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Mismatched attributes

The cache models perform the following checks for mismatched attributes:

Cause

  1. A 4KiB page is accessed for the first time and the system checks whether any lines from that region exist in the cache. If they mismatch, the system issues a warning.
  2. A cacheable access hits in the cache, but the cache line was fetched with different attributes.
  3. A snoop request is received that hits a cache line that has it marked as non-shared.

Reason

It is UNPREDICTABLE in the architecture if shareability or cacheability are mixed. You must follow an appropriate sequence of cache maintenance and Translation Lookaside Buffer (TLB) operations to change the attributes.

Example 1

FVP_VE_Cortex_A15x4_Cortex_A7x4.coretile.cluster0.cluster0.l2_cache: Mismatch in attributes for page including address ns-000000008ff03000
    29 cache lines are allocated with attributes:-
        inner-WB-cacheable outer-WB-cacheable shareability: osh
    but transaction attributes are:-
        inner-WB-cacheable outer-WB-cacheable shareability: ish
         (PNI-u0x0-m0x2-ish-rawaC-rawaC) inner-WB-cacheable Inner cacheable write back (WB)
          outer-WB-cacheable Outer cacheable write back (WB)

PNI-u0x0-m0x2-ish-rawaC-rawaC is interpreted as follows:

P/pPrivileged/Non-privileged.
N/SNon-secure/Secure.
I/DInstruction-side access/Data-side access.
u0x0/m0x2Corresponds to the internal concepts of user flags and AXI IDs of the model.
ish/osh/nsh/sysInner shareable/Outer shareable/Non-shareable/System.
raRead-allocate.
waWrite-allocate.
CCacheable.
NCNon-Cacheable to normal memory.
SOStrongly-Ordered memory.
DVDeVice memory.

Example 2

cluster0.l1icache_2-entry177: Mismatch in transaction from upstream port0 and an existing entry in the cache:
    Mismatch between cache entry ns-000000008ff05600-osh-iHittable-oHittable
                 and transaction ns-000000008ff05600-ish-iHittable-oHittable
ns/s Non-secure/Secure.
000000008ff05600 The physical address.
ish/osh/nsh/sysInner shareable/Outer shareable/Non-shareable/System.
iHittableThe inner cacheability marks it as hittable in this cache.
oHittableThe outer cacheability marks it as hittable in this cache.

Example 3

<name>-entry177: Received a snoop request for [<address-range>]
and we hit an existing entry in the cache but it was incompatible with
being the response to a snoop request:
    <mis-match message>
We are suppressing the hit in the cache, but a specific implementation
may or may not do the same thing.
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