c37c792dec
We allocate only the first level of multilevel TCE tables for KVM already (alloc_userspace_copy==true), and the rest is allocated on demand. This is not enabled though for bare metal. This removes the KVM limitation (implicit, via the alloc_userspace_copy parameter) and always allocates just the first level. The on-demand allocation of missing levels is already implemented. As from now on DMA map might happen with disabled interrupts, this allocates TCEs with GFP_ATOMIC; otherwise lockdep reports errors 1]. In practice just a single page is allocated there so chances for failure are quite low. To save time when creating a new clean table, this skips non-allocated indirect TCE entries in pnv_tce_free just like we already do in the VFIO IOMMU TCE driver. This changes the default level number from 1 to 2 to reduce the amount of memory required for the default 32bit DMA window at the boot time. The default window size is up to 2GB which requires 4MB of TCEs which is unlikely to be used entirely or at all as most devices these days are 64bit capable so by switching to 2 levels by default we save 4032KB of RAM per a device. While at this, add __GFP_NOWARN to alloc_pages_node() as the userspace can trigger this path via VFIO, see the failure and try creating a table again with different parameters which might succeed. [1]: === BUG: sleeping function called from invalid context at mm/page_alloc.c:4596 in_atomic(): 1, irqs_disabled(): 1, pid: 1038, name: scsi_eh_1 2 locks held by scsi_eh_1/1038: #0: 000000005efd659a (&host->eh_mutex){+.+.}, at: ata_eh_acquire+0x34/0x80 #1: 0000000006cf56a6 (&(&host->lock)->rlock){....}, at: ata_exec_internal_sg+0xb0/0x5c0 irq event stamp: 500 hardirqs last enabled at (499): [<c000000000cb8a74>] _raw_spin_unlock_irqrestore+0x94/0xd0 hardirqs last disabled at (500): [<c000000000cb85c4>] _raw_spin_lock_irqsave+0x44/0x120 softirqs last enabled at (0): [<c000000000101120>] copy_process.isra.4.part.5+0x640/0x1a80 softirqs last disabled at (0): [<0000000000000000>] 0x0 CPU: 73 PID: 1038 Comm: scsi_eh_1 Not tainted 5.2.0-rc6-le_nv2_aikATfstn1-p1 #634 Call Trace: [c000003d064cef50] [c000000000c8e6c4] dump_stack+0xe8/0x164 (unreliable) [c000003d064cefa0] [c00000000014ed78] ___might_sleep+0x2f8/0x310 [c000003d064cf020] [c0000000003ca084] __alloc_pages_nodemask+0x2a4/0x1560 [c000003d064cf220] [c0000000000c2530] pnv_alloc_tce_level.isra.0+0x90/0x130 [c000003d064cf290] [c0000000000c2888] pnv_tce+0x128/0x3b0 [c000003d064cf360] [c0000000000c2c00] pnv_tce_build+0xb0/0xf0 [c000003d064cf3c0] [c0000000000bbd9c] pnv_ioda2_tce_build+0x3c/0xb0 [c000003d064cf400] [c00000000004cfe0] ppc_iommu_map_sg+0x210/0x550 [c000003d064cf510] [c00000000004b7a4] dma_iommu_map_sg+0x74/0xb0 [c000003d064cf530] [c000000000863944] ata_qc_issue+0x134/0x470 [c000003d064cf5b0] [c000000000863ec4] ata_exec_internal_sg+0x244/0x5c0 [c000003d064cf700] [c0000000008642d0] ata_exec_internal+0x90/0xe0 [c000003d064cf780] [c0000000008650ac] ata_dev_read_id+0x2ec/0x640 [c000003d064cf8d0] [c000000000878e28] ata_eh_recover+0x948/0x16d0 [c000003d064cfa10] [c00000000087d760] sata_pmp_error_handler+0x480/0xbf0 [c000003d064cfbc0] [c000000000884624] ahci_error_handler+0x74/0xe0 [c000003d064cfbf0] [c000000000879fa8] ata_scsi_port_error_handler+0x2d8/0x7c0 [c000003d064cfca0] [c00000000087a544] ata_scsi_error+0xb4/0x100 [c000003d064cfd00] [c000000000802450] scsi_error_handler+0x120/0x510 [c000003d064cfdb0] [c000000000140c48] kthread+0x1b8/0x1c0 [c000003d064cfe20] [c00000000000bd8c] ret_from_kernel_thread+0x5c/0x70 ata1: SATA link up 6.0 Gbps (SStatus 133 SControl 300) irq event stamp: 2305 ======================================================== hardirqs last enabled at (2305): [<c00000000000e4c8>] fast_exc_return_irq+0x28/0x34 hardirqs last disabled at (2303): [<c000000000cb9fd0>] __do_softirq+0x4a0/0x654 WARNING: possible irq lock inversion dependency detected 5.2.0-rc6-le_nv2_aikATfstn1-p1 #634 Tainted: G W softirqs last enabled at (2304): [<c000000000cba054>] __do_softirq+0x524/0x654 softirqs last disabled at (2297): [<c00000000010f278>] irq_exit+0x128/0x180 -------------------------------------------------------- swapper/0/0 just changed the state of lock: 0000000006cf56a6 (&(&host->lock)->rlock){-...}, at: ahci_single_level_irq_intr+0xac/0x120 but this lock took another, HARDIRQ-unsafe lock in the past: (fs_reclaim){+.+.} and interrupts could create inverse lock ordering between them. other info that might help us debug this: Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); local_irq_disable(); lock(&(&host->lock)->rlock); lock(fs_reclaim); <Interrupt> lock(&(&host->lock)->rlock); *** DEADLOCK *** no locks held by swapper/0/0. the shortest dependencies between 2nd lock and 1st lock: -> (fs_reclaim){+.+.} ops: 167579 { HARDIRQ-ON-W at: lock_acquire+0xf8/0x2a0 fs_reclaim_acquire.part.23+0x44/0x60 kmem_cache_alloc_node_trace+0x80/0x590 alloc_desc+0x64/0x270 __irq_alloc_descs+0x2e4/0x3a0 irq_domain_alloc_descs+0xb0/0x150 irq_create_mapping+0x168/0x2c0 xics_smp_probe+0x2c/0x98 pnv_smp_probe+0x40/0x9c smp_prepare_cpus+0x524/0x6c4 kernel_init_freeable+0x1b4/0x650 kernel_init+0x2c/0x148 ret_from_kernel_thread+0x5c/0x70 SOFTIRQ-ON-W at: lock_acquire+0xf8/0x2a0 fs_reclaim_acquire.part.23+0x44/0x60 kmem_cache_alloc_node_trace+0x80/0x590 alloc_desc+0x64/0x270 __irq_alloc_descs+0x2e4/0x3a0 irq_domain_alloc_descs+0xb0/0x150 irq_create_mapping+0x168/0x2c0 xics_smp_probe+0x2c/0x98 pnv_smp_probe+0x40/0x9c smp_prepare_cpus+0x524/0x6c4 kernel_init_freeable+0x1b4/0x650 kernel_init+0x2c/0x148 ret_from_kernel_thread+0x5c/0x70 INITIAL USE at: lock_acquire+0xf8/0x2a0 fs_reclaim_acquire.part.23+0x44/0x60 kmem_cache_alloc_node_trace+0x80/0x590 alloc_desc+0x64/0x270 __irq_alloc_descs+0x2e4/0x3a0 irq_domain_alloc_descs+0xb0/0x150 irq_create_mapping+0x168/0x2c0 xics_smp_probe+0x2c/0x98 pnv_smp_probe+0x40/0x9c smp_prepare_cpus+0x524/0x6c4 kernel_init_freeable+0x1b4/0x650 kernel_init+0x2c/0x148 ret_from_kernel_thread+0x5c/0x70 } === Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Reviewed-by: Alistair Popple <alistair@popple.id.au> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20190718051139.74787-4-aik@ozlabs.ru |
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README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.