[U-Boot] [PATCH v1 13/15] efi_loader: make pool allocations cacheline aligned

[Rob Clark]

On Fri, Aug 11, 2017 at 12:58 PM, Heinrich Schuchardt
<xypron.glpk at gmx.de> wrote:
> On 08/10/2017 08:29 PM, Rob Clark wrote:
>> This avoids printf() spam about file reads (such as loading an image)
>> into unaligned buffers (and the associated memcpy()).  And generally
>> seems like a good idea.
>>
>> Signed-off-by: Rob Clark <robdclark at gmail.com>
>> ---
>>  lib/efi_loader/efi_memory.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c
>> index 9e079f1fa3..2ba8d8b42b 100644
>> --- a/lib/efi_loader/efi_memory.c
>> +++ b/lib/efi_loader/efi_memory.c
>> @@ -43,7 +43,7 @@ void *efi_bounce_buffer;
>>   */
>>  struct efi_pool_allocation {
>>       u64 num_pages;
>> -     char data[];
>> +     char data[] __attribute__((aligned(ARCH_DMA_MINALIGN)));
>>  };
>>
>>  /*
>> @@ -356,7 +356,8 @@ efi_status_t efi_allocate_pool(int pool_type, unsigned long size,
>>  {
>>       efi_status_t r;
>>       efi_physical_addr_t t;
>> -     u64 num_pages = (size + sizeof(u64) + EFI_PAGE_MASK) >> EFI_PAGE_SHIFT;
>> +     u64 num_pages = DIV_ROUND_UP(size + sizeof(struct efi_pool_allocation),
>> +                                  EFI_PAGE_SIZE);
>
> It seems you missed my mail dated 2017-08-02T01:21Z:
>
> With DIV_ROUND_UP you introduce a 64bit division. Depending on the
> architecture this is only available via stdlib which is not available in
> U-Boot.
>
> Please, use
> + EFI_PAGE_MASK) >> EFI_PAGE_SHIFT;
> as in the original line.
>

I didn't miss it.. but I did disagree with it.  It is an unsigned
division by a power-of-two.  The compiler turns this into a
right-shift.  So in fact both ways generate the same code, but the
DIV_ROUND_UP() is more clear.

BR,
-R