From: David Gibson <david@gibson.dropbear.id.au>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Mike Anderson <andmike@linux.ibm.com>,
Jean-Philippe Brucker <jean-philippe.brucker@arm.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Alexey Kardashevskiy <aik@linux.ibm.com>,
Ram Pai <linuxram@us.ibm.com>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
Paul Mackerras <paulus@ozlabs.org>,
iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org,
Christoph Hellwig <hch@lst.de>
Subject: Re: [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted
Date: Mon, 25 Mar 2019 11:57:10 +1100 [thread overview]
Message-ID: <20190325005710.GC29295@umbus> (raw)
In-Reply-To: <20190323165456-mutt-send-email-mst@kernel.org>
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On Sat, Mar 23, 2019 at 05:01:35PM -0400, Michael S. Tsirkin wrote:
> On Thu, Mar 21, 2019 at 09:05:04PM -0300, Thiago Jung Bauermann wrote:
> > Michael S. Tsirkin <mst@redhat.com> writes:
[snip]
> > >> > Is there any justification to doing that beyond someone putting
> > >> > out slow code in the past?
> > >>
> > >> The definition of the ACCESS_PLATFORM flag is generic and captures the
> > >> notion of memory access restrictions for the device. Unfortunately, on
> > >> powerpc pSeries guests it also implies that the IOMMU is turned on
> > >
> > > IIUC that's really because on pSeries IOMMU is *always* turned on.
> > > Platform has no way to say what you want it to say
> > > which is bypass the iommu for the specific device.
> >
> > Yes, that's correct. pSeries guests running on KVM are in a gray area
> > where theoretically they use an IOMMU but in practice KVM ignores it.
> > It's unfortunate but it's the reality on the ground today. :-/
Um.. I'm not sure what you mean by this. As far as I'm concerned
there is always a guest-visible (paravirtualized) IOMMU, and that will
be backed onto the host IOMMU when necessary.
[Actually there is an IOMMU bypass hack that's used by the guest
firmware, but I don't think we want to expose that]
> Well it's not just the reality, virt setups need something that
> emulated IOMMUs don't provide. That is not uncommon, e.g.
> intel's VTD has a "cache mode" field which AFAIK is only used for virt.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2019-03-25 0:57 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-29 17:08 [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted Thiago Jung Bauermann
2019-01-29 17:42 ` 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
[not found] ` <20190205072407.GA4311-jcswGhMUV9g@public.gmane.org>
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 [this message]
2019-04-17 21:42 ` Thiago Jung Bauermann
2019-04-17 21:42 ` Thiago Jung Bauermann
[not found] ` <20190323165456-mutt-send-email-mst-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2019-04-17 21:42 ` Thiago Jung Bauermann
2019-04-17 21:42 ` Thiago Jung Bauermann
2019-04-19 23:09 ` Michael S. Tsirkin
2019-04-19 23:09 ` Michael S. Tsirkin
2019-04-25 1:01 ` Thiago Jung Bauermann
2019-04-25 1:01 ` Thiago Jung Bauermann
[not found] ` <875zr228zf.fsf-wxVGo8vDogbJvNEK5ZsId7p2dZbC/Bob@public.gmane.org>
2019-04-25 1:18 ` Michael S. Tsirkin
2019-04-25 1:18 ` Michael S. Tsirkin
2019-04-26 23:56 ` Thiago Jung Bauermann
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
2019-07-15 22:16 ` Michael S. Tsirkin
2019-07-15 23:05 ` Thiago Jung Bauermann
2019-07-15 23:24 ` Benjamin Herrenschmidt
2019-07-18 3:39 ` Thiago Jung Bauermann
2019-08-10 18:57 ` Michael S. Tsirkin
2019-08-10 22:07 ` Ram Pai
2019-08-11 5:56 ` Christoph Hellwig
2019-08-11 6:46 ` Ram Pai
2019-08-11 8:44 ` Michael S. Tsirkin
2019-08-12 12:13 ` Christoph Hellwig
2019-08-12 20:29 ` Ram Pai
2019-08-11 8:42 ` Michael S. Tsirkin
2019-08-11 8:55 ` Michael S. Tsirkin
2019-08-12 12:15 ` Christoph Hellwig
2019-09-06 5:07 ` Michael S. Tsirkin
2019-08-12 9:51 ` David Gibson
2019-08-13 13:26 ` Christoph Hellwig
2019-08-13 14:24 ` David Gibson
2019-08-13 15:45 ` Ram Pai
2019-08-26 17:48 ` Ram Pai
2019-08-11 8:12 ` Michael S. Tsirkin
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