[PATCH 2/2] powerpc/mm/memtrace: Let the arch hotunplug code flush cache

[Michael Ellerman]

Balbir Singh <bsingharora at gmail.com> writes:

> 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.
>
> Fixes: 9d5171a8f248 ("powerpc/powernv: Enable removal of memory for in memory tracing")

That's not really right.

This patch doesn't fix it, the previous patch did.

If I just backport this patch then it's still broken.

So I'll tag patch 1 with the above Fixes: tag and add stable, and then
this just becomes a cleanup.

OK?

cheers

> diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c
> index de470caf0784..fc222a0c2ac4 100644
> --- a/arch/powerpc/platforms/powernv/memtrace.c
> +++ b/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();
> -- 
> 2.13.6