Hello! > > Probably you might have to set "coherent_pool" size in bootargs to a > > higher value. > > Can you please check. > > I have tried to do this. I was able to enlarge the pool up to 4MB, and still > got allocation > failures. At 8MB pool preallocation stops working: > --- cut --- > Call trace: > [<ffffffc00012ddb8>] __alloc_pages_nodemask+0x4f4/0x7d4 > [<ffffffc0007be370>] atomic_pool_init+0x60/0x1a4 > [<ffffffc0007be4d4>] arm64_dma_init+0x20/0x28 > [<ffffffc000082848>] do_one_initcall+0x8c/0x1a4 > [<ffffffc0007baac0>] kernel_init_freeable+0x154/0x1f4 > [<ffffffc0005c2b14>] kernel_init+0x10/0xd8 > DMA: failed to allocate 8192 KiB pool for atomic coherent allocation > --- cut --- > and i get even worse faults in the driver. > > I know that it is possible to allocate larger pools by setting > CONFIG_FORCE_MAX_ZONEORDER, > but: > a) This is done on per-platform basis. For ThunderX we used to have a patch > (http://www.spinics.net/lists/arm-kernel/msg415457.html), which never made it > upstream, > because vGIC fixes stopped requiring it at some point. And also we may want > to use the nicvf > driver not only on actual hardware, but also inside virtual machine in KVM. > So do we need to > set CONFIG_FORCE_MAX_ZONEORDER for virt too? And what if at some point qemu > emulates not only > "virt", but some other machine (let's say AMD X-Gene), and we run it on > ThunderX and want to > use nicvf with this model? > b) IMHO it's not good to have a driver which simply does not work without > some obscure option > in boot arguments. > > So, i see several possible ways to solve this: > > 1. Introduce some mechanism which would allow the driver to tell the kernel > that it needs > coherent pool of large size. Can be problematic because the driver can be a > module, and pool > allocation happens early. > 2. Can we use some other method for allocating queues, which would not > require such a huge > coherent pool? > 3. The driver could check value of atomic_pool_size and adjust own memory > requirements > accordingly. This indeed looks like a quick hack, but would at least make > things running > quickly.
I have also noticed that CONFIG_DMA_CMA is turned off in my kernel. I guess it was a leftover from old defconfig, because i carry over my .config from version to version. I enabled it and rebuilt the kernel, but in order to get the driver working with this patch i had to also add cma=32M option to kernel arguments. With default of 16M the allocation still fails. Should we add Kconfig dependencies? Kind regards, Pavel Fedin Expert Engineer Samsung Electronics Research center Russia -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
