[Restored cc:s. Please remember to do reply-all.]
On Tue, 29 Aug 2017 12:46:51 +0800
Yi Min Zhao <zyi...@linux.vnet.ibm.com> wrote:
> 在 2017/8/28 下午11:57, Cornelia Huck 写道:
> > On Mon, 28 Aug 2017 10:04:47 +0200
> > Yi Min Zhao <zyi...@linux.vnet.ibm.com> wrote:
> >
> >> Let's introduce iommu replay callback for s390 pci iommu memory region.
> >> Currently we don't need any dma mapping replay. So let it return
> >> directly. This implementation will avoid meaningless loops calling
> >> translation callback.
> >>
> >> Reviewed-by: Pierre Morel <pmo...@linux.vnet.ibm.com>
> >> Reviewed-by: Halil Pasic <pa...@linux.vnet.ibm.com>
> >> Signed-off-by: Yi Min Zhao <zyi...@linux.vnet.ibm.com>
> >> ---
> >> hw/s390x/s390-pci-bus.c | 8 ++++++++
> >> 1 file changed, 8 insertions(+)
> >>
> >> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
> >> index 9e1f7ff5c5..359509ccea 100644
> >> --- a/hw/s390x/s390-pci-bus.c
> >> +++ b/hw/s390x/s390-pci-bus.c
> >> @@ -407,6 +407,13 @@ static IOMMUTLBEntry
> >> s390_translate_iommu(IOMMUMemoryRegion *mr, hwaddr addr,
> >> return ret;
> >> }
> >>
> >> +static void s390_pci_iommu_replay(IOMMUMemoryRegion *iommu,
> >> + IOMMUNotifier *notifier)
> >> +{
> >> + /* we don't need iommu replay currently */
> > This really needs to be heavier on the _why_. My guess is that anything
> > which would require replay goes through the rpcit instruction?
> My understanding is:
> Our arch is different from others. Each pci device has its own iommu, not
> like other archs' implementation. So currently there must be no existing
> mappings belonging to any newly plugged pci device whose iommu doesn't
> have any mapping at the time.
So please put that explanation into the function. (Also, "currently"?
Are we expecting it to change?)
> In addition, it's also due to vfio blocking migration. If vfio-pci supports
> migration in future, we could implement iommu replay by that time.
That's not an argument: This is the base zpci support, it should not
depend on the supported devices and what they do. (What's the status of
virtio-pci, btw? Does it work with your patches applied, or is there
still more to be done?)
