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Diffstat (limited to 'arch/arm64/mm/context.c')
-rw-r--r--arch/arm64/mm/context.c38
1 files changed, 30 insertions, 8 deletions
diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
index b5e329fde2dd..8ef73e89d514 100644
--- a/arch/arm64/mm/context.c
+++ b/arch/arm64/mm/context.c
@@ -29,15 +29,9 @@ static cpumask_t tlb_flush_pending;
#define ASID_MASK (~GENMASK(asid_bits - 1, 0))
#define ASID_FIRST_VERSION (1UL << asid_bits)
-#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
-#define NUM_USER_ASIDS (ASID_FIRST_VERSION >> 1)
-#define asid2idx(asid) (((asid) & ~ASID_MASK) >> 1)
-#define idx2asid(idx) (((idx) << 1) & ~ASID_MASK)
-#else
-#define NUM_USER_ASIDS (ASID_FIRST_VERSION)
+#define NUM_USER_ASIDS ASID_FIRST_VERSION
#define asid2idx(asid) ((asid) & ~ASID_MASK)
#define idx2asid(idx) asid2idx(idx)
-#endif
/* Get the ASIDBits supported by the current CPU */
static u32 get_cpu_asid_bits(void)
@@ -77,13 +71,33 @@ void verify_cpu_asid_bits(void)
}
}
+static void set_kpti_asid_bits(void)
+{
+ unsigned int len = BITS_TO_LONGS(NUM_USER_ASIDS) * sizeof(unsigned long);
+ /*
+ * In case of KPTI kernel/user ASIDs are allocated in
+ * pairs, the bottom bit distinguishes the two: if it
+ * is set, then the ASID will map only userspace. Thus
+ * mark even as reserved for kernel.
+ */
+ memset(asid_map, 0xaa, len);
+}
+
+static void set_reserved_asid_bits(void)
+{
+ if (arm64_kernel_unmapped_at_el0())
+ set_kpti_asid_bits();
+ else
+ bitmap_clear(asid_map, 0, NUM_USER_ASIDS);
+}
+
static void flush_context(void)
{
int i;
u64 asid;
/* Update the list of reserved ASIDs and the ASID bitmap. */
- bitmap_clear(asid_map, 0, NUM_USER_ASIDS);
+ set_reserved_asid_bits();
for_each_possible_cpu(i) {
asid = atomic64_xchg_relaxed(&per_cpu(active_asids, i), 0);
@@ -261,6 +275,14 @@ static int asids_init(void)
panic("Failed to allocate bitmap for %lu ASIDs\n",
NUM_USER_ASIDS);
+ /*
+ * We cannot call set_reserved_asid_bits() here because CPU
+ * caps are not finalized yet, so it is safer to assume KPTI
+ * and reserve kernel ASID's from beginning.
+ */
+ if (IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0))
+ set_kpti_asid_bits();
+
pr_info("ASID allocator initialised with %lu entries\n", NUM_USER_ASIDS);
return 0;
}