arm/arm64: Introduce mmu_disable

Allow unit test cpus to disable the MMU. Why not? We want the
test framework to be as flexible as possible. Callers will have
to deal with the cache coherency fallout... Cache flush support
is still forthcoming to the framework though.
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arm/cstart.S

@@ -159,6 +159,15 @@ asm_mmu_enable:
 
 	mov     pc, lr
 
+.globl asm_mmu_disable
+asm_mmu_disable:
+	/* SCTLR */
+	mrc	p15, 0, r0, c1, c0, 0
+	bic	r0, #CR_M
+	mcr	p15, 0, r0, c1, c0, 0
+	isb
+	mov     pc, lr
+
 /*
  * Vector stubs
  * Simplified version of the Linux kernel implementation

arm/cstart64.S

@@ -146,6 +146,14 @@ asm_mmu_enable:
 
 	ret
 
+.globl asm_mmu_disable
+asm_mmu_disable:
+	mrs	x0, sctlr_el1
+	bic	x0, x0, SCTLR_EL1_M
+	msr	sctlr_el1, x0
+	isb
+	ret
+
 /*
  * Vectors
  * Adapted from arch/arm64/kernel/entry.S

lib/arm/asm/mmu-api.h

@@ -4,6 +4,7 @@ extern pgd_t *mmu_idmap;
 extern bool mmu_enabled(void);
 extern void mmu_set_enabled(void);
 extern void mmu_enable(pgd_t *pgtable);
+extern void mmu_disable(void);
 extern void mmu_enable_idmap(void);
 extern void mmu_init_io_sect(pgd_t *pgtable, unsigned long virt_offset);
 extern void mmu_set_range_sect(pgd_t *pgtable, unsigned long virt_offset,

lib/arm/mmu.c

@@ -35,6 +35,14 @@ void mmu_enable(pgd_t *pgtable)
 	mmu_set_enabled();
 }
 
+extern void asm_mmu_disable(void);
+void mmu_disable(void)
+{
+	struct thread_info *ti = current_thread_info();
+	cpumask_clear_cpu(ti->cpu, &mmu_enabled_cpumask);
+	asm_mmu_disable();
+}
+
 void mmu_set_range_ptes(pgd_t *pgtable, unsigned long virt_offset,
 			unsigned long phys_start, unsigned long phys_end,
 			pgprot_t prot)