This is a note to let you know that I've just added the patch titled
powerpc/dexcr: Track the DEXCR per-process
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-dexcr-track-the-dexcr-per-process.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 5236722cd74a1f92589c43b268044b1ae1be1d86
Author: Benjamin Gray <bgray@xxxxxxxxxxxxx>
Date: Wed Apr 17 21:23:18 2024 +1000
powerpc/dexcr: Track the DEXCR per-process
[ Upstream commit 75171f06c4507c3b6b5a69d793879fb20d108bb1 ]
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@xxxxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://msgid.link/20240417112325.728010-3-bgray@xxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index b2c51d337e60c..882e31296ea6b 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -260,6 +260,7 @@ struct thread_struct {
unsigned long sier2;
unsigned long sier3;
unsigned long hashkeyr;
+ unsigned long dexcr;
#endif
};
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 9452a54d356c9..d482c3fd81d7a 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 != 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;
}
diff --git a/arch/powerpc/kernel/ptrace/ptrace-view.c b/arch/powerpc/kernel/ptrace/ptrace-view.c
index 584cf5c3df509..c1819e0a66842 100644
--- a/arch/powerpc/kernel/ptrace/ptrace-view.c
+++ b/arch/powerpc/kernel/ptrace/ptrace-view.c
@@ -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
