Support arm (i.e. 32-bit) #79
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ojeda
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Sep 12, 2023
We try to build affinity mask via create_affinity_masks() unconditionally which may lead several issues: - the affinity mask is not used for parent without affinity support (only VDUSE support the affinity now) - the logic of create_affinity_masks() might not work for devices other than block. For example it's not rare in the networking device where the number of queues could exceed the number of CPUs. Such case breaks the current affinity logic which is based on group_cpus_evenly() who assumes the number of CPUs are not less than the number of groups. This can trigger a warning[1]: if (ret >= 0) WARN_ON(nr_present + nr_others < numgrps); Fixing this by only build the affinity masks only when - Driver passes affinity descriptor, driver like virtio-blk can make sure to limit the number of queues when it exceeds the number of CPUs - Parent support affinity setting config ops This help to avoid the warning. More optimizations could be done on top. [1] [ 682.146655] WARNING: CPU: 6 PID: 1550 at lib/group_cpus.c:400 group_cpus_evenly+0x1aa/0x1c0 [ 682.146668] CPU: 6 PID: 1550 Comm: vdpa Not tainted 6.5.0-rc5jason+ #79 [ 682.146671] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014 [ 682.146673] RIP: 0010:group_cpus_evenly+0x1aa/0x1c0 [ 682.146676] Code: 4c 89 e0 5b 5d 41 5c 41 5d 41 5e c3 cc cc cc cc e8 1b c4 74 ff 48 89 ef e8 13 ac 98 ff 4c 89 e7 45 31 e4 e8 08 ac 98 ff eb c2 <0f> 0b eb b6 e8 fd 05 c3 00 45 31 e4 eb e5 cc cc cc cc cc cc cc cc [ 682.146679] RSP: 0018:ffffc9000215f498 EFLAGS: 00010293 [ 682.146682] RAX: 000000000001f1e0 RBX: 0000000000000041 RCX: 0000000000000000 [ 682.146684] RDX: ffff888109922058 RSI: 0000000000000041 RDI: 0000000000000030 [ 682.146686] RBP: ffff888109922058 R08: ffffc9000215f498 R09: ffffc9000215f4a0 [ 682.146687] R10: 00000000000198d0 R11: 0000000000000030 R12: ffff888107e02800 [ 682.146689] R13: 0000000000000030 R14: 0000000000000030 R15: 0000000000000041 [ 682.146692] FS: 00007fef52315740(0000) GS:ffff888237380000(0000) knlGS:0000000000000000 [ 682.146695] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 682.146696] CR2: 00007fef52509000 CR3: 0000000110dbc004 CR4: 0000000000370ee0 [ 682.146698] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 682.146700] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 682.146701] Call Trace: [ 682.146703] <TASK> [ 682.146705] ? __warn+0x7b/0x130 [ 682.146709] ? group_cpus_evenly+0x1aa/0x1c0 [ 682.146712] ? report_bug+0x1c8/0x1e0 [ 682.146717] ? handle_bug+0x3c/0x70 [ 682.146721] ? exc_invalid_op+0x14/0x70 [ 682.146723] ? asm_exc_invalid_op+0x16/0x20 [ 682.146727] ? group_cpus_evenly+0x1aa/0x1c0 [ 682.146729] ? group_cpus_evenly+0x15c/0x1c0 [ 682.146731] create_affinity_masks+0xaf/0x1a0 [ 682.146735] virtio_vdpa_find_vqs+0x83/0x1d0 [ 682.146738] ? __pfx_default_calc_sets+0x10/0x10 [ 682.146742] virtnet_find_vqs+0x1f0/0x370 [ 682.146747] virtnet_probe+0x501/0xcd0 [ 682.146749] ? vp_modern_get_status+0x12/0x20 [ 682.146751] ? get_cap_addr.isra.0+0x10/0xc0 [ 682.146754] virtio_dev_probe+0x1af/0x260 [ 682.146759] really_probe+0x1a5/0x410 Fixes: 3dad568 ("virtio-vdpa: Support interrupt affinity spreading mechanism") Signed-off-by: Jason Wang <[email protected]> Message-Id: <[email protected]> Signed-off-by: Michael S. Tsirkin <[email protected]>
ojeda
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Jul 29, 2024
When tries to demote 1G hugetlb folios, a lockdep warning is observed: ============================================ WARNING: possible recursive locking detected 6.10.0-rc6-00452-ga4d0275fa660-dirty #79 Not tainted -------------------------------------------- bash/710 is trying to acquire lock: ffffffff8f0a7850 (&h->resize_lock){+.+.}-{3:3}, at: demote_store+0x244/0x460 but task is already holding lock: ffffffff8f0a6f48 (&h->resize_lock){+.+.}-{3:3}, at: demote_store+0xae/0x460 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&h->resize_lock); lock(&h->resize_lock); *** DEADLOCK *** May be due to missing lock nesting notation 4 locks held by bash/710: #0: ffff8f118439c3f0 (sb_writers#5){.+.+}-{0:0}, at: ksys_write+0x64/0xe0 #1: ffff8f11893b9e88 (&of->mutex#2){+.+.}-{3:3}, at: kernfs_fop_write_iter+0xf8/0x1d0 #2: ffff8f1183dc4428 (kn->active#98){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x100/0x1d0 #3: ffffffff8f0a6f48 (&h->resize_lock){+.+.}-{3:3}, at: demote_store+0xae/0x460 stack backtrace: CPU: 3 PID: 710 Comm: bash Not tainted 6.10.0-rc6-00452-ga4d0275fa660-dirty #79 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x68/0xa0 __lock_acquire+0x10f2/0x1ca0 lock_acquire+0xbe/0x2d0 __mutex_lock+0x6d/0x400 demote_store+0x244/0x460 kernfs_fop_write_iter+0x12c/0x1d0 vfs_write+0x380/0x540 ksys_write+0x64/0xe0 do_syscall_64+0xb9/0x1d0 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fa61db14887 RSP: 002b:00007ffc56c48358 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007fa61db14887 RDX: 0000000000000002 RSI: 000055a030050220 RDI: 0000000000000001 RBP: 000055a030050220 R08: 00007fa61dbd1460 R09: 000000007fffffff R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002 R13: 00007fa61dc1b780 R14: 00007fa61dc17600 R15: 00007fa61dc16a00 </TASK> Lockdep considers this an AA deadlock because the different resize_lock mutexes reside in the same lockdep class, but this is a false positive. Place them in distinct classes to avoid these warnings. Link: https://lkml.kernel.org/r/[email protected] Fixes: 8531fc6 ("hugetlb: add hugetlb demote page support") Signed-off-by: Miaohe Lin <[email protected]> Acked-by: Muchun Song <[email protected]> Cc: <[email protected]> Signed-off-by: Andrew Morton <[email protected]>
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Armv7-A is becoming less popular given how cheap 64-bit chips are getting; however, we will have embedded 32-bit ARM around us for at least a decade, likely more. It is one of the key kernel architectures, too; and like x86, it is a good idea to support at least one 32-bit architecture to widen our tests and uncover possible issues etc.
Linux arm targets with official Ubuntu binutils etc. support:
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