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powerpc/dexcr: Track the DEXCR per-process

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Add capability to make the DEXCR act as a per-process SPR.

We do not yet have an interface for changing the values per task. We
also expect the kernel to use a single DEXCR value across all tasks
while in privileged state, so there is no need to synchronize after
changing it (the userspace aspects will synchronize upon returning to
userspace).

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240417112325.728010-3-bgray@linux.ibm.com
This commit is contained in:
Benjamin Gray 2024-04-17 21:23:18 +10:00 committed by Michael Ellerman
parent d7228a58d9
commit 75171f06c4
3 changed files with 12 additions and 6 deletions
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1
arch/powerpc/include/asm/processor.h
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@ -260,6 +260,7 @@ struct thread_struct {
unsigned long sier2;
unsigned long sier3;
unsigned long hashkeyr;
unsigned long dexcr;
#endif
};

10
arch/powerpc/kernel/process.c
View File

@ -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 != new_thread->dexcr)
mtspr(SPRN_DEXCR, new_thread->dexcr);
#endif
}
@ -1878,6 +1885,9 @@ 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 = mfspr(SPRN_DEXCR);
#endif
return 0;
}

7
arch/powerpc/kernel/ptrace/ptrace-view.c
View File

@ -469,12 +469,7 @@ static int dexcr_get(struct task_struct *target, const struct user_regset *regse
if (!cpu_has_feature(CPU_FTR_ARCH_31))
return -ENODEV;
/*
* The DEXCR is currently static across all CPUs, so we don't
* store the target's value anywhere, but the static value
* will also be correct.
*/
membuf_store(&to, (u64)lower_32_bits(DEXCR_INIT));
membuf_store(&to, (u64)lower_32_bits(target->thread.dexcr));
/*
* Technically the HDEXCR is per-cpu, but a hypervisor can't reasonably