FROMLIST: arm64: mm: Add arm64_kernel_unmapped_at_el0 helper

In order for code such as TLB invalidation to operate efficiently when
the decision to map the kernel at EL0 is determined at runtime, this
patch introduces a helper function, arm64_kernel_unmapped_at_el0, to
determine whether or not the kernel is mapped whilst running in userspace.

Currently, this just reports the value of CONFIG_UNMAP_KERNEL_AT_EL0,
but will later be hooked up to a fake CPU capability using a static key.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Tested-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
(cherry picked from git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git
 commit fc0e1299da548b32440051f58f08e0c1eb7edd0b)

Change-Id: I0f48eadf55ee97f09553380a62d9fffe54d9dc83
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index be814d4..8e60392 100644 (file)
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -18,6 +18,8 @@
 
 #define USER_ASID_FLAG (UL(1) << 48)
 
+#ifndef __ASSEMBLY__
+
 typedef struct {
        atomic64_t      id;
        void            *vdso;
@@ -30,6 +32,11 @@ typedef struct {
  */
 #define ASID(mm)       ((mm)->context.id.counter & 0xffff)
 
+static inline bool arm64_kernel_unmapped_at_el0(void)
+{
+       return IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0);
+}
+
 extern void paging_init(void);
 extern void __iomem *early_io_map(phys_addr_t phys, unsigned long virt);
 extern void init_mem_pgprot(void);
@@ -38,4 +45,5 @@ extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
                               pgprot_t prot);
 extern void *fixmap_remap_fdt(phys_addr_t dt_phys);
 
+#endif /* !__ASSEMBLY__ */
 #endif