1. 03 Sep, 2020 38 commits
  2. 26 Aug, 2020 2 commits
    • Greg Kroah-Hartman's avatar
      f6d5cb9e
    • Will Deacon's avatar
      KVM: arm64: Only reschedule if MMU_NOTIFIER_RANGE_BLOCKABLE is not set · 0f090712
      Will Deacon authored
      commit b5331379 upstream.
      
      When an MMU notifier call results in unmapping a range that spans multiple
      PGDs, we end up calling into cond_resched_lock() when crossing a PGD boundary,
      since this avoids running into RCU stalls during VM teardown. Unfortunately,
      if the VM is destroyed as a result of OOM, then blocking is not permitted
      and the call to the scheduler triggers the following BUG():
      
       | BUG: sleeping function called from invalid context at arch/arm64/kvm/mmu.c:394
       | in_atomic(): 1, irqs_disabled(): 0, non_block: 1, pid: 36, name: oom_reaper
       | INFO: lockdep is turned off.
       | CPU: 3 PID: 36 Comm: oom_reaper Not tainted 5.8.0 #1
       | Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
       | Call trace:
       |  dump_backtrace+0x0/0x284
       |  show_stack+0x1c/0x28
       |  dump_stack+0xf0/0x1a4
       |  ___might_sleep+0x2bc/0x2cc
       |  unmap_stage2_range+0x160/0x1ac
       |  kvm_unmap_hva_range+0x1a0/0x1c8
       |  kvm_mmu_notifier_invalidate_range_start+0x8c/0xf8
       |  __mmu_notifier_invalidate_range_start+0x218/0x31c
       |  mmu_notifier_invalidate_range_start_nonblock+0x78/0xb0
       |  __oom_reap_task_mm+0x128/0x268
       |  oom_reap_task+0xac/0x298
       |  oom_reaper+0x178/0x17c
       |  kthread+0x1e4/0x1fc
       |  ret_from_fork+0x10/0x30
      
      Use the new 'flags' argument to kvm_unmap_hva_range() to ensure that we
      only reschedule if MMU_NOTIFIER_RANGE_BLOCKABLE is set in the notifier
      flags.
      
      Cc: <stable@vger.kernel.org>
      Fixes: 8b3405e3 ("kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd")
      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>
      Message-Id: <20200811102725.7121-3-will@kernel.org>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      [will: Backport to 4.19; use 'blockable' instead of non-existent MMU_NOTIFIER_RANGE_BLOCKABLE flag]
      Signed-off-by: default avatarWill Deacon <will@kernel.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      0f090712