[Skiboot] [PATCH skiboot] npu2: Reset PID wildcard and refcounter when mapped to LPID

[Stewart Smith]

Alexey Kardashevskiy <aik at ozlabs.ru> writes:
> Since 105d80f85b "npu2: Use unfiltered mode in XTS tables" we do not
> register every PID in the XTS table so the table has one entry per LPID.
> Then we added a reference counter to keep track of the entry use when
> switching GPU between the host and guest systems (the "Fixes:" tag below).
>
> The POWERNV platform setup creates such entries and references them
> at the boot time when initializing IOMMUs and only removes it when
> a GPU is passed through to a guest. This creates a problem as POWERNV
> boots via kexec and no defererencing happens; the XTS table state remains
> undefined. So when the host kernel boots, skiboot thinks there are valid
> XTS entries and does not update the XTS table which breaks ATS.
>
> This adds the reference counter and the XTS entry reset when a GPU is
> assigned to LPID and we cannot rely on the kernel to clean that up.
>
> Fixes: ba1d95a1d460 ("npu2: Add XTS_BDF_MAP wildcard refcount")
> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
> ---
>
> Fix for: https://bugzilla.linux.ibm.com/show_bug.cgi?id=177182

Merged to master as of 7c977c734e1c4d3be9a036a075798530d352d8e3

-- 
Stewart Smith
OPAL Architect, IBM.