4.9-stable review patch.  If anyone has any objections, please let me know.


From: Will Deacon <will.dea...@arm.com>

commit fc0e1299da54 upstream.

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.rutl...@arm.com>
Tested-by: Laura Abbott <labb...@redhat.com>
Tested-by: Shanker Donthineni <shank...@codeaurora.org>
Signed-off-by: Will Deacon <will.dea...@arm.com>
Signed-off-by: Alex Shi <alex....@linaro.org> [v4.9 backport]
Signed-off-by: Mark Rutland <mark.rutl...@arm.com> [v4.9 backport]
Tested-by: Will Deacon <will.dea...@arm.com>
Tested-by: Greg Hackmann <ghackm...@google.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
 arch/arm64/include/asm/mmu.h |    8 ++++++++
 1 file changed, 8 insertions(+)

--- 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)
 extern void paging_init(void);
 extern void bootmem_init(void);
 extern void __iomem *early_io_map(phys_addr_t phys, unsigned long virt);
@@ -39,4 +46,5 @@ extern void create_pgd_mapping(struct mm
                               pgprot_t prot, bool allow_block_mappings);
 extern void *fixmap_remap_fdt(phys_addr_t dt_phys);
+#endif /* !__ASSEMBLY__ */

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