Re: [Qemu-devel] [RFC 0/2] Fix QEMU crash during memory hotplug with vhost=on

[Michael S. Tsirkin]

On Wed, Jun 03, 2015 at 02:22:35PM +0200, Igor Mammedov wrote:
> When more than ~50 pc-dimm devices are hotplugged with
> vhost enabled, QEMU will assert in vhost vhost_commit()
> due to backend refusing to accept too many memory ranges.
> 
> Series introduces Reserved HVA MemoryRegion container
> where all hotplugged memory is remapped and passes
> the single container range to vhost instead of multiple
> memory ranges for each hotlugged pc-dimm device.
> 
> It's alternative approach to increasing backend supported
> memory regions limit since what I've come up with
> backend side approach is quite a bit more code so far.
> 
> With this approach it would be possible to extend it to
> initial memory later and provide a single range for all
> RAM to vhost, which should speed up its hot-path by replacing
> current GPA<->HVA lookup loop with offset calculation.

I'm a bit too busy for a thorough review so it'll take
a bit of time. From a quick look, it's nice.

Acked-by: Michael S. Tsirkin <address@hidden>


> Igor Mammedov (2):
>   memory: introduce MemoryRegion container with reserved HVA range
>   pc: fix QEMU crashing when more than ~50 memory hotplugged
> 
>  exec.c                    | 13 +++++++++++
>  hw/i386/pc.c              |  4 ++--
>  hw/virtio/vhost.c         | 15 ++++++++++---
>  include/exec/cpu-common.h |  1 +
>  include/exec/memory.h     | 42 ++++++++++++++++++++++++++++++++++--
>  memory.c                  | 55 
> +++++++++++++++++++++++++++++++++++++++++++++++
>  6 files changed, 123 insertions(+), 7 deletions(-)
> 
> -- 
> 1.8.3.1