Re: [PATCH] powerpc: convert 'iommu_alloc failed' messages to dynamic debug
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: 2016-06-11 23:02:36
On Fri, 2016-06-10 at 10:03 -0300, Mauricio Faria de Oliveira wrote:
This prevents flooding the logs with 'iommu_alloc failed' messages while I/O is performed (normally) to very fast devices (e.g. NVMe). That error is not necessarily a problem; device drivers can retry later / reschedule the requests for which the allocation failed, and handle things gracefully for the caller stack on top of them. This helps at least with NVMe devices without "64-bit"/direct DMA window scenarios (e.g., systems with more than a few terabytes of memory, on which DDW cannot be enabled, currently), where just an 'dd' command can trigger errors.
I'm not fan of this. This is a very useful message to diagnose why, for example, your network adapter is not working properly. A lot of drivers don't deal well with IOMMU errors. The fact that NVME trigger these is a problem that needs to be solved differently. Cheers, Ben.
quoted hunk ↗ jump to hunk
# dd if=/dev/zero of=/dev/nvme0n1p1 bs=64k count=512k <...> # echo $? 0 # dmesg nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c000000151c90000 npages 16 nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c000000151c90000 npages 16 nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c000000151c90000 npages 16 <...> ppc_iommu_map_sg: 8186 callbacks suppressed nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c0000000fa5c0000 npages 16 nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c000000100440000 npages 16 nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c000000100440000 npages 16 <...> ppc_iommu_map_sg: 5707 callbacks suppressed nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c0000000b5f50000 npages 16 nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c0000000b5c60000 npages 16 nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c0000000b4b30000 npages 16 <...> Tested on next-20160609. Signed-off-by: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.co m> --- arch/powerpc/kernel/iommu.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-)diff --git a/arch/powerpc/kernel/iommu.cb/arch/powerpc/kernel/iommu.c index a8e3490..b585bdc 100644--- a/arch/powerpc/kernel/iommu.c +++ b/arch/powerpc/kernel/iommu.c@@ -479,10 +479,9 @@ int ppc_iommu_map_sg(struct device *dev, structiommu_table *tbl, /* Handle failure */ if (unlikely(entry == DMA_ERROR_CODE)) { - if (printk_ratelimit()) - dev_info(dev, "iommu_alloc failed, tbl %p " - "vaddr %lx npages %lu\n", tbl, vaddr, - npages); + dev_dbg_ratelimited(dev, "iommu_alloc failed, tbl %p " + "vaddr %lx npages %lu\n", tbl, vaddr, + npages); goto failure; }@@ -776,11 +775,9 @@ dma_addr_t iommu_map_page(struct device *dev,struct iommu_table *tbl, mask >> tbl->it_page_shift, align, attrs); if (dma_handle == DMA_ERROR_CODE) { - if (printk_ratelimit()) { - dev_info(dev, "iommu_alloc failed, tbl %p " - "vaddr %p npages %d\n", tbl, vaddr, - npages); - } + dev_dbg_ratelimited(dev, "iommu_alloc failed, tbl %p " + "vaddr %p npages %d\n", tbl, vaddr, + npages); } else dma_handle |= (uaddr & ~IOMMU_PAGE_MASK(tbl)); }