EXPORT_SYMBOL(start_thread);
-- 
2.41.0