| Message ID | 1506432287-7214-1-git-send-email-miles.chen@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 26/09/17 14:24, miles.chen@mediatek.com wrote: > From: Miles Chen <miles.chen@mediatek.com> > > dma-debug report 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() > always use type "dma_debug_coherent" and assume that dma_alloc_coherent() > always returns a linear address. > > However if a device returns false on is_device_dma_coherent(), > dma_alloc_coherent() will create another non-cacheable mapping > (also non linear). 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 correct pfn if is_device_dma_coherent() > returns false. As the inevitable storm of kbuild robot reports will tell you soon, you can't do that: is_device_dma_coherent() is a private helper between arm{,64} arch code and xen, and should not be used anywhere else. > Signed-off-by: Miles Chen <miles.chen@mediatek.com> > --- > lib/dma-debug.c | 20 ++++++++++++++------ > 1 file changed, 14 insertions(+), 6 deletions(-) > > diff --git a/lib/dma-debug.c b/lib/dma-debug.c > index ea4cc3d..b17e56e 100644 > --- a/lib/dma-debug.c > +++ b/lib/dma-debug.c > @@ -47,6 +47,8 @@ enum { > dma_debug_sg, > dma_debug_coherent, > dma_debug_resource, > + dma_debug_noncoherent, > + nr_dma_debug_types, > }; > > enum map_err_types { > @@ -154,9 +156,9 @@ static inline bool dma_debug_disabled(void) > [MAP_ERR_CHECKED] = "dma map error checked", > }; > > -static const char *type2name[5] = { "single", "page", > +static const char *type2name[nr_dma_debug_types] = { "single", "page", > "scather-gather", "coherent", > - "resource" }; > + "resource", "noncoherent" }; > > static const char *dir2name[4] = { "DMA_BIDIRECTIONAL", "DMA_TO_DEVICE", > "DMA_FROM_DEVICE", "DMA_NONE" }; > @@ -1484,6 +1486,7 @@ void debug_dma_alloc_coherent(struct device *dev, size_t size, > dma_addr_t dma_addr, void *virt) > { > struct dma_debug_entry *entry; > + bool coherent = is_device_dma_coherent(dev); > > if (unlikely(dma_debug_disabled())) > return; > @@ -1495,9 +1498,11 @@ void debug_dma_alloc_coherent(struct device *dev, size_t size, > if (!entry) > return; > > - entry->type = dma_debug_coherent; > + entry->type = coherent ? dma_debug_coherent : > + dma_debug_noncoherent; > entry->dev = dev; > - entry->pfn = page_to_pfn(virt_to_page(virt)); There are more architectures where the virtual address returned by dma_alloc_coherent is not a linear map address - some just have a static offset between cacheable and non-cacheable aliases - so there may be other cases where this is the wrong calculation, but at least those probably don't trigger the problematic false-positive. That said, the cases where coherent allocations *are* dynamically remapped should be easy enough to handle properly without having to resort to dodgy hacks: if (is_vmalloc_addr(virt)) pfn = vmalloc_to_pfn(virt); else pfn = page_to_pfn(virt_to_page(virt)); Simple. > + entry->pfn = coherent ? page_to_pfn(virt_to_page(virt)) : > + dma_addr >> PAGE_SHIFT; And in particular, this is just as likely to just give *different* false positives, since there's no guarantee whatsoever that dma_addr has any relationship to the appropriate pfn. Robin. > entry->offset = offset_in_page(virt); > entry->size = size; > entry->dev_addr = dma_addr; > @@ -1510,10 +1515,13 @@ void debug_dma_alloc_coherent(struct device *dev, size_t size, > void debug_dma_free_coherent(struct device *dev, size_t size, > void *virt, dma_addr_t addr) > { > + bool coherent = is_device_dma_coherent(dev); > struct dma_debug_entry ref = { > - .type = dma_debug_coherent, > + .type = coherent ? dma_debug_coherent : > + dma_debug_noncoherent, > .dev = dev, > - .pfn = page_to_pfn(virt_to_page(virt)), > + .pfn = coherent ? page_to_pfn(virt_to_page(virt)) : > + addr >> PAGE_SHIFT, > .offset = offset_in_page(virt), > .dev_addr = addr, > .size = size, >
On Tue, 2017-09-26 at 15:53 +0100, Robin Murphy wrote: > On 26/09/17 14:24, miles.chen@mediatek.com wrote: > > From: Miles Chen <miles.chen@mediatek.com> > > > > dma-debug report 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() > > always use type "dma_debug_coherent" and assume that dma_alloc_coherent() > > always returns a linear address. > > > > However if a device returns false on is_device_dma_coherent(), > > dma_alloc_coherent() will create another non-cacheable mapping > > (also non linear). 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 correct pfn if is_device_dma_coherent() > > returns false. > > As the inevitable storm of kbuild robot reports will tell you soon, you > can't do that: is_device_dma_coherent() is a private helper between > arm{,64} arch code and xen, and should not be used anywhere else. thanks for that. I should not use the private helper function here. > > Signed-off-by: Miles Chen <miles.chen@mediatek.com> > > --- > > lib/dma-debug.c | 20 ++++++++++++++------ > > 1 file changed, 14 insertions(+), 6 deletions(-) > > > > diff --git a/lib/dma-debug.c b/lib/dma-debug.c > > index ea4cc3d..b17e56e 100644 > > --- a/lib/dma-debug.c > > +++ b/lib/dma-debug.c > > @@ -47,6 +47,8 @@ enum { > > dma_debug_sg, > > dma_debug_coherent, > > dma_debug_resource, > > + dma_debug_noncoherent, > > + nr_dma_debug_types, > > }; > > > > enum map_err_types { > > @@ -154,9 +156,9 @@ static inline bool dma_debug_disabled(void) > > [MAP_ERR_CHECKED] = "dma map error checked", > > }; > > > > -static const char *type2name[5] = { "single", "page", > > +static const char *type2name[nr_dma_debug_types] = { "single", "page", > > "scather-gather", "coherent", > > - "resource" }; > > + "resource", "noncoherent" }; > > > > static const char *dir2name[4] = { "DMA_BIDIRECTIONAL", "DMA_TO_DEVICE", > > "DMA_FROM_DEVICE", "DMA_NONE" }; > > @@ -1484,6 +1486,7 @@ void debug_dma_alloc_coherent(struct device *dev, size_t size, > > dma_addr_t dma_addr, void *virt) > > { > > struct dma_debug_entry *entry; > > + bool coherent = is_device_dma_coherent(dev); > > > > if (unlikely(dma_debug_disabled())) > > return; > > @@ -1495,9 +1498,11 @@ void debug_dma_alloc_coherent(struct device *dev, size_t size, > > if (!entry) > > return; > > > > - entry->type = dma_debug_coherent; > > + entry->type = coherent ? dma_debug_coherent : > > + dma_debug_noncoherent; > > entry->dev = dev; > > - entry->pfn = page_to_pfn(virt_to_page(virt)); > > There are more architectures where the virtual address returned by > dma_alloc_coherent is not a linear map address - some just have a static > offset between cacheable and non-cacheable aliases - so there may be > other cases where this is the wrong calculation, but at least those > probably don't trigger the problematic false-positive. > > That said, the cases where coherent allocations *are* dynamically > remapped should be easy enough to handle properly without having to > resort to dodgy hacks: > > if (is_vmalloc_addr(virt)) > pfn = vmalloc_to_pfn(virt); > else > pfn = page_to_pfn(virt_to_page(virt)); > > Simple. Thanks for your advice. I'll try this approach. Miles > > > + entry->pfn = coherent ? page_to_pfn(virt_to_page(virt)) : > > + dma_addr >> PAGE_SHIFT; > > And in particular, this is just as likely to just give *different* false > positives, since there's no guarantee whatsoever that dma_addr has any > relationship to the appropriate pfn. > > Robin. > > > entry->offset = offset_in_page(virt); > > entry->size = size; > > entry->dev_addr = dma_addr; > > @@ -1510,10 +1515,13 @@ void debug_dma_alloc_coherent(struct device *dev, size_t size, > > void debug_dma_free_coherent(struct device *dev, size_t size, > > void *virt, dma_addr_t addr) > > { > > + bool coherent = is_device_dma_coherent(dev); > > struct dma_debug_entry ref = { > > - .type = dma_debug_coherent, > > + .type = coherent ? dma_debug_coherent : > > + dma_debug_noncoherent, > > .dev = dev, > > - .pfn = page_to_pfn(virt_to_page(virt)), > > + .pfn = coherent ? page_to_pfn(virt_to_page(virt)) : > > + addr >> PAGE_SHIFT, > > .offset = offset_in_page(virt), > > .dev_addr = addr, > > .size = size, > > >
diff --git a/lib/dma-debug.c b/lib/dma-debug.c index ea4cc3d..b17e56e 100644 --- a/lib/dma-debug.c +++ b/lib/dma-debug.c @@ -47,6 +47,8 @@ enum { dma_debug_sg, dma_debug_coherent, dma_debug_resource, + dma_debug_noncoherent, + nr_dma_debug_types, }; enum map_err_types { @@ -154,9 +156,9 @@ static inline bool dma_debug_disabled(void) [MAP_ERR_CHECKED] = "dma map error checked", }; -static const char *type2name[5] = { "single", "page", +static const char *type2name[nr_dma_debug_types] = { "single", "page", "scather-gather", "coherent", - "resource" }; + "resource", "noncoherent" }; static const char *dir2name[4] = { "DMA_BIDIRECTIONAL", "DMA_TO_DEVICE", "DMA_FROM_DEVICE", "DMA_NONE" }; @@ -1484,6 +1486,7 @@ void debug_dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t dma_addr, void *virt) { struct dma_debug_entry *entry; + bool coherent = is_device_dma_coherent(dev); if (unlikely(dma_debug_disabled())) return; @@ -1495,9 +1498,11 @@ void debug_dma_alloc_coherent(struct device *dev, size_t size, if (!entry) return; - entry->type = dma_debug_coherent; + entry->type = coherent ? dma_debug_coherent : + dma_debug_noncoherent; entry->dev = dev; - entry->pfn = page_to_pfn(virt_to_page(virt)); + entry->pfn = coherent ? page_to_pfn(virt_to_page(virt)) : + dma_addr >> PAGE_SHIFT; entry->offset = offset_in_page(virt); entry->size = size; entry->dev_addr = dma_addr; @@ -1510,10 +1515,13 @@ void debug_dma_alloc_coherent(struct device *dev, size_t size, void debug_dma_free_coherent(struct device *dev, size_t size, void *virt, dma_addr_t addr) { + bool coherent = is_device_dma_coherent(dev); struct dma_debug_entry ref = { - .type = dma_debug_coherent, + .type = coherent ? dma_debug_coherent : + dma_debug_noncoherent, .dev = dev, - .pfn = page_to_pfn(virt_to_page(virt)), + .pfn = coherent ? page_to_pfn(virt_to_page(virt)) : + addr >> PAGE_SHIFT, .offset = offset_in_page(virt), .dev_addr = addr, .size = size,