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Subject[PATCH 03/29] arm64: mm: Allocate ASIDs in pairs
Date
From: Will Deacon <will.deacon@arm.com>

commit 0c8ea531b774 upstream.

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>
Signed-off-by: Alex Shi <alex.shi@linaro.org>

Conflicts:
no MMCF_AARCH32 in arch/arm64/include/asm/mmu.h
---
arch/arm64/include/asm/mmu.h | 2 ++
arch/arm64/mm/context.c | 25 +++++++++++++++++--------
2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 8d9fce0..49924e5 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -16,6 +16,8 @@
#ifndef __ASM_MMU_H
#define __ASM_MMU_H

+#define USER_ASID_FLAG (UL(1) << 48)
+
typedef struct {
atomic64_t id;
void *vdso;
diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
index efcf1f7..f00f5ee 100644
--- 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)
@@ -104,7 +113,7 @@ 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;
}

@@ -159,16 +168,16 @@ 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)
@@ -185,7 +194,7 @@ 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)
--
2.7.4
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