On Mon, Nov 20, 2017 at 11:33 PM, Ingo Molnar <mi...@kernel.org> wrote: > > * Andy Lutomirski <l...@kernel.org> wrote: > >> This sets up stack switching, including for SYSCALL. I think it's >> in decent shape. >> >> Known issues: >> - KASAN is likely to be busted. This could be fixed either by teaching >> KASAN that cpu_entry_area contains valid stacks (I have no clue how >> to go about doing this) or by rigging up the IST entry code to switch >> RSP to point to the direct-mapped copy of the stacks before calling >> into non-KASAN-excluded C code. >> >> - 32-bit kernels are failing the sigreturn_32 test. But they're also >> failing without the patches, so I'm not sure this is a bug in the >> series per se. Needs further investigation. (Off the top of my head, >> this could be further fallout from Thomas's IDT rework.) >> >> - I think we're going to want a way to turn the stack switching on and >> off either at boot time or at runtime. It should be fairly >> straightforward >> to make it work. >> >> - I think the ORC unwinder isn't so good at dealing with stack overflows. >> It bails too early (I think), resulting in lots of ? entries. This >> isn't a regression with this series -- it's just something that could >> be improved. > > Another problem I just found: IRQ tracing appears busted on 64-bit kernels - > with > lockdep enabled I get this boot warning: > > [ 4.309026] WARNING: CPU: 10 PID: 222 at kernel/locking/lockdep.c:3924 > check_flags.part.45+0x1a5/0x1b0 > ... > [ 4.309026] possible reason: unannotated irqs-off. > > That's on a x86-64 defconfig-ish kernel with CONFIG_PROVE_LOCKING=y, running > on an > AMD system. Full splat below. > > Thanks, > > Ingo > > [ 4.272197] LVT offset 0 assigned for vector 0x400 > [ 4.278486] perf: AMD IBS detected (0x000000ff) > [ 4.284786] kvm: Nested Virtualization enabled > [ 4.289447] kvm: Nested Paging enabled > [ 4.308496] DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled) > [ 4.308512] ------------[ cut here ]------------ > [ 4.309026] WARNING: CPU: 10 PID: 222 at kernel/locking/lockdep.c:3924 > check_flags.part.45+0x1a5/0x1b0 > [ 4.309026] Modules linked in: > [ 4.309026] CPU: 10 PID: 222 Comm: modprobe Not tainted > 4.14.0-01345-g9490674-dirty #1 > [ 4.309026] Hardware name: Supermicro H8DG6/H8DGi/H8DG6/H8DGi, BIOS 2.0b > 03/01/2012 > [ 4.309026] task: ffff880814b08000 task.stack: ffffc90007dcc000 > [ 4.309026] RIP: 0010:check_flags.part.45+0x1a5/0x1b0 > [ 4.309026] RSP: 0018:ffffc90007dcfeb0 EFLAGS: 00010082 > [ 4.309026] RAX: 000000000000002e RBX: ffff880814b08000 RCX: > 0000000000000000 > [ 4.309026] RDX: 0000000000000000 RSI: 0000000000000001 RDI: > ffffffff81152e76 > [ 4.309026] RBP: 0000000000000000 R08: 0000000000000001 R09: > 0000000000000000 > [ 4.309026] R10: 0000000000000000 R11: 0000000000000000 R12: > 0000000000000000 > [ 4.309026] R13: 0000000000000000 R14: 0000000000000001 R15: > 0000000000000000 > [ 4.309026] FS: 0000000000000000(0000) GS:ffff880817c80000(0000) > knlGS:0000000000000000 > [ 4.309026] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 4.309026] CR2: 00007f8badc39218 CR3: 000000081584b000 CR4: > 00000000000406e0 > [ 4.309026] Call Trace: > [ 4.309026] lock_acquire+0x11a/0x1d0 > [ 4.309026] vtime_user_exit+0x3c/0xa0 > [ 4.309026] ? __context_tracking_exit.part.4+0x45/0x130 > [ 4.309026] __context_tracking_exit.part.4+0x45/0x130 > [ 4.309026] do_syscall_64+0x13f/0x220 > [ 4.309026] entry_SYSCALL64_slow_path+0x25/0x25
I'm not reproducing this. On quick inspection, the only potential issue I see is that native_gs_load_index is missing IRQ tracing annotations, but I don't see why this series would have any particular effect on that. Do you see it on my latest tree? --Andy
