powerpc/64s: do not re-activate batched TLB flush

Patch series "Nesting support for lazy MMU mode", v6.

When the lazy MMU mode was introduced eons ago, it wasn't made clear
whether such a sequence was legal:

arch_enter_lazy_mmu_mode()
...
arch_enter_lazy_mmu_mode()
...
arch_leave_lazy_mmu_mode()
...
arch_leave_lazy_mmu_mode()

It seems fair to say that nested calls to
arch_{enter,leave}_lazy_mmu_mode() were not expected, and most
architectures never explicitly supported it.

Nesting does in fact occur in certain configurations, and avoiding it has
proved difficult. This series therefore enables lazy_mmu sections to
nest, on all architectures.

Nesting is handled using a counter in task_struct (patch 8), like other
stateless APIs such as pagefault_{disable,enable}(). This is fully
handled in a new generic layer in <linux/pgtable.h>; the arch_* API
remains unchanged. A new pair of calls, lazy_mmu_mode_{pause,resume}(),
is also introduced to allow functions that are called with the lazy MMU
mode enabled to temporarily pause it, regardless of nesting.

An arch now opts in to using the lazy MMU mode by selecting
CONFIG_ARCH_LAZY_MMU; this is more appropriate now that we have a generic
API, especially with state conditionally added to task_struct.


This patch (of 14):

Since commit b9ef323ea168 ("powerpc/64s: Disable preemption in hash lazy
mmu mode") a task can not be preempted while in lazy MMU mode. Therefore,
the batch re-activation code is never called, so remove it.

Link: https://lkml.kernel.org/r/20251215150323.2218608-1-kevin.brodsky@arm.com
Link: https://lkml.kernel.org/r/20251215150323.2218608-2-kevin.brodsky@arm.com
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David S. Miller <davem@davemloft.net>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Juegren Gross <jgross@suse.com>
Cc: levi.yun <yeoreum.yun@arm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: David Hildenbrand (Red Hat) <david@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>