powerpc/powernv/memtrace: Let the arch hotunplug code flush cache

[ Upstream commit 7fd6641d ]

Don't do this via custom code, instead now that we have support in the
arch hotplug/hotunplug code, rely on those routines to do the right
thing.

The existing flush doesn't work because it uses ppc64_caches.l1d.size
instead of ppc64_caches.l1d.line_size.

Fixes: 9d5171a8 ("powerpc/powernv: Enable removal of memory for in memory tracing")
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Reviewed-by: Rashmica Gupta <rashmica.g@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/powerpc/platforms/powernv/memtrace.c

@@ -82,19 +82,6 @@ static const struct file_operations memtrace_fops = {
 	.open	= simple_open,
 };
 
-static void flush_memory_region(u64 base, u64 size)
-{
-	unsigned long line_size = ppc64_caches.l1d.size;
-	u64 end = base + size;
-	u64 addr;
-
-	base = round_down(base, line_size);
-	end = round_up(end, line_size);
-
-	for (addr = base; addr < end; addr += line_size)
-		asm volatile("dcbf 0,%0" : "=r" (addr) :: "memory");
-}
-
 static int check_memblock_online(struct memory_block *mem, void *arg)
 {
 	if (mem->state != MEM_ONLINE)
@@ -132,10 +119,6 @@ static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages)
 	walk_memory_range(start_pfn, end_pfn, (void *)MEM_OFFLINE,
 			  change_memblock_state);
 
-	/* RCU grace period? */
-	flush_memory_region((u64)__va(start_pfn << PAGE_SHIFT),
-			    nr_pages << PAGE_SHIFT);
-
 	lock_device_hotplug();
 	remove_memory(nid, start_pfn << PAGE_SHIFT, nr_pages << PAGE_SHIFT);
 	unlock_device_hotplug();