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Mismatched attributes

The cache models perform the following checks for mismatched attributes:


  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.


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/p Privileged/Non-privileged.
N/S Non-secure/Secure.
I/D Instruction-side access/Data-side access.
u0x0/m0x2 Corresponds to the internal concepts of user flags and AXI IDs of the model.
ish/osh/nsh/sys Inner shareable/Outer shareable/Non-shareable/System.
ra Read-allocate.
wa Write-allocate.
C Cacheable.
NC Non-Cacheable to normal memory.
SO Strongly-Ordered memory.
DV DeVice 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/sys Inner shareable/Outer shareable/Non-shareable/System.
iHittable The inner cacheability marks it as hittable in this cache.
oHittable The 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.