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Date: Tue, 1 Feb 2011 16:18:59 -0500 From: Chuck Ebbert <cebbert@...hat.com> To: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp> Cc: hancockrwd@...il.com, ak@...ux.intel.com, linux-kernel@...r.kernel.org, dwmw2@...radead.org Subject: Re: b44 driver causes panic when using swiotlb On Tue, 1 Feb 2011 10:28:00 +0900 FUJITA Tomonori <fujita.tomonori@....ntt.co.jp> wrote: > > swiotlb allocates the bounce buffer when a system boots up. We can't > allocate much in GFP_DMA. swiotlb uses somewhere under 4GB. So it > can't help devices that have odd dma_mask (that is, except for 4GB). > > Unfortunately, Such device needs to do own custom bouncing or needs > their subsystem to does that. I think we're chasing the wrong problem here. swiotlb uses alloc_bootmem_low_pages() to try to get buffers as low in memory as possible. I asked someone who is hitting this bug to try 2.6.36 and he reports the buffers really are low there: 2.6.36: 5c00000 2.6.37: db600000 So something happened very early in the 2.6.37-rc cycle that changed this behavior. I tried looking at the bootmem code but could not see the problem. The only related option I could find in .config was this: # CONFIG_NO_BOOTMEM is not set It was set this way in both .36 and .37. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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