1. 03 Sep, 2020 37 commits
  2. 26 Aug, 2020 3 commits
    • Greg Kroah-Hartman's avatar
      c6a15d15
    • Will Deacon's avatar
      KVM: arm/arm64: Don't reschedule in unmap_stage2_range() · c0ca97bc
      Will Deacon authored
      Upstream commits fdfe7cbd ("KVM: Pass MMU notifier range flags to
      kvm_unmap_hva_range()") and b5331379 ("KVM: arm64: Only reschedule
      if MMU_NOTIFIER_RANGE_BLOCKABLE is not set") fix a "sleeping from invalid
      context" BUG caused by unmap_stage2_range() attempting to reschedule when
      called on the OOM path.
      
      Unfortunately, these patches rely on the MMU notifier callback being
      passed knowledge about whether or not blocking is permitted, which was
      introduced in 4.19. Rather than backport this considerable amount of
      infrastructure just for KVM on arm, instead just remove the conditional
      reschedule.
      
      Cc: <stable@vger.kernel.org> # v4.9 only
      Cc: Marc Zyngier <maz@kernel.org>
      Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
      Cc: James Morse <james.morse@arm.com>
      Signed-off-by: default avatarWill Deacon <will@kernel.org>
      Acked-by: default avatarMarc Zyngier <maz@kernel.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      c0ca97bc
    • Juergen Gross's avatar
      xen: don't reschedule in preemption off sections · 606c6eb9
      Juergen Gross authored
      For support of long running hypercalls xen_maybe_preempt_hcall() is
      calling cond_resched() in case a hypercall marked as preemptible has
      been interrupted.
      
      Normally this is no problem, as only hypercalls done via some ioctl()s
      are marked to be preemptible. In rare cases when during such a
      preemptible hypercall an interrupt occurs and any softirq action is
      started from irq_exit(), a further hypercall issued by the softirq
      handler will be regarded to be preemptible, too. This might lead to
      rescheduling in spite of the softirq handler potentially having set
      preempt_disable(), leading to splats like:
      
      BUG: sleeping function called from invalid context at drivers/xen/preempt.c:37
      in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 20775, name: xl
      INFO: lockdep is turned off.
      CPU: 1 PID: 20775 Comm: xl Tainted: G D W 5.4.46-1_prgmr_debug.el7.x86_64 #1
      Call Trace:
      <IRQ>
      dump_stack+0x8f/0xd0
      ___might_sleep.cold.76+0xb2/0x103
      xen_maybe_preempt_hcall+0x48/0x70
      xen_do_hypervisor_callback+0x37/0x40
      RIP: e030:xen_hypercall_xen_version+0xa/0x20
      Code: ...
      RSP: e02b:ffffc900400dcc30 EFLAGS: 00000246
      RAX: 000000000004000d RBX: 0000000000000200 RCX: ffffffff8100122a
      RDX: ffff88812e788000 RSI: 0000000000000000 RDI: 0000000000000000
      RBP: ffffffff83ee3ad0 R08: 0000000000000001 R09: 0000000000000001
      R10: 0000000000000000 R11: 0000000000000246 R12: ffff8881824aa0b0
      R13: 0000000865496000 R14: 0000000865496000 R15: ffff88815d040000
      ? xen_hypercall_xen_version+0xa/0x20
      ? xen_force_evtchn_callback+0x9/0x10
      ? check_events+0x12/0x20
      ? xen_restore_fl_direct+0x1f/0x20
      ? _raw_spin_unlock_irqrestore+0x53/0x60
      ? debug_dma_sync_single_for_cpu+0x91/0xc0
      ? _raw_spin_unlock_irqrestore+0x53/0x60
      ? xen_swiotlb_sync_single_for_cpu+0x3d/0x140
      ? mlx4_en_process_rx_cq+0x6b6/0x1110 [mlx4_en]
      ? mlx4_en_poll_rx_cq+0x64/0x100 [mlx4_en]
      ? net_rx_action+0x151/0x4a0
      ? __do_softirq+0xed/0x55b
      ? irq_exit+0xea/0x100
      ? xen_evtchn_do_upcall+0x2c/0x40
      ? xen_do_hypervisor_callback+0x29/0x40
      </IRQ>
      ? xen_hypercall_domctl+0xa/0x20
      ? xen_hypercall_domctl+0x8/0x20
      ? privcmd_ioctl+0x221/0x990 [xen_privcmd]
      ? do_vfs_ioctl+0xa5/0x6f0
      ? ksys_ioctl+0x60/0x90
      ? trace_hardirqs_off_thunk+0x1a/0x20
      ? __x64_sys_ioctl+0x16/0x20
      ? do_syscall_64+0x62/0x250
      ? entry_SYSCALL_64_after_hwframe+0x49/0xbe
      
      Fix that by testing preempt_count() before calling cond_resched().
      
      In kernel 5.8 this can't happen any more due to the entry code rework
      (more than 100 patches, so not a candidate for backporting).
      
      The issue was introduced in kernel 4.3, so this patch should go into
      all stable kernels in [4.3 ... 5.7].
      Reported-by: default avatarSarah Newman <srn@prgmr.com>
      Fixes: 0fa2f5cb ("sched/preempt, xen: Use need_resched() instead of should_resched()")
      Cc: Sarah Newman <srn@prgmr.com>
      Cc: stable@vger.kernel.org
      Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
      Tested-by: default avatarChris Brannon <cmb@prgmr.com>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      606c6eb9