Hi Michal and Michael,

On 02/15/2018 05:13 AM, Michal Suchánek wrote:
From: Michael Ellerman<m...@ellerman.id.au>

For PowerVM migration we want to be able to call setup_rfi_flush()
again after we've migrated the partition.

To support that we need to check that we're not trying to allocate the
fallback flush area after memblock has gone away. If so we just fail,
we don't support migrating from a patched to an unpatched machine. Or
we do support it, but there will be no RFI flush enabled on the
destination.

This sounds bad to me. Either we support RFI flush or we don't.

If we do the fallback area should be allocated at boot so it is always
available. [snip]

I think the problem with this is the size of the fallback area might
have to be different between the origin and destination systems, say,
a larger L1 data cache at the destination.

In that case, the original size might not be enough to fully flush
the L1 data cache.

Michael, is that the reason it is done that way?  I thought of that,
but don't know for sure.

Thanks!
Mauricio

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