Hi David,
On 12/05/2017 06:41 PM, Dr. David Alan Gilbert wrote:
Hi,
Since I'm reworking the memory map update code I've been
trying to test it with hot adding RAM; but even on upstream
I'm finding that hot adding RAM causes the guest to stop passing
packets with vhost-user-bridge; have either of you seen the same
thing?
No, I have never tried this.
I'm doing:
./tests/vhost-user-bridge -u /tmp/vubrsrc.sock
$QEMU -enable-kvm -m 1G,maxmem=2G,slots=4 -smp 2 -object
memory-backend-file,id=mem,size=1G,mem-path=/dev/shm,share=on -numa
node,memdev=mem -mem-prealloc -trace events=vhost-trace-file -chardev
socket,id=char0,path=/tmp/vubrsrc.sock -netdev
type=vhost-user,id=mynet1,chardev=char0,vhostforce -device
virtio-net-pci,netdev=mynet1 $IMAGE -net none
(with a f27 guest) and then doing:
(qemu) object_add memory-backend-file,id=mem1,size=256M,mem-path=/dev/shm
(qemu) device_add pc-dimm,id=dimm1,memdev=mem1
but then not getting any responses inside the guest.
I can see the code sending another set-mem-table with the
extra chunk of RAM and fd, and I think I can see the bridge
mapping it.
I think there are at least two problems.
The first one is that vhost-user-bridge does not support vhost-user
protocol's reply-ack feature. So when QEMU sends the requests, it cannot
know whether/when it has been handled by the backend.
It had been fixed by sending a GET_FEATURE requests to be sure the
SET_MEM_TABLE was handled, as messages are processed in order. The problem
is that it caused some test failures when using TCG, so it got
reverted.
The initial fix:
commit 28ed5ef16384f12500abd3647973ee21b03cbe23
Author: Prerna Saxena <address@hidden>
Date: Fri Aug 5 03:53:51 2016 -0700
vhost-user: Attempt to fix a race with set_mem_table.
The revert:
commit 94c9cb31c04737f86be29afefbff401cd23bc24d
Author: Michael S. Tsirkin <address@hidden>
Date: Mon Aug 15 16:35:24 2016 +0300
Revert "vhost-user: Attempt to fix a race with set_mem_table."