Subject: Re: [PATCH v2 1/6] powerpc: prefer memblock APIs returning virtual address

From: Michael Ellerman <[email-masked]>
Date: Tue, 04 Dec 2018 20:59:41 +1100

Hi Mike,

Thanks for trying to clean these up.

I think a few could be improved though ...

Mike Rapoport <[email-masked]> writes:
> diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
> index 913bfca..fa884ad 100644
> --- a/arch/powerpc/kernel/paca.c
> +++ b/arch/powerpc/kernel/paca.c
> @@ -42,17 +42,15 @@ static void *__init alloc_paca_data(unsigned long size, unsigned long align,
>  		nid = early_cpu_to_node(cpu);
>  	}
>  
> -	pa = memblock_alloc_base_nid(size, align, limit, nid, MEMBLOCK_NONE);
> -	if (!pa) {
> -		pa = memblock_alloc_base(size, align, limit);
> -		if (!pa)
> -			panic("cannot allocate paca data");
> -	}
> +	ptr = memblock_alloc_try_nid_raw(size, align, MEMBLOCK_LOW_LIMIT,
> +					 limit, nid);
> +	if (!ptr)
> +		panic("cannot allocate paca data");
  
The old code doesn't zero, but two of the three callers of
alloc_paca_data() *do* zero the whole allocation, so I'd be happy if we
did it in here instead.

That would mean we could use memblock_alloc_try_nid() avoiding the need
to panic() manually.

> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
> index 236c115..d11ee7f 100644
> --- a/arch/powerpc/kernel/setup_64.c
> +++ b/arch/powerpc/kernel/setup_64.c
> @@ -634,19 +634,17 @@ __init u64 ppc64_bolted_size(void)
>  
>  static void *__init alloc_stack(unsigned long limit, int cpu)
>  {
> -	unsigned long pa;
> +	void *ptr;
>  
>  	BUILD_BUG_ON(STACK_INT_FRAME_SIZE % 16);
>  
> -	pa = memblock_alloc_base_nid(THREAD_SIZE, THREAD_SIZE, limit,
> -					early_cpu_to_node(cpu), MEMBLOCK_NONE);
> -	if (!pa) {
> -		pa = memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit);
> -		if (!pa)
> -			panic("cannot allocate stacks");
> -	}
> +	ptr = memblock_alloc_try_nid_raw(THREAD_SIZE, THREAD_SIZE,
> +					 MEMBLOCK_LOW_LIMIT, limit,
> +					 early_cpu_to_node(cpu));
> +	if (!ptr)
> +		panic("cannot allocate stacks");
 
Similarly here, several of the callers zero the stack, and I'd rather
all of them did.

So again we could use memblock_alloc_try_nid() here and remove the
memset()s from emergency_stack_init().

> diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c
> index 9311560..415a1eb0 100644
> --- a/arch/powerpc/mm/pgtable-radix.c
> +++ b/arch/powerpc/mm/pgtable-radix.c
> @@ -51,24 +51,18 @@ static int native_register_process_table(unsigned long base, unsigned long pg_sz
>  static __ref void *early_alloc_pgtable(unsigned long size, int nid,
>  			unsigned long region_start, unsigned long region_end)
>  {
> -	unsigned long pa = 0;
> +	phys_addr_t min_addr = MEMBLOCK_LOW_LIMIT;
> +	phys_addr_t max_addr = MEMBLOCK_ALLOC_ANYWHERE;
>  	void *pt;
>  
> -	if (region_start || region_end) /* has region hint */
> -		pa = memblock_alloc_range(size, size, region_start, region_end,
> -						MEMBLOCK_NONE);
> -	else if (nid != -1) /* has node hint */
> -		pa = memblock_alloc_base_nid(size, size,
> -						MEMBLOCK_ALLOC_ANYWHERE,
> -						nid, MEMBLOCK_NONE);
> +	if (region_start)
> +		min_addr = region_start;
> +	if (region_end)
> +		max_addr = region_end;
>  
> -	if (!pa)
> -		pa = memblock_alloc_base(size, size, MEMBLOCK_ALLOC_ANYWHERE);
> -
> -	BUG_ON(!pa);
> -
> -	pt = __va(pa);
> -	memset(pt, 0, size);
> +	pt = memblock_alloc_try_nid_nopanic(size, size, min_addr, max_addr,
> +					    nid);
> +	BUG_ON(!pt);

I don't think there's any reason to BUG_ON() here rather than letting
memblock() call panic() for us. So this could also be memblock_alloc_try_nid().

> diff --git a/arch/powerpc/platforms/pasemi/iommu.c b/arch/powerpc/platforms/pasemi/iommu.c
> index f297152..f62930f 100644
> --- a/arch/powerpc/platforms/pasemi/iommu.c
> +++ b/arch/powerpc/platforms/pasemi/iommu.c
> @@ -208,7 +208,9 @@ static int __init iob_init(struct device_node *dn)
>  	pr_debug(" -> %s\n", __func__);
>  
>  	/* For 2G space, 8x64 pages (2^21 bytes) is max total l2 size */
> -	iob_l2_base = (u32 *)__va(memblock_alloc_base(1UL<<21, 1UL<<21, 0x80000000));
> +	iob_l2_base = memblock_alloc_try_nid_raw(1UL << 21, 1UL << 21,
> +					MEMBLOCK_LOW_LIMIT, 0x80000000,
> +					NUMA_NO_NODE);

This isn't equivalent is it?

memblock_alloc_base() panics on failure but memblock_alloc_try_nid_raw()
doesn't?

Same comment for the other locations that do that conversion.

cheers