Re: [PATCH] powerpc/mm: Invalidate partition table cache on host proc tbl base update

On Thu, 2017-08-03 at 17:35 +1000, Benjamin Herrenschmidt wrote:

On Thu, 2017-08-03 at 16:30 +1000, Michael Ellerman wrote:

quoted

Suraj Jitindar Singh [off-list ref] writes:

quoted

The host process table base is stored in the partition table by
calling
the function native_register_process_table(). Currently this just
sets
the entry in memory and is missing a proceeding cache
invalidation
instruction. Any update to the partition table should be followed
by a
cache invalidation instruction specifying invalidation of the
caching of
any partition table entries (RIC = 2, PRS = 0).

We already have a function to update the partition table with the
required cache invalidation instructions -
mmu_partition_table_set_entry().
Update the native_register_process_table() function to call
mmu_partition_table_set_entry(), this ensures all appropriate
invalidation will be performed.

Without this patch the kernel will:
 [ ] work normally
 [ ] randomly crash
 [ ] catch fire

I think we get lucky because OPAL added a "flush the whole world" to
opal_reinit_cpus() but this patch seems to improve general code
"correctness".

Cheers,
Ben.

I guess there's the possibility of:
[x] randomly crash

This is required to run a powernv kernel as a guest because we need to
know when it's updated its process table location.