2017-10-06 09:33+0800, Boqun Feng: > On Tue, Oct 03, 2017 at 02:11:08PM +0000, Paolo Bonzini wrote: > > I'd prefer a slight change in subject and topic: > > > > ------- 8< -------- > > Subject: [PATCH] kvm/x86: Avoid async PF preempting the kernel incorrectly > > > > Currently, in PREEMPT_COUNT=n kernel, kvm_async_pf_task_wait() could call > > schedule() to reschedule in some cases. This could result in > > accidentally ending the current RCU read-side critical section early, > > causing random memory corruption in the guest, or otherwise preempting > > the currently running task inside between preempt_disable and > > preempt_enable. > > > > The difficulty to handle this well is because we don't know whether an > > async PF delivered in a preemptible section or RCU read-side critical section > > for PREEMPT_COUNT=n, since preempt_disable()/enable() and rcu_read_lock/unlock() > > are both no-ops in that case. > > > > To cure this, we treat any async PF interrupting a kernel context as one > > that cannot be preempted, preventing kvm_async_pf_task_wait() from choosing > > the schedule() path in that case. > > > > To do so, a second parameter for kvm_async_pf_task_wait() is introduced, > > so that we know whether it's called from a context interrupting the > > kernel, and the parameter is set properly in all the callsites. > > > > Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> > > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > > Cc: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> > > Cc: stable@xxxxxxxxxxxxxxx > > Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx> > > ------- 8< -------- > > > > It's more concise and accurate now! > > Learned a lot from your modification of commit messages, thanks! Applied with the updated commit message, thanks.
