On Thu, Jul 30 2015, Feng Tang wrote: > When system(one x86 soc) boot, we saw many normal dma allocation requests > goes to cma area. The call chain is > dma_generic_alloc_coherent > dma_alloc_from_contiguous -- arch/x86/kernel/pci-dma.c > cma_alloc(dev_get_cma_area(dev), count, align) > > Current dev_get_cma_area() will return a valid "cma" anyway. Then all > these requests will be taken as valid cma request, and get pages from > cma area, which has 2 problems: > 1. make the cma area fragmented > 2. confuse the cma reservation, usually cma memory size is set according > to the expectation of system scenario, these unexpected requests > will affect the designed cma usage. > > So this patch will enforce the judgement, and only return valid "cma" > for real cma user, thus make normal user like IO device driver not > abuse cma reserved region.
Just don’t set dma_contiguous_default_area. This patch defeats the purpose of a *default* area. > Signed-off-by: Feng Tang <[email protected]> > --- > include/linux/dma-contiguous.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/include/linux/dma-contiguous.h b/include/linux/dma-contiguous.h > index 569bbd0..d6ccc19 100644 > --- a/include/linux/dma-contiguous.h > +++ b/include/linux/dma-contiguous.h > @@ -66,7 +66,8 @@ static inline struct cma *dev_get_cma_area(struct device > *dev) > { > if (dev && dev->cma_area) > return dev->cma_area; > - return dma_contiguous_default_area; > + else > + return NULL; > } > > static inline void dev_set_cma_area(struct device *dev, struct cma *cma) > -- > 1.7.9.5 > -- Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o ..o | Computer Science, Michał “mina86” Nazarewicz (o o) ooo +--<[email protected]>--<xmpp:[email protected]>--ooO--(_)--Ooo-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
