From: David Hildenbrand <david@redhat.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Marek Kedzierski <mkedzier@redhat.com>,
Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
Wei Yang <richard.weiyang@linux.alibaba.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
qemu-devel@nongnu.org, Peter Xu <peterx@redhat.com>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
Auger Eric <eric.auger@redhat.com>,
Pankaj Gupta <pankaj.gupta@cloud.ionos.com>,
teawater <teawaterz@linux.alibaba.com>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Igor Mammedov <imammedo@redhat.com>
Subject: Re: [PATCH v4 11/11] vfio: Disable only uncoordinated discards
Date: Thu, 14 Jan 2021 17:19:02 +0100 [thread overview]
Message-ID: <fce51f31-6cba-681c-e61e-2ff0c018c7bf@redhat.com> (raw)
In-Reply-To: <20210113165708.45a8701c@omen.home.shazbot.org>
On 14.01.21 00:57, Alex Williamson wrote:
> On Thu, 7 Jan 2021 14:34:23 +0100
> David Hildenbrand <david@redhat.com> wrote:
>
>> We support coordinated discarding of RAM using the RamDiscardMgr. Let's
>> unlock support for coordinated discards, keeping uncoordinated discards
>> (e.g., via virtio-balloon) disabled.
>>
>> This unlocks virtio-mem + vfio. Note that vfio used via "nvme://" by the
>> block layer has to be implemented/unlocked separately. For now,
>> virtio-mem only supports x86-64 - spapr IOMMUs are not tested/affected.
>
> I think SPAPR always uses a vIOMMU, but I won't claim to understand it.
I heard about that, but I also know that they are using virtio-balloon.
Theoretically, virtio-balloon does currently not support vIOMMUs
(iommu=on results in the balloon device essentially being disable).
> Is there anything other than testing that restricts it to x86-64? ARM
I am not aware, but well, I guess we'll learn as we go/unlock virtio-mem
on these architectures.
Jonathan is trying to enable arm64 support for virtio-mem. I asked him
to test vfio.
I'll have to cleanup my s390x prototype and find a machine to test with
vfio.
> and S390 will use the same type1 IOMMU backend as far as vfio support
> is concerned. Should we do something more than put it in a commit log
> if we really want to prevent it elsewhere? Thanks,
I think it should be sufficient to have it in the logs for now. I'll be
involved when unlocking virtio-mem on other archs and will request to
test vfio. In case we find issues, we should try fixing them first
(instead of fencing it / bailing out).
Obviously, this won't stop other RamDiscardMgr users from popping up,
but I guess we'll stumble over that as well.
--
Thanks,
David / dhildenb
prev parent reply other threads:[~2021-01-14 16:36 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-07 13:34 [PATCH v4 00/11] virtio-mem: vfio support David Hildenbrand
2021-01-07 13:34 ` [PATCH v4 01/11] memory: Introduce RamDiscardMgr for RAM memory regions David Hildenbrand
2021-01-07 13:34 ` [PATCH v4 02/11] virtio-mem: Factor out traversing unplugged ranges David Hildenbrand
2021-01-07 13:34 ` [PATCH v4 03/11] virtio-mem: Implement RamDiscardMgr interface David Hildenbrand
2021-01-07 13:34 ` [PATCH v4 04/11] vfio: Support for RamDiscardMgr in the !vIOMMU case David Hildenbrand
2021-01-13 23:27 ` Alex Williamson
2021-01-14 15:54 ` David Hildenbrand
2021-01-14 15:57 ` David Hildenbrand
2021-01-15 10:27 ` David Hildenbrand
2021-01-07 13:34 ` [PATCH v4 05/11] vfio: Query and store the maximum number of possible DMA mappings David Hildenbrand
2021-01-13 23:30 ` Alex Williamson
2021-01-07 13:34 ` [PATCH v4 06/11] vfio: Sanity check maximum number of DMA mappings with RamDiscardMgr David Hildenbrand
2021-01-13 23:34 ` Alex Williamson
2021-01-14 15:59 ` David Hildenbrand
2021-01-07 13:34 ` [PATCH v4 07/11] vfio: Support for RamDiscardMgr in the vIOMMU case David Hildenbrand
2021-01-07 13:34 ` [PATCH v4 08/11] softmmu/physmem: Don't use atomic operations in ram_block_discard_(disable|require) David Hildenbrand
2021-01-07 13:34 ` [PATCH v4 09/11] softmmu/physmem: Extend ram_block_discard_(require|disable) by two discard types David Hildenbrand
2021-01-07 13:34 ` [PATCH v4 10/11] virtio-mem: Require only coordinated discards David Hildenbrand
2021-01-07 13:34 ` [PATCH v4 11/11] vfio: Disable only uncoordinated discards David Hildenbrand
2021-01-13 23:57 ` Alex Williamson
2021-01-14 16:19 ` David Hildenbrand [this message]
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