From: "Daniel P. Berrangé" <berrange@redhat.com>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: qemu-devel@nongnu.org, brijesh.singh@amd.com, pair@us.ibm.com,
pbonzini@redhat.com, dgilbert@redhat.com, frankja@linux.ibm.com,
Eduardo Habkost <ehabkost@redhat.com>,
kvm@vger.kernel.org, mst@redhat.com, cohuck@redhat.com,
david@redhat.com, mdroth@linux.vnet.ibm.com, pasic@linux.ibm.com,
qemu-s390x@nongnu.org, qemu-ppc@nongnu.org,
Richard Henderson <rth@twiddle.net>
Subject: Re: [PATCH v3 9/9] host trust limitation: Alter virtio default properties for protected guests
Date: Fri, 19 Jun 2020 16:05:56 +0100 [thread overview]
Message-ID: <20200619150556.GW700896@redhat.com> (raw)
In-Reply-To: <20200619144541.GM17085@umbus.fritz.box>
On Sat, Jun 20, 2020 at 12:45:41AM +1000, David Gibson wrote:
> On Fri, Jun 19, 2020 at 11:12:45AM +0100, Daniel P. Berrangé wrote:
> > On Fri, Jun 19, 2020 at 12:06:02PM +1000, David Gibson wrote:
> > > The default behaviour for virtio devices is not to use the platforms normal
> > > DMA paths, but instead to use the fact that it's running in a hypervisor
> > > to directly access guest memory. That doesn't work if the guest's memory
> > > is protected from hypervisor access, such as with AMD's SEV or POWER's PEF.
> > >
> > > So, if a host trust limitation mechanism is enabled, then apply the
> > > iommu_platform=on option so it will go through normal DMA mechanisms.
> > > Those will presumably have some way of marking memory as shared with the
> > > hypervisor or hardware so that DMA will work.
> > >
> > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > > ---
> > > hw/core/machine.c | 11 +++++++++++
> > > 1 file changed, 11 insertions(+)
> > >
> > > diff --git a/hw/core/machine.c b/hw/core/machine.c
> > > index a71792bc16..8dfc1bb3f8 100644
> > > --- a/hw/core/machine.c
> > > +++ b/hw/core/machine.c
> > > @@ -28,6 +28,8 @@
> > > #include "hw/mem/nvdimm.h"
> > > #include "migration/vmstate.h"
> > > #include "exec/host-trust-limitation.h"
> > > +#include "hw/virtio/virtio.h"
> > > +#include "hw/virtio/virtio-pci.h"
> > >
> > > GlobalProperty hw_compat_5_0[] = {
> > > { "virtio-balloon-device", "page-poison", "false" },
> > > @@ -1165,6 +1167,15 @@ void machine_run_board_init(MachineState *machine)
> > > * areas.
> > > */
> > > machine_set_mem_merge(OBJECT(machine), false, &error_abort);
> > > +
> > > + /*
> > > + * Virtio devices can't count on directly accessing guest
> > > + * memory, so they need iommu_platform=on to use normal DMA
> > > + * mechanisms. That requires disabling legacy virtio support
> > > + * for virtio pci devices
> > > + */
> > > + object_register_sugar_prop(TYPE_VIRTIO_PCI, "disable-legacy", "on");
> > > + object_register_sugar_prop(TYPE_VIRTIO_DEVICE, "iommu_platform", "on");
> > > }
> >
> > Silently changing the user's request configuration like this
>
> It doesn't, though. register_sugar_prop() effectively registers a
> default, so if the user has explicitly specified something, that will
> take precedence.
Don't assume that the user has set "disable-legacy=off". People who want to
have a transtional device are almost certainly pasing "-device virtio-blk-pci",
because historical behaviour is that this is sufficient to give you a
transitional device. Changing the default of disable-legacy=on has not
honoured the users' requested config.
Regards,
Daniel
--
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next prev parent reply other threads:[~2020-06-19 16:10 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-19 2:05 [PATCH v3 0/9] Generalize memory encryption models David Gibson
2020-06-19 2:05 ` [PATCH v3 1/9] host trust limitation: Introduce new host trust limitation interface David Gibson
2020-06-26 11:01 ` Dr. David Alan Gilbert
2020-07-14 19:26 ` Richard Henderson
2020-06-19 2:05 ` [PATCH v3 2/9] host trust limitation: Handle memory encryption via interface David Gibson
2020-06-19 2:05 ` [PATCH v3 3/9] host trust limitation: Move side effect out of machine_set_memory_encryption() David Gibson
2020-06-19 2:05 ` [PATCH v3 4/9] host trust limitation: Rework the "memory-encryption" property David Gibson
2020-07-14 19:36 ` Richard Henderson
2020-06-19 2:05 ` [PATCH v3 5/9] host trust limitation: Decouple kvm_memcrypt_*() helpers from KVM David Gibson
2020-06-19 2:05 ` [PATCH v3 6/9] host trust limitation: Add Error ** to HostTrustLimitation::kvm_init David Gibson
2020-06-19 2:06 ` [PATCH v3 7/9] spapr: Add PEF based host trust limitation David Gibson
2020-06-19 2:06 ` [PATCH v3 8/9] spapr: PEF: block migration David Gibson
2020-06-26 10:33 ` Dr. David Alan Gilbert
2020-07-05 7:38 ` David Gibson
2020-06-19 2:06 ` [PATCH v3 9/9] host trust limitation: Alter virtio default properties for protected guests David Gibson
2020-06-19 10:12 ` Daniel P. Berrangé
2020-06-19 11:46 ` Michael S. Tsirkin
2020-06-19 11:47 ` Michael S. Tsirkin
2020-06-19 12:16 ` Daniel P. Berrangé
2020-06-19 20:04 ` Halil Pasic
2020-06-24 7:55 ` Michael S. Tsirkin
2020-06-25 4:57 ` David Gibson
2020-06-25 5:02 ` David Gibson
2020-06-19 14:45 ` David Gibson
2020-06-19 15:05 ` Daniel P. Berrangé [this message]
2020-06-20 8:24 ` David Gibson
2020-06-22 9:09 ` Daniel P. Berrangé
2020-06-25 5:06 ` David Gibson
2020-06-19 2:42 ` [PATCH v3 0/9] Generalize memory encryption models no-reply
2020-06-19 8:28 ` David Hildenbrand
2020-06-19 9:45 ` Cornelia Huck
2020-06-19 9:56 ` David Hildenbrand
2020-06-19 10:05 ` Cornelia Huck
2020-06-19 10:10 ` David Hildenbrand
2020-06-22 12:02 ` Cornelia Huck
2020-06-25 5:25 ` David Gibson
2020-06-25 7:06 ` David Hildenbrand
2020-06-26 4:42 ` David Gibson
2020-06-26 6:53 ` David Hildenbrand
2020-06-26 9:01 ` Janosch Frank
2020-06-26 9:32 ` Daniel P. Berrangé
2020-06-26 9:49 ` Janosch Frank
2020-06-26 10:29 ` Dr. David Alan Gilbert
2020-06-26 10:58 ` Daniel P. Berrangé
2020-06-26 12:49 ` Janosch Frank
2020-07-01 11:59 ` Halil Pasic
2020-06-19 9:48 ` David Gibson
2020-06-19 10:04 ` David Hildenbrand
2020-06-25 5:42 ` David Gibson
2020-06-25 6:59 ` David Hildenbrand
2020-06-25 9:49 ` Cornelia Huck
2020-06-22 14:27 ` Christian Borntraeger
2020-06-24 7:06 ` Cornelia Huck
2020-06-25 5:47 ` David Gibson
2020-06-25 5:48 ` David Gibson
2020-06-25 5:44 ` David Gibson
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