From: Jason Wang <jasow...@redhat.com> Date: Mon, 13 May 2019 01:27:45 -0400
> Vhost log dirty pages directly to a userspace bitmap through GUP and > kmap_atomic() since kernel doesn't have a set_bit_to_user() > helper. This will cause issues for the arch that has virtually tagged > caches. The way to fix is to keep using userspace virtual > address. Fortunately, futex has arch_futex_atomic_op_inuser() which > could be used for setting a bit to user. > > Note there're several cases that futex helper can fail e.g a page > fault or the arch that doesn't have the support. For those cases, a > simplified get_user()/put_user() pair protected by a global mutex is > provided as a fallback. The fallback may lead false positive that > userspace may see more dirty pages. > > Cc: Christoph Hellwig <h...@infradead.org> > Cc: James Bottomley <james.bottom...@hansenpartnership.com> > Cc: Andrea Arcangeli <aarca...@redhat.com> > Cc: Thomas Gleixner <t...@linutronix.de> > Cc: Ingo Molnar <mi...@redhat.com> > Cc: Peter Zijlstra <pet...@infradead.org> > Cc: Darren Hart <dvh...@infradead.org> > Fixes: 3a4d5c94e9593 ("vhost_net: a kernel-level virtio server") > Signed-off-by: Jason Wang <jasow...@redhat.com> I want to see a review from Michael for this change before applying. _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization