[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 <bg...@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