| Message ID | 20171116161350.3b8bd1fbcaae8e032441d3e7@linux-foundation.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, 2017-11-16 at 16:13 -0800, Andrew Morton wrote: > On Fri, 17 Nov 2017 06:56:12 +0800 <miles.chen@mediatek.com> wrote: > > > From: Miles Chen <miles.chen@mediatek.com> > > > > dma-debug reports the following warning: > > > > [name:panic&]WARNING: CPU: 3 PID: 298 at kernel-4.4/lib/dma-debug.c:604 > > debug _dma_assert_idle+0x1a8/0x230() > > DMA-API: cpu touching an active dma mapped cacheline [cln=0x00000882300] > > CPU: 3 PID: 298 Comm: vold Tainted: G W O 4.4.22+ #1 > > Hardware name: MT6739 (DT) > > Call trace: > > [<ffffff800808acd0>] dump_backtrace+0x0/0x1d4 > > [<ffffff800808affc>] show_stack+0x14/0x1c > > [<ffffff800838019c>] dump_stack+0xa8/0xe0 > > [<ffffff80080a0594>] warn_slowpath_common+0xf4/0x11c > > [<ffffff80080a061c>] warn_slowpath_fmt+0x60/0x80 > > [<ffffff80083afe24>] debug_dma_assert_idle+0x1a8/0x230 > > [<ffffff80081dca9c>] wp_page_copy.isra.96+0x118/0x520 > > [<ffffff80081de114>] do_wp_page+0x4fc/0x534 > > [<ffffff80081e0a14>] handle_mm_fault+0xd4c/0x1310 > > [<ffffff8008098798>] do_page_fault+0x1c8/0x394 > > [<ffffff800808231c>] do_mem_abort+0x50/0xec > > > > I found that debug_dma_alloc_coherent() and debug_dma_free_coherent() > > assume that dma_alloc_coherent() always returns a linear address. However > > it's possible that dma_alloc_coherent() returns a non-linear address. In > > this case, page_to_pfn(virt_to_page(virt)) will return an incorrect pfn. > > If the pfn is valid and mapped as a COW page, we will hit the warning when > > doing wp_page_copy(). > > > > Fix this by calculating pfn for linear and non-linear addresses. > > > > It's a shame you didn't Cc Christoph, who was the sole reviewer of the > earlier version. > > And it's a shame you didn't capture the result of that review > discussion in the v3 changelog. > > And it's a shame that you didn't describe how this patch differs from > earlier versions. I am truly sorry about this. I was not sure if I can submit a patch based on a linux-next patch, so I submit a new patch based on the latest mainline kernel again. I know how to do this now. I will do it correctly next time. Is there anyway to fix this? (send another patch with v3 discussion and the difference from earlier versions to the commit message). > Oh well, here's the incremental patch: > > --- a/lib/dma-debug.c~dma-debug-fix-incorrect-pfn-calculation-v4 > +++ a/lib/dma-debug.c > @@ -1495,15 +1495,22 @@ void debug_dma_alloc_coherent(struct dev > if (!entry) > return; > > + /* handle vmalloc and linear addresses */ > + if (!is_vmalloc_addr(virt) && !virt_to_page(virt)) > + return; > + > entry->type = dma_debug_coherent; > entry->dev = dev; > - entry->pfn = is_vmalloc_addr(virt) ? vmalloc_to_pfn(virt) : > - page_to_pfn(virt_to_page(virt)); > entry->offset = offset_in_page(virt); > entry->size = size; > entry->dev_addr = dma_addr; > entry->direction = DMA_BIDIRECTIONAL; > > + if (is_vmalloc_addr(virt)) > + entry->pfn = vmalloc_to_pfn(virt); > + else > + entry->pfn = page_to_pfn(virt_to_page(virt)); > + > add_dma_entry(entry); > } > EXPORT_SYMBOL(debug_dma_alloc_coherent); > @@ -1514,14 +1521,21 @@ void debug_dma_free_coherent(struct devi > struct dma_debug_entry ref = { > .type = dma_debug_coherent, > .dev = dev, > - .pfn = is_vmalloc_addr(virt) ? vmalloc_to_pfn(virt) : > - page_to_pfn(virt_to_page(virt)), > .offset = offset_in_page(virt), > .dev_addr = addr, > .size = size, > .direction = DMA_BIDIRECTIONAL, > }; > > + /* handle vmalloc and linear addresses */ > + if (!is_vmalloc_addr(virt) && !virt_to_page(virt)) > + return; > + > + if (is_vmalloc_addr(virt)) > + ref.pfn = vmalloc_to_pfn(virt); > + else > + ref.pfn = page_to_pfn(virt_to_page(virt)); > + > if (unlikely(dma_debug_disabled())) > return; > > _ > >
On Fri, 17 Nov 2017 09:23:18 +0800 Miles Chen <miles.chen@mediatek.com> wrote: > On Thu, 2017-11-16 at 16:13 -0800, Andrew Morton wrote: > > On Fri, 17 Nov 2017 06:56:12 +0800 <miles.chen@mediatek.com> wrote: > > > > > From: Miles Chen <miles.chen@mediatek.com> > > > > > > dma-debug reports the following warning: > > > > > > [name:panic&]WARNING: CPU: 3 PID: 298 at kernel-4.4/lib/dma-debug.c:604 > > > debug _dma_assert_idle+0x1a8/0x230() > > > DMA-API: cpu touching an active dma mapped cacheline [cln=0x00000882300] > > > CPU: 3 PID: 298 Comm: vold Tainted: G W O 4.4.22+ #1 > > > Hardware name: MT6739 (DT) > > > Call trace: > > > [<ffffff800808acd0>] dump_backtrace+0x0/0x1d4 > > > [<ffffff800808affc>] show_stack+0x14/0x1c > > > [<ffffff800838019c>] dump_stack+0xa8/0xe0 > > > [<ffffff80080a0594>] warn_slowpath_common+0xf4/0x11c > > > [<ffffff80080a061c>] warn_slowpath_fmt+0x60/0x80 > > > [<ffffff80083afe24>] debug_dma_assert_idle+0x1a8/0x230 > > > [<ffffff80081dca9c>] wp_page_copy.isra.96+0x118/0x520 > > > [<ffffff80081de114>] do_wp_page+0x4fc/0x534 > > > [<ffffff80081e0a14>] handle_mm_fault+0xd4c/0x1310 > > > [<ffffff8008098798>] do_page_fault+0x1c8/0x394 > > > [<ffffff800808231c>] do_mem_abort+0x50/0xec > > > > > > I found that debug_dma_alloc_coherent() and debug_dma_free_coherent() > > > assume that dma_alloc_coherent() always returns a linear address. However > > > it's possible that dma_alloc_coherent() returns a non-linear address. In > > > this case, page_to_pfn(virt_to_page(virt)) will return an incorrect pfn. > > > If the pfn is valid and mapped as a COW page, we will hit the warning when > > > doing wp_page_copy(). > > > > > > Fix this by calculating pfn for linear and non-linear addresses. > > > > > > > It's a shame you didn't Cc Christoph, who was the sole reviewer of the > > earlier version. > > > > And it's a shame you didn't capture the result of that review > > discussion in the v3 changelog. > > > > And it's a shame that you didn't describe how this patch differs from > > earlier versions. > > > I am truly sorry about this. I was not sure if I can submit a patch > based on a linux-next patch, so I submit a new patch based on the latest > mainline kernel again. > > I know how to do this now. I will do it correctly next time. > > Is there anyway to fix this? (send another patch with v3 discussion and > the difference from earlier versions to the commit message). A complete resend is perfectly OK - I will handle the changelog modifications, etc. My point is that the Cc: line was incomplete and that the changelog is missing information, as described above.
--- a/lib/dma-debug.c~dma-debug-fix-incorrect-pfn-calculation-v4 +++ a/lib/dma-debug.c @@ -1495,15 +1495,22 @@ void debug_dma_alloc_coherent(struct dev if (!entry) return; + /* handle vmalloc and linear addresses */ + if (!is_vmalloc_addr(virt) && !virt_to_page(virt)) + return; + entry->type = dma_debug_coherent; entry->dev = dev; - entry->pfn = is_vmalloc_addr(virt) ? vmalloc_to_pfn(virt) : - page_to_pfn(virt_to_page(virt)); entry->offset = offset_in_page(virt); entry->size = size; entry->dev_addr = dma_addr; entry->direction = DMA_BIDIRECTIONAL; + if (is_vmalloc_addr(virt)) + entry->pfn = vmalloc_to_pfn(virt); + else + entry->pfn = page_to_pfn(virt_to_page(virt)); + add_dma_entry(entry); } EXPORT_SYMBOL(debug_dma_alloc_coherent); @@ -1514,14 +1521,21 @@ void debug_dma_free_coherent(struct devi struct dma_debug_entry ref = { .type = dma_debug_coherent, .dev = dev, - .pfn = is_vmalloc_addr(virt) ? vmalloc_to_pfn(virt) : - page_to_pfn(virt_to_page(virt)), .offset = offset_in_page(virt), .dev_addr = addr, .size = size, .direction = DMA_BIDIRECTIONAL, }; + /* handle vmalloc and linear addresses */ + if (!is_vmalloc_addr(virt) && !virt_to_page(virt)) + return; + + if (is_vmalloc_addr(virt)) + ref.pfn = vmalloc_to_pfn(virt); + else + ref.pfn = page_to_pfn(virt_to_page(virt)); + if (unlikely(dma_debug_disabled())) return;