On 2019/5/14 上午12:42, David Miller wrote:
From: Jason Wang <jasowang@xxxxxxxxxx> Date: Mon, 13 May 2019 01:27:45 -0400Vhost 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 <hch@xxxxxxxxxxxxx> Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Darren Hart <dvhart@xxxxxxxxxxxxx> Fixes: 3a4d5c94e9593 ("vhost_net: a kernel-level virtio server") Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>I want to see a review from Michael for this change before applying.
No problem, since kbuild spotted an issue. Let me post V2. Thanks
