Messages in this thread Patch in this message | | | Date | Wed, 22 Oct 2008 13:07:53 +0200 | From | Takashi Iwai <> | Subject | Re: swiotlb_alloc_coherent: allocated memory is out of range for device |
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At Wed, 22 Oct 2008 12:53:58 +0200, I wrote: > > At Sun, 19 Oct 2008 12:09:32 +0200, > Sven Schnelle wrote: > > > > Hi List, > > > > my kernel dies while probing parport with the following last words: > > > > [ 3.672199] parport_pc 00:0b: reported by Plug and Play ACPI > > [ 3.677969] parport0: PC-style at 0x378 (0x778), irq 7, dma 3 [PCSPP,TRISTATE,COMPAT,EPP,ECP,DMA] > > [ 3.687691] hwdev DMA mask = 0x0000000000ffffff, dev_addr = 0x0000000020000000 > > [ 3.694916] Kernel panic - not syncing: swiotlb_alloc_coherent: allocated memory is out of range for device > > > > I haven't started a bisection yet, but this seems to be introduced > > somewhere between 2.6.26 and 2.6.27, at least 2.6.26 was working without > > problems. The dmesg log + config was obtained from a kernel compiled > > from git on 10/16/2008. > > This bug hits me, too. Looks like swiotlb assumes that the alloc caller > must set GFP_DMA appropriately by itself since GFP_DMA hack was > removed. The patch below should fix this particular case. > > HOWEVER: the fundamental problem appears to be in swiotlb itself. > It assumes that iotlb pages are in DMA area. But, in this case, the > driver sets 24bit DMA (as of PnP) while iotlb pages are allocated > under 32bit DMA via alloc_bootmem_low_pages(). This doesn't work, of > course. > > So, even adding GFP_DMA works mostly, it has still potentially > breakage when you can't get the page and fall back to iotlb pages, > just like the panic above. > > Also, the removal of GFP_DMA hack is a bad idea. For example, if a > device requires 28bit DMA mask, it doesn't set always GFP_DMA for > allocation because pages in ZONE_NORMAL may be inside that DMA mask. > Normal allocators allow this behavior but swiotlb allocator doesn't. > (Correct me if I'm wrong here -- I haven't followed much the recent > changes.)
The patch below is to a workaround for that.
Takashi
diff --git a/lib/swiotlb.c b/lib/swiotlb.c index f8eebd4..cb20149 100644 --- a/lib/swiotlb.c +++ b/lib/swiotlb.c @@ -468,6 +468,7 @@ swiotlb_alloc_coherent(struct device *hwdev, size_t size, void *ret; int order = get_order(size); + again: ret = (void *)__get_free_pages(flags, order); if (ret && address_needs_mapping(hwdev, virt_to_bus(ret), size)) { /* @@ -478,6 +479,10 @@ swiotlb_alloc_coherent(struct device *hwdev, size_t size, ret = NULL; } if (!ret) { + if (!(flags & __GFP_DMA)) { + flags |= __GFP_DMA; + goto again; + } /* * We are either out of memory or the device can't DMA * to GFP_DMA memory; fall back on
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