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From: | Yi Min Zhao |
Subject: | Re: [Qemu-devel] [PATCH 4/4] s390x/pci: add iommu replay callback |
Date: | Tue, 29 Aug 2017 16:26:10 +0800 |
User-agent: | Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 |
在 2017/8/29 下午4:07, Cornelia Huck 写道:
The iommu replay function is originally introduced for vfio. I think they want to re-build the existing mappings because vfio has a copy of mappings in kernel. For our case,[Restored cc:s. Please remember to do reply-all.] On Tue, 29 Aug 2017 12:46:51 +0800 Yi Min Zhao <address@hidden> 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 <address@hidden> 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 <address@hidden> Reviewed-by: Halil Pasic <address@hidden> Signed-off-by: Yi Min Zhao <address@hidden> --- 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?)
the mappings would be cleanup when a pci device unplugged, and new mappingswould be created when a pci device plugged. I think replay only can happen during
vfio-pci device migration.
My understanding is virtio-pci doesn't need replay. All mappings of any pci device are existing in guest memory. Once the mappings is built, all of them could be migrated along with the guestIn 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?)
system. But I might misunderstand it. Please correct me.
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