Messages in this thread | | | Date | Wed, 9 Jan 2013 11:13:26 -0800 | Subject | Re: [PATCH v7u1 26/31] x86: Don't enable swiotlb if there is not enough ram for it | From | Yinghai Lu <> |
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On Wed, Jan 9, 2013 at 10:01 AM, Shuah Khan <shuahkhan@gmail.com> wrote: > After several revisions, I am loosing track. Could you please write a > change log and explain the change to the existing behavior. If you > could addresses the following areas, it will be easier figure if we > are missing something (if any): > > 1. What happens when switolb is forced with iommu=soft on a system > with and without not enough low mem?
panic later when device try to map_single with it. instead of panic early during swiotlb allocation.
> 2. What happens when swiotlb is not forced, but iommu driver sets > swiotlb=1 after it gets done with its iommu initialization on a system > with and without enough low mem.
panic later when device try to map_single with it. instead of panic early during swiotlb allocation.
> 3. What happens when nopanic is used and when will the system fail? > Will it fail when driver runs into errors. I am hoping this won't be a > silent failure. Please see more on this below:
according to eric/konrad, I make all use nopanic path, and only mips, and x86-xen still panic early when swiotlb_init_with_tab is called directly.
hope mips, and x86-xen guys could convert to calling swiotlb_init instead.
> > I did dma mapping error analysis a few months ago and found several > drivers that don't check dma mapping errors, don't unmap dma buffers > etc. Returning mapping error from switolb could cause problems when we > have drivers that don't check mapping errors. These drivers might not > fail cleanly either and could cause data corruption.
Now, we are using panic with them, later after those drivers get fixed, we can change to returning MAP_ERROR instead.
> > Here is a link to the dma mapping error analysis I did: > > http://linuxdriverproject.org/mediawiki/index.php/DMA_Mapping_Error_Analysis
good, looks like need one generic way to fix the problem, like another wrapper?
Thanks
Yinghai
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