arm64: KVM: Invoke compute_layout() before alternatives are applied

compute_layout() is invoked as part of an alternative fixup under
stop_machine(). This function invokes get_random_long() which acquires a
sleeping lock on -RT which can not be acquired in this context.

Rename compute_layout() to kvm_compute_layout() and invoke it before
stop_machine() applies the alternatives. Add a __init prefix to
kvm_compute_layout() because the caller has it, too (and so the code can be
discarded after boot).
Reviewed-by: James Morse <james.morse@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/kvm_mmu.h

@@ -91,6 +91,7 @@ alternative_cb_end
 
 void kvm_update_va_mask(struct alt_instr *alt,
 			__le32 *origptr, __le32 *updptr, int nr_inst);
+void kvm_compute_layout(void);
 
 static inline unsigned long __kern_hyp_va(unsigned long v)
 {

arch/arm64/kernel/smp.c

@@ -31,6 +31,7 @@
 #include <linux/of.h>
 #include <linux/irq_work.h>
 #include <linux/kexec.h>
+#include <linux/kvm_host.h>
 
 #include <asm/alternative.h>
 #include <asm/atomic.h>
@@ -39,6 +40,7 @@
 #include <asm/cputype.h>
 #include <asm/cpu_ops.h>
 #include <asm/daifflags.h>
+#include <asm/kvm_mmu.h>
 #include <asm/mmu_context.h>
 #include <asm/numa.h>
 #include <asm/pgtable.h>
@@ -408,6 +410,8 @@ static void __init hyp_mode_check(void)
 			   "CPU: CPUs started in inconsistent modes");
 	else
 		pr_info("CPU: All CPU(s) started at EL1\n");
+	if (IS_ENABLED(CONFIG_KVM_ARM_HOST))
+		kvm_compute_layout();
 }
 
 void __init smp_cpus_done(unsigned int max_cpus)

arch/arm64/kvm/va_layout.c

@@ -22,7 +22,7 @@ static u8 tag_lsb;
 static u64 tag_val;
 static u64 va_mask;
 
-static void compute_layout(void)
+__init void kvm_compute_layout(void)
 {
 	phys_addr_t idmap_addr = __pa_symbol(__hyp_idmap_text_start);
 	u64 hyp_va_msb;
@@ -110,9 +110,6 @@ void __init kvm_update_va_mask(struct alt_instr *alt,
 
 	BUG_ON(nr_inst != 5);
 
-	if (!has_vhe() && !va_mask)
-		compute_layout();
-
 	for (i = 0; i < nr_inst; i++) {
 		u32 rd, rn, insn, oinsn;
 
@@ -156,9 +153,6 @@ void kvm_patch_vector_branch(struct alt_instr *alt,
 		return;
 	}
 
-	if (!va_mask)
-		compute_layout();
-
 	/*
 	 * Compute HYP VA by using the same computation as kern_hyp_va()
 	 */