Messages in this thread | | | From | Eli Cohen <> | Subject | RE: [linux-next PATCH] mlx5: wrong page mask if CONFIG_ARCH_DMA_ADDR_T_64BIT enabled for 32Bit architectures | Date | Mon, 13 Apr 2015 06:47:11 +0000 |
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On Mon, Apr 13, 2015 at 08:33:33AM +0800, Honggang LI wrote: > > Yes, replaced all of the PAGE_MASK in the file. Please see attched new > patch. >
I think you need to send the new patch inline in your email.
> > > > @@ -241,7 +243,7 @@ static void free_4k(struct mlx5_core_dev *dev, u64 addr) static int alloc_system_page(struct mlx5_core_dev *dev, u16 func_id) { > > struct page *page; > > - u64 addr; > > + u64 addr = 0; [Eli] Why is this required? > > For 32bit architectures, if CONFIG_ARCH_DMA_ADDR_T_64BIT disabled and > physical memory is less than 4GB, dma_map_page will return an u32 integer > less than 0xffff_ffff. And if addr had been initialized with random > rubbish in the stack of alloc_system_page, the high four bytes is > unpredictable. The new mask, MLX5_NUM_4K_IN_PAGE, will reserve the high > four bytes. So, free_4k/find_fw_page will randomly failed. >
Sorry, I still don't understand the issue here. MLX5_NUM_4K_IN_PAGE is not a mask and will always get the correct value which is fairly small.
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