arm64: mm: Allocate ASIDs in pairs

In preparation for separate kernel/user ASIDs, allocate them in pairs
for each mm_struct. The bottom bit distinguishes the two: if it is set,
then the ASID will map only userspace.

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>

diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 0d34bf0..01bfb18 100644 (file)
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -17,6 +17,7 @@
 #define __ASM_MMU_H
 
 #define MMCF_AARCH32   0x1     /* mm context flag for AArch32 executables */
+#define USER_ASID_FLAG (UL(1) << 48)
 
 typedef struct {
        atomic64_t      id;

diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
index 78a2dc5..1cb3bc9 100644 (file)
--- a/arch/arm64/mm/context.c
+++ b/arch/arm64/mm/context.c
@@ -39,7 +39,16 @@ static cpumask_t tlb_flush_pending;
 
 #define ASID_MASK              (~GENMASK(asid_bits - 1, 0))
 #define ASID_FIRST_VERSION     (1UL << asid_bits)
-#define NUM_USER_ASIDS         ASID_FIRST_VERSION
+
+#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
+#define NUM_USER_ASIDS         (ASID_FIRST_VERSION >> 1)
+#define asid2idx(asid)         (((asid) & ~ASID_MASK) >> 1)
+#define idx2asid(idx)          (((idx) << 1) & ~ASID_MASK)
+#else
+#define NUM_USER_ASIDS         (ASID_FIRST_VERSION)
+#define asid2idx(asid)         ((asid) & ~ASID_MASK)
+#define idx2asid(idx)          asid2idx(idx)
+#endif
 
 /* Get the ASIDBits supported by the current CPU */
 static u32 get_cpu_asid_bits(void)
@@ -98,7 +107,7 @@ static void flush_context(unsigned int cpu)
                 */
                if (asid == 0)
                        asid = per_cpu(reserved_asids, i);
-               __set_bit(asid & ~ASID_MASK, asid_map);
+               __set_bit(asid2idx(asid), asid_map);
                per_cpu(reserved_asids, i) = asid;
        }
 
@@ -153,16 +162,16 @@ static u64 new_context(struct mm_struct *mm, unsigned int cpu)
                 * We had a valid ASID in a previous life, so try to re-use
                 * it if possible.
                 */
-               asid &= ~ASID_MASK;
-               if (!__test_and_set_bit(asid, asid_map))
+               if (!__test_and_set_bit(asid2idx(asid), asid_map))
                        return newasid;
        }
 
        /*
         * Allocate a free ASID. If we can't find one, take a note of the
-        * currently active ASIDs and mark the TLBs as requiring flushes.
-        * We always count from ASID #1, as we use ASID #0 when setting a
-        * reserved TTBR0 for the init_mm.
+        * currently active ASIDs and mark the TLBs as requiring flushes.  We
+        * always count from ASID #2 (index 1), as we use ASID #0 when setting
+        * a reserved TTBR0 for the init_mm and we allocate ASIDs in even/odd
+        * pairs.
         */
        asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, cur_idx);
        if (asid != NUM_USER_ASIDS)
@@ -179,7 +188,7 @@ static u64 new_context(struct mm_struct *mm, unsigned int cpu)
 set_asid:
        __set_bit(asid, asid_map);
        cur_idx = asid;
-       return asid | generation;
+       return idx2asid(asid) | generation;
 }
 
 void check_and_switch_context(struct mm_struct *mm, unsigned int cpu)