There's no reason why this shouldn't work and it doesn't smell like a hardware problem.
The problem is solved !
The reason was that shared memory on host have been allocated using __get_free_pages(GFP_KERNEL, get_order(NumberOfBytes))
it returned addresses like 0x8xxxxxxx (KSEG0, cacheable)
I was adviced to use pci_alloc_consistent() instead , this function uses __get_free_pages
but sets some GFP flags and returns addresses like 0xAxxxxxxx (KSEG1).
With this function all works fine !
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