From: Thiago Jung Bauermann <bauerman@linux.ibm.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Mike Anderson <andmike@linux.ibm.com>,
Michael Roth <mdroth@linux.vnet.ibm.com>,
Jean-Philippe Brucker <jean-philippe.brucker@arm.com>,
Jason Wang <jasowang@redhat.com>,
Alexey Kardashevskiy <aik@linux.ibm.com>,
Ram Pai <linuxram@us.ibm.com>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org,
Christoph Hellwig <hch@lst.de>,
David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted
Date: Mon, 15 Jul 2019 19:03:03 -0300 [thread overview]
Message-ID: <8736j7neg8.fsf@morokweng.localdomain> (raw)
In-Reply-To: <20190715163453-mutt-send-email-mst@kernel.org>
Michael S. Tsirkin <mst@redhat.com> writes:
> On Mon, Jul 15, 2019 at 05:29:06PM -0300, Thiago Jung Bauermann wrote:
>>
>> Michael S. Tsirkin <mst@redhat.com> writes:
>>
>> > On Sun, Jul 14, 2019 at 02:51:18AM -0300, Thiago Jung Bauermann wrote:
>> >>
>> >>
>> >> Michael S. Tsirkin <mst@redhat.com> writes:
>> >>
>> >> > So this is what I would call this option:
>> >> >
>> >> > VIRTIO_F_ACCESS_PLATFORM_IDENTITY_ADDRESS
>> >> >
>> >> > and the explanation should state that all device
>> >> > addresses are translated by the platform to identical
>> >> > addresses.
>> >> >
>> >> > In fact this option then becomes more, not less restrictive
>> >> > than VIRTIO_F_ACCESS_PLATFORM - it's a promise
>> >> > by guest to only create identity mappings,
>> >> > and only before driver_ok is set.
>> >> > This option then would always be negotiated together with
>> >> > VIRTIO_F_ACCESS_PLATFORM.
>> >> >
>> >> > Host then must verify that
>> >> > 1. full 1:1 mappings are created before driver_ok
>> >> > or can we make sure this happens before features_ok?
>> >> > that would be ideal as we could require that features_ok fails
>> >> > 2. mappings are not modified between driver_ok and reset
>> >> > i guess attempts to change them will fail -
>> >> > possibly by causing a guest crash
>> >> > or some other kind of platform-specific error
>> >>
>> >> I think VIRTIO_F_ACCESS_PLATFORM_IDENTITY_ADDRESS is good, but requiring
>> >> it to be accompanied by ACCESS_PLATFORM can be a problem. One reason is
>> >> SLOF as I mentioned above, another is that we would be requiring all
>> >> guests running on the machine (secure guests or not, since we would use
>> >> the same configuration for all guests) to support it. But
>> >> ACCESS_PLATFORM is relatively recent so it's a bit early for that. For
>> >> instance, Ubuntu 16.04 LTS (which is still supported) doesn't know about
>> >> it and wouldn't be able to use the device.
>> >
>> > OK and your target is to enable use with kernel drivers within
>> > guests, right?
>>
>> Right.
>>
>> > My question is, we are defining a new flag here, I guess old guests
>> > then do not set it. How does it help old guests? Or maybe it's
>> > not designed to ...
>>
>> Indeed. The idea is that QEMU can offer the flag, old guests can reject
>> it (or even new guests can reject it, if they decide not to convert into
>> secure VMs) and the feature negotiation will succeed with the flag
>> unset.
>
> OK. And then what does QEMU do? Assume guest is not encrypted I guess?
There's nothing different that QEMU needs to do, with or without the
flag. the perspective of the host, a secure guest and a regular guest
work the same way with respect to virtio.
--
Thiago Jung Bauermann
IBM Linux Technology Center
next prev parent reply other threads:[~2019-07-15 22:06 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <87zhrj8kcp.fsf@morokweng.localdomain>
2019-01-29 17:42 ` [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted Thiago Jung Bauermann
2019-01-29 19:02 ` Michael S. Tsirkin
2019-01-30 2:24 ` Jason Wang
2019-01-30 2:36 ` Michael S. Tsirkin
2019-01-30 3:05 ` Jason Wang
2019-01-30 3:26 ` Michael S. Tsirkin
2019-01-30 7:44 ` Christoph Hellwig
2019-02-04 18:15 ` Thiago Jung Bauermann
2019-02-04 21:38 ` Michael S. Tsirkin
2019-02-05 7:24 ` Christoph Hellwig
2019-02-05 16:13 ` Michael S. Tsirkin
2019-03-26 16:53 ` Michael S. Tsirkin
2019-02-04 18:14 ` Thiago Jung Bauermann
2019-02-04 20:23 ` Michael S. Tsirkin
2019-03-20 16:13 ` Thiago Jung Bauermann
2019-03-20 21:17 ` Michael S. Tsirkin
2019-03-22 0:05 ` Thiago Jung Bauermann
2019-03-23 21:01 ` Michael S. Tsirkin
2019-03-25 0:57 ` David Gibson
2019-04-17 21:42 ` Thiago Jung Bauermann
2019-04-17 21:42 ` Thiago Jung Bauermann
2019-04-19 23:09 ` Michael S. Tsirkin
2019-04-25 1:01 ` Thiago Jung Bauermann
2019-04-25 1:18 ` Michael S. Tsirkin
2019-04-26 23:56 ` Thiago Jung Bauermann
2019-05-20 13:08 ` Michael S. Tsirkin
2019-05-20 13:16 ` Michael S. Tsirkin
2019-06-04 1:13 ` Thiago Jung Bauermann
2019-06-04 1:42 ` Michael S. Tsirkin
2019-06-28 1:58 ` Thiago Jung Bauermann
2019-07-01 14:17 ` Michael S. Tsirkin
2019-07-14 5:51 ` Thiago Jung Bauermann
2019-07-15 14:35 ` Michael S. Tsirkin
2019-07-15 20:29 ` Thiago Jung Bauermann
2019-07-15 20:36 ` Michael S. Tsirkin
2019-07-15 22:03 ` Thiago Jung Bauermann [this message]
2019-07-15 22:16 ` Michael S. Tsirkin
2019-07-15 23:05 ` Thiago Jung Bauermann
2019-07-15 23:24 ` Benjamin Herrenschmidt
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