Currently SEV enabled guests hit might_sleep() warnings when a driver (nvme in this case) allocates through the DMA API in a non-blockable context. Making these unencrypted non-blocking DMA allocations come from the coherent pools prevents this BUG.
BUG: sleeping function called from invalid context at mm/vmalloc.c:1710 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 3383, name: fio 2 locks held by fio/3383: #0: ffff93b6a8568348 (&sb->s_type->i_mutex_key#16){+.+.}, at: ext4_file_write_iter+0xa2/0x5d0 #1: ffffffffa52a61a0 (rcu_read_lock){....}, at: hctx_lock+0x1a/0xe0 CPU: 0 PID: 3383 Comm: fio Tainted: G W 5.5.10 #14 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: dump_stack+0x98/0xd5 ___might_sleep+0x175/0x260 __might_sleep+0x4a/0x80 _vm_unmap_aliases+0x45/0x250 vm_unmap_aliases+0x19/0x20 __set_memory_enc_dec+0xa4/0x130 set_memory_decrypted+0x10/0x20 dma_direct_alloc_pages+0x148/0x150 dma_direct_alloc+0xe/0x10 dma_alloc_attrs+0x86/0xc0 dma_pool_alloc+0x16f/0x2b0 nvme_queue_rq+0x878/0xc30 [nvme] __blk_mq_try_issue_directly+0x135/0x200 blk_mq_request_issue_directly+0x4f/0x80 blk_mq_try_issue_list_directly+0x46/0xb0 blk_mq_sched_insert_requests+0x19b/0x2b0 blk_mq_flush_plug_list+0x22f/0x3b0 blk_flush_plug_list+0xd1/0x100 blk_finish_plug+0x2c/0x40 iomap_dio_rw+0x427/0x490 ext4_file_write_iter+0x181/0x5d0 aio_write+0x109/0x1b0 io_submit_one+0x7d0/0xfa0 __x64_sys_io_submit+0xa2/0x280 do_syscall_64+0x5f/0x250 entry_SYSCALL_64_after_hwframe+0x49/0xbe
Christoph Hellwig (9): dma-direct: remove __dma_direct_free_pages dma-direct: remove the dma_handle argument to __dma_direct_alloc_pages dma-direct: provide mmap and get_sgtable method overrides dma-mapping: merge the generic remapping helpers into dma-direct dma-direct: consolidate the error handling in dma_direct_alloc_pages xtensa: use the generic uncached segment support dma-direct: make uncached_kernel_address more general dma-mapping: DMA_COHERENT_POOL should select GENERIC_ALLOCATOR dma-pool: fix coherent pool allocations for IOMMU mappings
David Rientjes (13): dma-remap: separate DMA atomic pools from direct remap code dma-pool: add additional coherent pools to map to gfp mask dma-pool: dynamically expanding atomic pools dma-direct: atomic allocations must come from atomic coherent pools dma-pool: add pool sizes to debugfs x86/mm: unencrypted non-blocking DMA allocations use coherent pools dma-pool: scale the default DMA coherent pool size with memory capacity dma-pool: decouple DMA_REMAP from DMA_COHERENT_POOL dma-direct: always align allocation size in dma_direct_alloc_pages() dma-direct: re-encrypt memory if dma_direct_alloc_pages() fails dma-direct: check return value when encrypting or decrypting memory dma-direct: add missing set_memory_decrypted() for coherent mapping dma-mapping: warn when coherent pool is depleted
Geert Uytterhoeven (1): dma-pool: fix too large DMA pools on medium memory size systems
Huang Shijie (1): lib/genalloc.c: rename addr_in_gen_pool to gen_pool_has_addr
Nicolas Saenz Julienne (6): dma-direct: provide function to check physical memory area validity dma-pool: get rid of dma_in_atomic_pool() dma-pool: introduce dma_guess_pool() dma-pool: make sure atomic pool suits device dma-pool: do not allocate pool memory from CMA dma/direct: turn ARCH_ZONE_DMA_BITS into a variable
Documentation/core-api/genalloc.rst | 2 +- arch/Kconfig | 8 +- arch/arc/Kconfig | 1 - arch/arm/Kconfig | 1 - arch/arm/mm/dma-mapping.c | 8 +- arch/arm64/Kconfig | 1 - arch/arm64/mm/init.c | 9 +- arch/ia64/Kconfig | 2 +- arch/ia64/kernel/dma-mapping.c | 6 - arch/microblaze/Kconfig | 3 +- arch/microblaze/mm/consistent.c | 2 +- arch/mips/Kconfig | 7 +- arch/mips/mm/dma-noncoherent.c | 8 +- arch/nios2/Kconfig | 3 +- arch/nios2/mm/dma-mapping.c | 2 +- arch/powerpc/include/asm/page.h | 9 - arch/powerpc/mm/mem.c | 20 +- arch/powerpc/platforms/Kconfig.cputype | 1 - arch/s390/include/asm/page.h | 2 - arch/s390/mm/init.c | 1 + arch/x86/Kconfig | 1 + arch/xtensa/Kconfig | 6 +- arch/xtensa/include/asm/platform.h | 27 --- arch/xtensa/kernel/Makefile | 3 +- arch/xtensa/kernel/pci-dma.c | 121 ++--------- drivers/iommu/dma-iommu.c | 5 +- drivers/misc/sram-exec.c | 2 +- include/linux/dma-direct.h | 12 +- include/linux/dma-mapping.h | 7 +- include/linux/dma-noncoherent.h | 4 +- include/linux/genalloc.h | 2 +- kernel/dma/Kconfig | 20 +- kernel/dma/Makefile | 1 + kernel/dma/direct.c | 224 ++++++++++++++++---- kernel/dma/mapping.c | 45 +---- kernel/dma/pool.c | 270 +++++++++++++++++++++++++ kernel/dma/remap.c | 176 +--------------- lib/genalloc.c | 5 +- 38 files changed, 564 insertions(+), 463 deletions(-) create mode 100644 kernel/dma/pool.c