On Fri, 17 Nov 2017 06:56:12 +0800 <[email protected]> wrote:
> From: Miles Chen <[email protected]>
>
> 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.
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;
_
From 1584306461485814633@xxx Fri Nov 17 09:53:01 +0000 2017
X-GM-THRID: 1584299430012978510
X-Gmail-Labels: Inbox,Category Forums,HistoricalUnread
On Thu, 2017-11-16 at 16:13 -0800, Andrew Morton wrote:
> On Fri, 17 Nov 2017 06:56:12 +0800 <[email protected]> wrote:
>
> > From: Miles Chen <[email protected]>
> >
> > 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;
>
> _
>
>
From 1584299430012978510@xxx Fri Nov 17 08:01:15 +0000 2017
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