powerpc/book3s64/kuap: Move UAMOR setup to key init function

UAMOR values are not application-specific. The kernel initializes
its value based on different reserved keys. Remove the thread-specific
UAMOR value and don't switch the UAMOR on context switch.

Move UAMOR initialization to key initialization code and remove
thread_struct.uamor because it is not used anymore.

Before commit: 4a4a5e5d2aad ("powerpc/pkeys: key allocation/deallocation must not change pkey registers")
we used to update uamor based on key allocation and free.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200709032946.881753-20-aneesh.kumar@linux.ibm.com

3 files changed, 20 insertions, 17 deletions

diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index eec6f4e5e481..9dfb0ceed5e3 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -1110,6 +1110,10 @@ void hash__early_init_mmu_secondary(void)
 	if (cpu_has_feature(CPU_FTR_ARCH_206)
 			&& cpu_has_feature(CPU_FTR_HVMODE))
 		tlbiel_all();
+
+#ifdef CONFIG_PPC_MEM_KEYS
+	mtspr(SPRN_UAMOR, default_uamor);
+#endif
 }
 #endif /* CONFIG_SMP */
 
diff --git a/arch/powerpc/mm/book3s64/pkeys.c b/arch/powerpc/mm/book3s64/pkeys.c
index e776544a4d11..d45864a77066 100644
--- a/arch/powerpc/mm/book3s64/pkeys.c
+++ b/arch/powerpc/mm/book3s64/pkeys.c
@@ -27,9 +27,7 @@ static u32 initial_allocation_mask __ro_after_init;
  */
 static u64 default_amr = ~0x0UL;
 static u64 default_iamr = 0x5555555555555555UL;
-
-/* Allow all keys to be modified by default */
-static u64 default_uamor = ~0x0UL;
+u64 default_uamor __ro_after_init;
 /*
  * Key used to implement PROT_EXEC mmap. Denies READ/WRITE
  * We pick key 2 because 0 is special key and 1 is reserved as per ISA.
@@ -122,10 +120,11 @@ void __init pkey_early_init_devtree(void)
 
 	/* scan the device tree for pkey feature */
 	pkeys_total = scan_pkey_feature();
-	if (!pkeys_total) {
-		/* No support for pkey. Mark it disabled */
-		return;
-	}
+	if (!pkeys_total)
+		goto out;
+
+	/* Allow all keys to be modified by default */
+	default_uamor = ~0x0UL;
 
 	cur_cpu_spec->mmu_features |= MMU_FTR_PKEY;
 
@@ -209,6 +208,12 @@ void __init pkey_early_init_devtree(void)
 	initial_allocation_mask |= reserved_allocation_mask;
 
 	pr_info("Enabling pkeys with max key count %d\n", num_pkey);
+out:
+	/*
+	 * Setup uamor on boot cpu
+	 */
+	mtspr(SPRN_UAMOR, default_uamor);
+
 	return;
 }
 
@@ -251,11 +256,6 @@ static inline u64 read_uamor(void)
 	return mfspr(SPRN_UAMOR);
 }
 
-static inline void write_uamor(u64 value)
-{
-	mtspr(SPRN_UAMOR, value);
-}
-
 static bool is_pkey_enabled(int pkey)
 {
 	u64 uamor = read_uamor();
@@ -326,7 +326,6 @@ void thread_pkey_regs_save(struct thread_struct *thread)
 	 */
 	thread->amr = read_amr();
 	thread->iamr = read_iamr();
-	thread->uamor = read_uamor();
 }
 
 void thread_pkey_regs_restore(struct thread_struct *new_thread,
@@ -339,8 +338,6 @@ void thread_pkey_regs_restore(struct thread_struct *new_thread,
 		write_amr(new_thread->amr);
 	if (old_thread->iamr != new_thread->iamr)
 		write_iamr(new_thread->iamr);
-	if (old_thread->uamor != new_thread->uamor)
-		write_uamor(new_thread->uamor);
 }
 
 void thread_pkey_regs_init(struct thread_struct *thread)
@@ -350,11 +347,9 @@ void thread_pkey_regs_init(struct thread_struct *thread)
 
 	thread->amr   = default_amr;
 	thread->iamr  = default_iamr;
-	thread->uamor = default_uamor;
 
 	write_amr(default_amr);
 	write_iamr(default_iamr);
-	write_uamor(default_uamor);
 }
 
 int execute_only_pkey(struct mm_struct *mm)
diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
index 3536675dd61e..a8f46a686219 100644
--- a/arch/powerpc/mm/book3s64/radix_pgtable.c
+++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
@@ -620,6 +620,10 @@ void setup_kuap(bool disabled)
 
 	/* Make sure userspace can't change the AMR */
 	mtspr(SPRN_UAMOR, 0);
+
+	/*
+	 * Set the default kernel AMR values on all cpus.
+	 */
 	mtspr(SPRN_AMR, AMR_KUAP_BLOCKED);
 	isync();
 }