On 2017/7/19 23:07, kbuild test robot wrote:
> Hi Zhen,
>
> [auto build test WARNING on iommu/next]
> [also build test WARNING on v4.13-rc1]
> [if your patch is applied to the wrong git tree, please drop us a note to
> help improve the system]
>
> url:
> https://github.com/0day-ci/linux/commits/Robin-Murphy/Optimise-64-bit-IOVA-allocations/20170719-060847
> base: https://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu.git next
> config: arm-multi_v7_defconfig (attached as .config)
> compiler: arm-linux-gnueabi-gcc (Debian 6.1.1-9) 6.1.1 20160705
> reproduce:
> wget
> https://raw.githubusercontent.com/01org/lkp-tests/master/sbin/make.cross -O
> ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # save the attached .config to linux build tree
> make.cross ARCH=arm
>
> All warnings (new ones prefixed by >>):
>
> drivers/iommu/iova.c: In function 'init_iova_domain':
>>> drivers/iommu/iova.c:53:41: warning: large integer implicitly truncated to
>>> unsigned type [-Woverflow]
> iovad->dma_32bit_pfn = iova_pfn(iovad, 1ULL << 32);
OK, I see. I think the problem is that "1ULL << 32" exceed the scope of 32bits
general register. We should
replace "1ULL << 32" with DMA_BIT_MASK(32), the latter will minus one to keep
it can be safely stored in
the general register.
iovad->dma_32bit_pfn = iova_pfn(iovad, DMA_BIT_MASK(32)) + 1;
> ^~~~
>
> vim +53 drivers/iommu/iova.c
>
> 35
> 36 void
> 37 init_iova_domain(struct iova_domain *iovad, unsigned long
> granule,
> 38 unsigned long start_pfn)
> 39 {
> 40 /*
> 41 * IOVA granularity will normally be equal to the
> smallest
> 42 * supported IOMMU page size; both *must* be capable of
> 43 * representing individual CPU pages exactly.
> 44 */
> 45 BUG_ON((granule > PAGE_SIZE) ||
> !is_power_of_2(granule));
> 46
> 47 spin_lock_init(&iovad->iova_rbtree_lock);
> 48 iovad->rbroot = RB_ROOT;
> 49 iovad->cached_node = NULL;
> 50 iovad->cached32_node = NULL;
> 51 iovad->granule = granule;
> 52 iovad->start_pfn = start_pfn;
> > 53 iovad->dma_32bit_pfn = iova_pfn(iovad, 1ULL << 32);
> 54 init_iova_rcaches(iovad);
> 55 }
> 56 EXPORT_SYMBOL_GPL(init_iova_domain);
> 57
>
> ---
> 0-DAY kernel test infrastructure Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all Intel Corporation
>
--
Thanks!
BestRegards
