From: Michael Roth <mdroth@linux.vnet.ibm.com>
To: Alexey Kardashevskiy <aik@ozlabs.ru>, qemu-devel@nongnu.org
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
David Gibson <david@gibson.dropbear.id.au>
Subject: Re: virtio,iommu_platform=on
Date: Tue, 12 Nov 2019 23:54:57 -0600 [thread overview]
Message-ID: <157362449788.24851.9129567746458175944@sif> (raw)
In-Reply-To: <17da2769-1999-a0a3-590d-9f9bc6a9adc3@ozlabs.ru>
Quoting Alexey Kardashevskiy (2019-11-11 21:53:49)
> Hi!
>
> I am enabling IOMMU for virtio in the pseries firmware (SLOF) and seeing
> problems, one of them is SLOF does SCSI bus scan, then it stops the
> virtio-scsi by clearing MMIO|IO|BUSMASTER from PCI_COMMAND (as SLOF
> stopped using the devices) and when this happens, I see unassigned
> memory access (see below) which happens because disabling busmaster
> disables IOMMU and QEMU cannot access the rings to do some shutdown. And
> when this happens, the device does not come back even if SLOF re-enables it.
>
> Hacking SLOF to not clear BUSMASTER makes virtio-scsi work but it is
> hardly a right fix.
I hit the same issue enabling IOMMU for virtio-blk using this branch:
https://github.com/mdroth/SLOF/commits/virtio-iommu
I just sent a tentative fix for QEMU as:
"virtio-pci: disable vring processing when bus-mastering is disabled"
It's an RFC since piggy-backing off dev->broken seems a bit hacky, but
it seems to fix the issue at least.
BTW, the SLOF branch above needs cleanup, but it's booting guests okay
and I was planning to post this week. Where are you at on yours? Maybe
we should sync up...
next prev parent reply other threads:[~2019-11-13 5:56 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-12 3:53 virtio,iommu_platform=on Alexey Kardashevskiy
2019-11-12 7:08 ` virtio,iommu_platform=on Michael S. Tsirkin
2019-11-13 4:44 ` virtio,iommu_platform=on Alexey Kardashevskiy
2019-11-13 10:00 ` virtio,iommu_platform=on Michael S. Tsirkin
2019-11-13 22:58 ` virtio,iommu_platform=on Alexey Kardashevskiy
2019-11-14 8:42 ` virtio,iommu_platform=on Michael S. Tsirkin
2019-11-15 1:43 ` virtio,iommu_platform=on Alexey Kardashevskiy
2019-11-12 9:06 ` virtio,iommu_platform=on Laszlo Ersek
2019-11-13 4:54 ` virtio,iommu_platform=on Alexey Kardashevskiy
2019-11-13 5:54 ` Michael Roth [this message]
2019-11-13 6:23 ` virtio,iommu_platform=on Alexey Kardashevskiy
2019-11-13 6:35 ` virtio,iommu_platform=on Alexey Kardashevskiy
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