arm64: context: Fix ASID limit in boot messages

Since commit f88f42f853a8 ("arm64: context: Free up kernel ASIDs if KPTI
is not in use"), the NUM_USER_ASIDS macro doesn't correspond to the
effective number of ASIDs when KPTI is enabled. Get an accurate number
of available ASIDs in an arch_initcall, once we've discovered all CPUs'
capabilities and know if we still need to halve the ASID space for KPTI.

Fixes: f88f42f853a8 ("arm64: context: Free up kernel ASIDs if KPTI is not in use")
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
index 8ef73e8..d89bb22 100644 (file)
--- a/arch/arm64/mm/context.c
+++ b/arch/arm64/mm/context.c
@@ -260,14 +260,26 @@ asmlinkage void post_ttbr_update_workaround(void)
                        CONFIG_CAVIUM_ERRATUM_27456));
 }
 
-static int asids_init(void)
+static int asids_update_limit(void)
 {
-       asid_bits = get_cpu_asid_bits();
+       unsigned long num_available_asids = NUM_USER_ASIDS;
+
+       if (arm64_kernel_unmapped_at_el0())
+               num_available_asids /= 2;
        /*
         * Expect allocation after rollover to fail if we don't have at least
         * one more ASID than CPUs. ASID #0 is reserved for init_mm.
         */
-       WARN_ON(NUM_USER_ASIDS - 1 <= num_possible_cpus());
+       WARN_ON(num_available_asids - 1 <= num_possible_cpus());
+       pr_info("ASID allocator initialised with %lu entries\n",
+               num_available_asids);
+       return 0;
+}
+arch_initcall(asids_update_limit);
+
+static int asids_init(void)
+{
+       asid_bits = get_cpu_asid_bits();
        atomic64_set(&asid_generation, ASID_FIRST_VERSION);
        asid_map = kcalloc(BITS_TO_LONGS(NUM_USER_ASIDS), sizeof(*asid_map),
                           GFP_KERNEL);
@@ -282,8 +294,6 @@ static int asids_init(void)
         */
        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;
 }
 early_initcall(asids_init);