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From: David Gibson <david@gibson.dropbear.id.au>
To: brijesh.singh@amd.com, pair@us.ibm.com, dgilbert@redhat.com,
	pasic@linux.ibm.com, qemu-devel@nongnu.org
Cc: cohuck@redhat.com,
	Richard Henderson <richard.henderson@linaro.org>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	David Hildenbrand <david@redhat.com>,
	borntraeger@de.ibm.com,
	Marcel Apfelbaum <marcel.apfelbaum@gmail.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	mst@redhat.com, jun.nakajima@intel.com, thuth@redhat.com,
	pragyansri.pathi@intel.com, kvm@vger.kernel.org,
	Eduardo Habkost <ehabkost@redhat.com>,
	qemu-s390x@nongnu.org, qemu-ppc@nongnu.org,
	frankja@linux.ibm.com, Greg Kurz <groug@kaod.org>,
	mdroth@linux.vnet.ibm.com,
	David Gibson <david@gibson.dropbear.id.au>,
	berrange@redhat.com, andi.kleen@intel.com
Subject: [PATCH v7 12/13] confidential guest support: Alter virtio default properties for protected guests
Date: Thu, 14 Jan 2021 10:58:10 +1100	[thread overview]
Message-ID: <20210113235811.1909610-13-david@gibson.dropbear.id.au> (raw)
In-Reply-To: <20210113235811.1909610-1-david@gibson.dropbear.id.au>

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 confidential guest 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>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
---
 hw/core/machine.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 5a7433332b..61ae363559 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -33,6 +33,8 @@
 #include "migration/global_state.h"
 #include "migration/vmstate.h"
 #include "exec/confidential-guest-support.h"
+#include "hw/virtio/virtio.h"
+#include "hw/virtio/virtio-pci.h"
 
 GlobalProperty hw_compat_5_2[] = {};
 const size_t hw_compat_5_2_len = G_N_ELEMENTS(hw_compat_5_2);
@@ -1204,6 +1206,17 @@ 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 also disabling legacy virtio
+         * support for those virtio pci devices which allow it.
+         */
+        object_register_sugar_prop(TYPE_VIRTIO_PCI, "disable-legacy",
+                                   "on", true);
+        object_register_sugar_prop(TYPE_VIRTIO_DEVICE, "iommu_platform",
+                                   "on", false);
     }
 
     machine_class->init(machine);
-- 
2.29.2


  parent reply	other threads:[~2021-01-14  1:53 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-13 23:57 [PATCH v7 00/13] Generalize memory encryption models David Gibson
2021-01-13 23:57 ` [PATCH v7 01/13] qom: Allow optional sugar props David Gibson
2021-01-13 23:58 ` [PATCH v7 02/13] confidential guest support: Introduce new confidential guest support class David Gibson
2021-01-14  9:34   ` Daniel P. Berrangé
2021-01-14 10:42     ` David Gibson
2021-01-18 18:51   ` Dr. David Alan Gilbert
2021-01-21  1:06     ` David Gibson
2021-01-21  9:08       ` Dr. David Alan Gilbert
2021-01-29  2:32         ` David Gibson
2021-01-13 23:58 ` [PATCH v7 03/13] sev: Remove false abstraction of flash encryption David Gibson
2021-01-15 12:54   ` Cornelia Huck
2021-01-18  2:59     ` David Gibson
2021-01-13 23:58 ` [PATCH v7 04/13] confidential guest support: Move side effect out of machine_set_memory_encryption() David Gibson
2021-01-15 12:56   ` Cornelia Huck
2021-01-13 23:58 ` [PATCH v7 05/13] confidential guest support: Rework the "memory-encryption" property David Gibson
2021-01-15 13:06   ` Cornelia Huck
2021-01-13 23:58 ` [PATCH v7 06/13] sev: Add Error ** to sev_kvm_init() David Gibson
2021-01-13 23:58 ` [PATCH v7 07/13] confidential guest support: Introduce cgs "ready" flag David Gibson
2021-01-14  8:55   ` Greg Kurz
2021-01-15 13:12   ` Cornelia Huck
2021-01-18 19:47   ` Dr. David Alan Gilbert
2021-01-19  8:16     ` Cornelia Huck
2021-02-02  1:41       ` David Gibson
2021-01-13 23:58 ` [PATCH v7 08/13] confidential guest support: Move SEV initialization into arch specific code David Gibson
2021-01-15 13:24   ` Cornelia Huck
2021-01-18  3:03     ` David Gibson
2021-01-18  8:03       ` Cornelia Huck
2021-01-29  3:12         ` David Gibson
2021-01-13 23:58 ` [PATCH v7 09/13] confidential guest support: Update documentation David Gibson
2021-01-14 10:07   ` Greg Kurz
2021-01-15 15:36   ` Cornelia Huck
2021-01-29  2:36     ` David Gibson
2021-01-13 23:58 ` [PATCH v7 10/13] spapr: Add PEF based confidential guest support David Gibson
2021-01-15 15:41   ` Cornelia Huck
2021-01-29  2:43     ` David Gibson
2021-01-13 23:58 ` [PATCH v7 11/13] spapr: PEF: prevent migration David Gibson
2021-01-13 23:58 ` David Gibson [this message]
2021-01-13 23:58 ` [PATCH v7 13/13] s390: Recognize confidential-guest-support option David Gibson
2021-01-14  9:10   ` Christian Borntraeger
2021-01-14  9:19     ` Christian Borntraeger
2021-01-14  9:24       ` Christian Borntraeger
2021-01-15  0:13         ` David Gibson
2021-01-14 11:45     ` David Gibson
2021-01-15 16:36   ` Cornelia Huck
2021-01-18 17:06     ` Christian Borntraeger

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