target/arm: Add helper_mte_check_zva

Use a special helper for DC_ZVA, rather than the more
general mte_checkN.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200626033144.790098-28-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 106 insertions, 0 deletions

diff --git a/target/arm/mte_helper.c b/target/arm/mte_helper.c
index abe6af6b79..4f9bd3add3 100644
--- a/target/arm/mte_helper.c
+++ b/target/arm/mte_helper.c
@@ -667,3 +667,109 @@ uint64_t HELPER(mte_checkN)(CPUARMState *env, uint32_t desc, uint64_t ptr)
 {
     return mte_checkN(env, desc, ptr, GETPC());
 }
+
+/*
+ * Perform an MTE checked access for DC_ZVA.
+ */
+uint64_t HELPER(mte_check_zva)(CPUARMState *env, uint32_t desc, uint64_t ptr)
+{
+    uintptr_t ra = GETPC();
+    int log2_dcz_bytes, log2_tag_bytes;
+    int mmu_idx, bit55;
+    intptr_t dcz_bytes, tag_bytes, i;
+    void *mem;
+    uint64_t ptr_tag, mem_tag, align_ptr;
+
+    bit55 = extract64(ptr, 55, 1);
+
+    /* If TBI is disabled, the access is unchecked, and ptr is not dirty. */
+    if (unlikely(!tbi_check(desc, bit55))) {
+        return ptr;
+    }
+
+    ptr_tag = allocation_tag_from_addr(ptr);
+
+    if (tcma_check(desc, bit55, ptr_tag)) {
+        goto done;
+    }
+
+    /*
+     * In arm_cpu_realizefn, we asserted that dcz > LOG2_TAG_GRANULE+1,
+     * i.e. 32 bytes, which is an unreasonably small dcz anyway, to make
+     * sure that we can access one complete tag byte here.
+     */
+    log2_dcz_bytes = env_archcpu(env)->dcz_blocksize + 2;
+    log2_tag_bytes = log2_dcz_bytes - (LOG2_TAG_GRANULE + 1);
+    dcz_bytes = (intptr_t)1 << log2_dcz_bytes;
+    tag_bytes = (intptr_t)1 << log2_tag_bytes;
+    align_ptr = ptr & -dcz_bytes;
+
+    /*
+     * Trap if accessing an invalid page.  DC_ZVA requires that we supply
+     * the original pointer for an invalid page.  But watchpoints require
+     * that we probe the actual space.  So do both.
+     */
+    mmu_idx = FIELD_EX32(desc, MTEDESC, MIDX);
+    (void) probe_write(env, ptr, 1, mmu_idx, ra);
+    mem = allocation_tag_mem(env, mmu_idx, align_ptr, MMU_DATA_STORE,
+                             dcz_bytes, MMU_DATA_LOAD, tag_bytes, ra);
+    if (!mem) {
+        goto done;
+    }
+
+    /*
+     * Unlike the reasoning for checkN, DC_ZVA is always aligned, and thus
+     * it is quite easy to perform all of the comparisons at once without
+     * any extra masking.
+     *
+     * The most common zva block size is 64; some of the thunderx cpus use
+     * a block size of 128.  For user-only, aarch64_max_initfn will set the
+     * block size to 512.  Fill out the other cases for future-proofing.
+     *
+     * In order to be able to find the first miscompare later, we want the
+     * tag bytes to be in little-endian order.
+     */
+    switch (log2_tag_bytes) {
+    case 0: /* zva_blocksize 32 */
+        mem_tag = *(uint8_t *)mem;
+        ptr_tag *= 0x11u;
+        break;
+    case 1: /* zva_blocksize 64 */
+        mem_tag = cpu_to_le16(*(uint16_t *)mem);
+        ptr_tag *= 0x1111u;
+        break;
+    case 2: /* zva_blocksize 128 */
+        mem_tag = cpu_to_le32(*(uint32_t *)mem);
+        ptr_tag *= 0x11111111u;
+        break;
+    case 3: /* zva_blocksize 256 */
+        mem_tag = cpu_to_le64(*(uint64_t *)mem);
+        ptr_tag *= 0x1111111111111111ull;
+        break;
+
+    default: /* zva_blocksize 512, 1024, 2048 */
+        ptr_tag *= 0x1111111111111111ull;
+        i = 0;
+        do {
+            mem_tag = cpu_to_le64(*(uint64_t *)(mem + i));
+            if (unlikely(mem_tag != ptr_tag)) {
+                goto fail;
+            }
+            i += 8;
+            align_ptr += 16 * TAG_GRANULE;
+        } while (i < tag_bytes);
+        goto done;
+    }
+
+    if (likely(mem_tag == ptr_tag)) {
+        goto done;
+    }
+
+ fail:
+    /* Locate the first nibble that differs. */
+    i = ctz64(mem_tag ^ ptr_tag) >> 4;
+    mte_check_fail(env, mmu_idx, align_ptr + i * TAG_GRANULE, ra);
+
+ done:
+    return useronly_clean_ptr(ptr);
+}