From 9bb38019942c2f3f44b98f5830e369faec701e55 Mon Sep 17 00:00:00 2001 From: "Dr. David Alan Gilbert" Date: Mon, 12 Mar 2018 17:21:10 +0000 Subject: vhost+postcopy: Send address back to qemu MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We need a better way, but at the moment we need the address of the mappings sent back to qemu so it can interpret the messages on the userfaultfd it reads. This is done as a 3 stage set: QEMU -> client set_mem_table mmap stuff, get addresses client -> qemu here are the addresses qemu -> client OK - now you can use them That ensures that qemu has registered the new addresses in it's userfault code before the client starts accessing them. Note: We don't ask for the default 'ack' reply since we've got our own. Signed-off-by: Dr. David Alan Gilbert Reviewed-by: Marc-André Lureau Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- contrib/libvhost-user/libvhost-user.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) (limited to 'contrib/libvhost-user/libvhost-user.c') diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c index 7c8cd5878e..6314549b65 100644 --- a/contrib/libvhost-user/libvhost-user.c +++ b/contrib/libvhost-user/libvhost-user.c @@ -491,10 +491,32 @@ vu_set_mem_table_exec_postcopy(VuDev *dev, VhostUserMsg *vmsg) dev_region->mmap_addr); } + /* Return the address to QEMU so that it can translate the ufd + * fault addresses back. + */ + msg_region->userspace_addr = (uintptr_t)(mmap_addr + + dev_region->mmap_offset); close(vmsg->fds[i]); } - /* TODO: Get address back to QEMU */ + /* Send the message back to qemu with the addresses filled in */ + vmsg->fd_num = 0; + if (!vu_message_write(dev, dev->sock, vmsg)) { + vu_panic(dev, "failed to respond to set-mem-table for postcopy"); + return false; + } + + /* Wait for QEMU to confirm that it's registered the handler for the + * faults. + */ + if (!vu_message_read(dev, dev->sock, vmsg) || + vmsg->size != sizeof(vmsg->payload.u64) || + vmsg->payload.u64 != 0) { + vu_panic(dev, "failed to receive valid ack for postcopy set-mem-table"); + return false; + } + + /* OK, now we can go and register the memory and generate faults */ for (i = 0; i < dev->nregions; i++) { VuDevRegion *dev_region = &dev->regions[i]; #ifdef UFFDIO_REGISTER -- cgit v1.2.3