Re: [PATCH v13 01/12] swiotlb: Refactor swiotlb init functions

[Stefano Stabellini]

On Thu, 17 Jun 2021, Claire Chang wrote:
> Add a new function, swiotlb_init_io_tlb_mem, for the io_tlb_mem struct
> initialization to make the code reusable.
> 
> Signed-off-by: Claire Chang <tientzu@xxxxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Tested-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Tested-by: Will Deacon <will@xxxxxxxxxx>
> ---
>  kernel/dma/swiotlb.c | 50 ++++++++++++++++++++++----------------------
>  1 file changed, 25 insertions(+), 25 deletions(-)
> 
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 52e2ac526757..47bb2a766798 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -168,9 +168,28 @@ void __init swiotlb_update_mem_attributes(void)
>  	memset(vaddr, 0, bytes);
>  }
>  
> -int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
> +static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
> +				    unsigned long nslabs, bool late_alloc)
>  {
> +	void *vaddr = phys_to_virt(start);
>  	unsigned long bytes = nslabs << IO_TLB_SHIFT, i;
> +
> +	mem->nslabs = nslabs;
> +	mem->start = start;
> +	mem->end = mem->start + bytes;
> +	mem->index = 0;
> +	mem->late_alloc = late_alloc;
> +	spin_lock_init(&mem->lock);
> +	for (i = 0; i < mem->nslabs; i++) {
> +		mem->slots[i].list = IO_TLB_SEGSIZE - io_tlb_offset(i);
> +		mem->slots[i].orig_addr = INVALID_PHYS_ADDR;
> +		mem->slots[i].alloc_size = 0;
> +	}
> +	memset(vaddr, 0, bytes);
> +}
> +
> +int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
> +{
>  	struct io_tlb_mem *mem;
>  	size_t alloc_size;
>  
> @@ -186,16 +205,8 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
>  	if (!mem)
>  		panic("%s: Failed to allocate %zu bytes align=0x%lx\n",
>  		      __func__, alloc_size, PAGE_SIZE);
> -	mem->nslabs = nslabs;
> -	mem->start = __pa(tlb);
> -	mem->end = mem->start + bytes;
> -	mem->index = 0;
> -	spin_lock_init(&mem->lock);
> -	for (i = 0; i < mem->nslabs; i++) {
> -		mem->slots[i].list = IO_TLB_SEGSIZE - io_tlb_offset(i);
> -		mem->slots[i].orig_addr = INVALID_PHYS_ADDR;
> -		mem->slots[i].alloc_size = 0;
> -	}
> +
> +	swiotlb_init_io_tlb_mem(mem, __pa(tlb), nslabs, false);
>  
>  	io_tlb_default_mem = mem;
>  	if (verbose)
> @@ -282,8 +293,8 @@ swiotlb_late_init_with_default_size(size_t default_size)
>  int
>  swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
>  {
> -	unsigned long bytes = nslabs << IO_TLB_SHIFT, i;
>  	struct io_tlb_mem *mem;
> +	unsigned long bytes = nslabs << IO_TLB_SHIFT;
>  
>  	if (swiotlb_force == SWIOTLB_NO_FORCE)
>  		return 0;
> @@ -297,20 +308,9 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
>  	if (!mem)
>  		return -ENOMEM;
>  
> -	mem->nslabs = nslabs;
> -	mem->start = virt_to_phys(tlb);
> -	mem->end = mem->start + bytes;
> -	mem->index = 0;
> -	mem->late_alloc = 1;
> -	spin_lock_init(&mem->lock);
> -	for (i = 0; i < mem->nslabs; i++) {
> -		mem->slots[i].list = IO_TLB_SEGSIZE - io_tlb_offset(i);
> -		mem->slots[i].orig_addr = INVALID_PHYS_ADDR;
> -		mem->slots[i].alloc_size = 0;
> -	}
> -
> +	memset(mem, 0, sizeof(*mem));
> +	swiotlb_init_io_tlb_mem(mem, virt_to_phys(tlb), nslabs, true);
>  	set_memory_decrypted((unsigned long)tlb, bytes >> PAGE_SHIFT);
> -	memset(tlb, 0, bytes);
 
This is good for swiotlb_late_init_with_tbl. However I have just noticed
that mem could also be allocated from swiotlb_init_with_tbl, in which
case the zeroing is missing. I think we need another memset in
swiotlb_init_with_tbl as well. Or maybe it could be better to have a
single memset at the beginning of swiotlb_init_io_tlb_mem instead. Up to
you.