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116 lines
4.8 KiB
116 lines
4.8 KiB
9 months ago
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From c731ffdf9faee74e9522dff06e61cda817902088 Mon Sep 17 00:00:00 2001
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From: Halil Pasic <pasic@linux.ibm.com>
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Date: Mon, 7 Feb 2022 12:28:57 +0100
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Subject: [PATCH 1/2] virtio: fix the condition for iommu_platform not
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supported
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
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RH-MergeRequest: 224: virtiofs on s390 secure execution
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RH-Bugzilla: 2116302
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
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RH-Acked-by: Cédric Le Goater <None>
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RH-Commit: [1/2] d7edc7e3905a04644c9ff44b0d36122c72068e08
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The commit 04ceb61a40 ("virtio: Fail if iommu_platform is requested, but
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unsupported") claims to fail the device hotplug when iommu_platform
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is requested, but not supported by the (vhost) device. On the first
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glance the condition for detecting that situation looks perfect, but
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because a certain peculiarity of virtio_platform it ain't.
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In fact the aforementioned commit introduces a regression. It breaks
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virtio-fs support for Secure Execution, and most likely also for AMD SEV
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or any other confidential guest scenario that relies encrypted guest
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memory. The same also applies to any other vhost device that does not
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support _F_ACCESS_PLATFORM.
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The peculiarity is that iommu_platform and _F_ACCESS_PLATFORM collates
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"device can not access all of the guest RAM" and "iova != gpa, thus
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device needs to translate iova".
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Confidential guest technologies currently rely on the device/hypervisor
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offering _F_ACCESS_PLATFORM, so that, after the feature has been
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negotiated, the guest grants access to the portions of memory the
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device needs to see. So in for confidential guests, generally,
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_F_ACCESS_PLATFORM is about the restricted access to memory, but not
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about the addresses used being something else than guest physical
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addresses.
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This is the very reason for which commit f7ef7e6e3b ("vhost: correctly
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turn on VIRTIO_F_IOMMU_PLATFORM") fences _F_ACCESS_PLATFORM from the
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vhost device that does not need it, because on the vhost interface it
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only means "I/O address translation is needed".
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This patch takes inspiration from f7ef7e6e3b ("vhost: correctly turn on
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VIRTIO_F_IOMMU_PLATFORM"), and uses the same condition for detecting the
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situation when _F_ACCESS_PLATFORM is requested, but no I/O translation
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by the device, and thus no device capability is needed. In this
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situation claiming that the device does not support iommu_plattform=on
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is counter-productive. So let us stop doing that!
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Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
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Reported-by: Jakob Naucke <Jakob.Naucke@ibm.com>
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Fixes: 04ceb61a40 ("virtio: Fail if iommu_platform is requested, but
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unsupported")
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Acked-by: Cornelia Huck <cohuck@redhat.com>
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Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
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Tested-by: Daniel Henrique Barboza <danielhb413@gmail.com>
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Cc: Kevin Wolf <kwolf@redhat.com>
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Cc: qemu-stable@nongnu.org
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Message-Id: <20220207112857.607829-1-pasic@linux.ibm.com>
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Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Acked-by: Jason Wang <jasowang@redhat.com>
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(cherry picked from commit e65902a913bf31ba79a83a3bd3621108b85cf645)
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---
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hw/virtio/virtio-bus.c | 12 +++++++-----
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1 file changed, 7 insertions(+), 5 deletions(-)
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diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
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index d23db98c56..0f69d1c742 100644
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--- a/hw/virtio/virtio-bus.c
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+++ b/hw/virtio/virtio-bus.c
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@@ -48,6 +48,7 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp)
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VirtioBusClass *klass = VIRTIO_BUS_GET_CLASS(bus);
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VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
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bool has_iommu = virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM);
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+ bool vdev_has_iommu;
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Error *local_err = NULL;
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DPRINTF("%s: plug device.\n", qbus->name);
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@@ -69,11 +70,6 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp)
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return;
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}
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- if (has_iommu && !virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) {
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- error_setg(errp, "iommu_platform=true is not supported by the device");
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- return;
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- }
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-
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if (klass->device_plugged != NULL) {
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klass->device_plugged(qbus->parent, &local_err);
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}
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@@ -82,9 +78,15 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp)
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return;
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}
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+ vdev_has_iommu = virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM);
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if (klass->get_dma_as != NULL && has_iommu) {
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virtio_add_feature(&vdev->host_features, VIRTIO_F_IOMMU_PLATFORM);
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vdev->dma_as = klass->get_dma_as(qbus->parent);
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+ if (!vdev_has_iommu && vdev->dma_as != &address_space_memory) {
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+ error_setg(errp,
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+ "iommu_platform=true is not supported by the device");
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+ return;
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+ }
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} else {
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vdev->dma_as = &address_space_memory;
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}
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--
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2.37.3
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