Hello Randy,
Thanks for your quick review. Randy Dunlap <rdun...@infradead.org> writes: > On 08/24/2018 09:25 AM, Thiago Jung Bauermann wrote: >> From: Anshuman Khandual <khand...@linux.vnet.ibm.com> >> >> SWIOTLB buffer default size (64MB) is not enough for large sequential write >> operations which eventually leads to kernel crash like here. >> >> virtio-pci 0000:00:05.0: swiotlb buffer is full (sz: 327680 bytes) >> virtio-pci 0000:00:05.0: DMA: Out of SW-IOMMU space for 327680 bytes >> Kernel panic - not syncing: DMA: Random memory could be DMA read >> CPU: 12 PID: 3985 Comm: mkfs.ext4 Not tainted 4.18.0-rc4+ #285 >> Call Trace: >> [c0000007d2a27020] [c000000000cfdffc] dump_stack+0xb0/0xf4 (unreliable) >> [c0000007d2a27060] [c000000000112a98] panic+0x140/0x328 >> [c0000007d2a270f0] [c0000000001b4f88] swiotlb_full+0x108/0x130 >> [c0000007d2a27180] [c0000000001b5f6c] swiotlb_map_page+0x25c/0x2c0 >> [c0000007d2a271e0] [c0000000007bfaf8] vring_map_one_sg.isra.0+0x58/0x70 >> [c0000007d2a27200] [c0000000007c08dc] virtqueue_add_sgs+0x1bc/0x690 >> [c0000007d2a272f0] [d0000000042a1280] virtio_queue_rq+0x358/0x4a0 >> [virtio_blk] >> [c0000007d2a273d0] [c0000000006b5d68] blk_mq_dispatch_rq_list+0x1f8/0x6d0 >> .................. >> >> Increase the SWIOTLB size to 1GB on Ultravisor based secure guests. >> >> Signed-off-by: Anshuman Khandual <khand...@linux.vnet.ibm.com> >> Signed-off-by: Thiago Jung Bauermann <bauer...@linux.ibm.com> >> --- >> arch/powerpc/Kconfig | 5 +++++ >> kernel/dma/swiotlb.c | 5 +++++ >> 2 files changed, 10 insertions(+) >> >> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig >> index 1466d1234723..fee7194ce9e4 100644 >> --- a/arch/powerpc/Kconfig >> +++ b/arch/powerpc/Kconfig >> @@ -457,6 +457,11 @@ config PPC_SVM >> >> If unsure, say "N". >> >> +config SWIOTLB_DEFAULT_SIZE >> + int "Size of Software I/O TLB buffer (in MiB)" >> + default "1024" > > I would add a "range" to limit (restrict) how small or large that can be. > E.g.: > > range 16 102400 > > or even smaller for the maximum value... That's an interesting idea. Since this config option is restricted to PPC_SVM it may be possible to find out what reasonable limits would be. I'll have to experiment a bit to find out. Though I can say that 16 MB is too small since even with 64 MB the kernel panics with the simple task of formatting a filesystem... -- Thiago Jung Bauermann IBM Linux Technology Center
