ARC: [mm] Aliasing VIPT dcache support 2/4

This is the meat of the series which prevents any dcache alias creation
by always keeping the U and K mapping of a page congruent.
If a mapping already exists, and other tries to access the page, prev
one is flushed to physical page (wback+inv)

Essentially flush_dcache_page()/copy_user_highpage() create K-mapping
of a page, but try to defer flushing, unless U-mapping exist.
When page is actually mapped to userspace, update_mmu_cache() flushes
the K-mapping (in certain cases this can be optimised out)

Additonally flush_cache_mm(), flush_cache_range(), flush_cache_page()
handle the puring of stale userspace mappings on exit/munmap...

flush_anon_page() handles the existing U-mapping for anon page before
kernel reads it via the GUP path.

Note that while not complete, this is enough to boot a simple
dynamically linked Busybox based rootfs

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 491ae7923b10..5917099470ea 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -182,6 +182,10 @@ config ARC_CACHE_PAGES
           Note that Global I/D ENABLE + Per Page DISABLE works but corollary
           Global DISABLE + Per Page ENABLE won't work
 
+config ARC_CACHE_VIPT_ALIASING
+        bool "Support VIPT Aliasing D$"
+        default n
+
 endif   #ARC_CACHE
 
 config ARC_HAS_ICCM