mainline inclusion
from mainline-4.21
commit: 3d65b6bbc01ecece8142e62a8a5f1d48ba41a240
category: feature
feature: Reduce synchronous TLB invalidation on ARM64
bugzilla: NA
CVE: NA

--------------------------------------------------

In order to reduce the possibility of soft lock-ups, we bound the
maximum number of TLBI operations performed by a single call to
flush_tlb_range() to an arbitrary constant of 1024.

Whilst this does the job of avoiding lock-ups, we can actually be a bit
smarter by defining this as PTRS_PER_PTE. Due to the structure of our
page tables, using PTRS_PER_PTE means that an outer loop calling
flush_tlb_range() for entire table entries will end up performing just a
single TLBI operation for each entry. As an example, mremap()ing a 1GB
range mapped using 4k pages now requires only 512 TLBI operations when
moving the page tables as opposed to 262144 operations (512*512) when
using the current threshold of 1024.

Cc: Joel Fernandes <joel@joelfernandes.org>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NHanjun Guo <guohanjun@huawei.com>
Reviewed-by: NXuefeng Wang <wxf.wang@hisilicon.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>