Re: [Qemu-devel] [PATCH for-2.10 0/5] x86/vIOMMU: move init back to machine init phase

[Michael S. Tsirkin]

On Fri, Mar 31, 2017 at 03:36:28PM +0800, Peter Xu wrote:
> At the very beginning, the x86 vIOMMUs are created via "-M iommu=on".
> We moved one step further a year ago to have the vIOMMUs just like a
> general device, so that we can init them with far more specific
> parameters with "-device" interface.
> 
> However, gradually we found that problem starts to occur due to this.
> The main issue is that the DMA address space of any PCI device is
> postponed to be init after device realization, while some devices'
> realizations would depend on this address space. That looks like a
> dead lock. We have patches and solutions for different single problem,
> but, maybe it's time we can consider to solve the root cause this
> time, of course after 2.9 release.
> 
> This series tries to solve the root cause, and move vIOMMU inits back
> to machine init for x86 platforms. Then, we'll have solid DMA address
> space for each device even during realization.
> 
> Please kindly review. Thanks.

I think it's a clean way to do it at a high level.
However I would like to set a tag in the class
rather than listing specific devices.
Also, init order should be consistent for all machines
not just q35.



> Peter Xu (5):
>   QemuOpts: introduce qemu_opts_extract()
>   util: export device_init_func()
>   util: propagate error for device_func_init()
>   q35: init vIOMMU during machine init
>   pci: move dma_as init back to bus realize
> 
>  hw/pci-host/q35.c        | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  hw/pci/pci.c             | 21 +--------------------
>  include/hw/pci/pci_bus.h |  2 --
>  include/qemu-common.h    |  1 +
>  include/qemu/option.h    |  2 ++
>  include/sysemu/sysemu.h  |  1 -
>  util/qemu-option.c       | 24 ++++++++++++++++++++++++
>  vl.c                     |  9 ++-------
>  8 files changed, 75 insertions(+), 30 deletions(-)
> 
> -- 
> 2.7.4