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virtio-iommu: Default to bypass during boot
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Currently the virtio-iommu device must be programmed before it allows
DMA from any PCI device. This can make the VM entirely unusable when a
virtio-iommu driver isn't present, for example in a bootloader that
loads the OS from storage.

Similarly to the other vIOMMU implementations, default to DMA bypassing
the IOMMU during boot. Add a "boot-bypass" property, defaulting to true,
that lets users change this behavior.

Replace the VIRTIO_IOMMU_F_BYPASS feature, which didn't support bypass
before feature negotiation, with VIRTIO_IOMMU_F_BYPASS_CONFIG.

We add the bypass field to the migration stream without introducing
subsections, based on the assumption that this virtio-iommu device isn't
being used in production enough to require cross-version migration at
the moment (all previous version required workarounds since they didn't
support ACPI and boot-bypass).

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Message-Id: <20220214124356.872985-3-jean-philippe@linaro.org>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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@jpbrucker @mstsirkin
jpbrucker authored and mstsirkin committed Mar 4, 2022
1 parent 0e5d0b3 commit dd19efd
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Showing 3 changed files with 56 additions and 9 deletions.
4 changes: 3 additions & 1 deletion hw/virtio/trace-events
View file
Expand Up @@ -89,9 +89,11 @@ virtio_mmio_setting_irq(int level) "virtio_mmio setting IRQ %d"

# virtio-iommu.c
virtio_iommu_device_reset(void) "reset!"
virtio_iommu_system_reset(void) "system reset!"
virtio_iommu_get_features(uint64_t features) "device supports features=0x%"PRIx64
virtio_iommu_device_status(uint8_t status) "driver status = %d"
virtio_iommu_get_config(uint64_t page_size_mask, uint64_t start, uint64_t end, uint32_t domain_start, uint32_t domain_end, uint32_t probe_size) "page_size_mask=0x%"PRIx64" input range start=0x%"PRIx64" input range end=0x%"PRIx64" domain range start=%d domain range end=%d probe_size=0x%x"
virtio_iommu_get_config(uint64_t page_size_mask, uint64_t start, uint64_t end, uint32_t domain_start, uint32_t domain_end, uint32_t probe_size, uint8_t bypass) "page_size_mask=0x%"PRIx64" input range start=0x%"PRIx64" input range end=0x%"PRIx64" domain range start=%d domain range end=%d probe_size=0x%x bypass=0x%x"
virtio_iommu_set_config(uint8_t bypass) "bypass=0x%x"
virtio_iommu_attach(uint32_t domain_id, uint32_t ep_id) "domain=%d endpoint=%d"
virtio_iommu_detach(uint32_t domain_id, uint32_t ep_id) "domain=%d endpoint=%d"
virtio_iommu_map(uint32_t domain_id, uint64_t virt_start, uint64_t virt_end, uint64_t phys_start, uint32_t flags) "domain=%d virt_start=0x%"PRIx64" virt_end=0x%"PRIx64 " phys_start=0x%"PRIx64" flags=%d"
Expand Down
60 changes: 52 additions & 8 deletions hw/virtio/virtio-iommu.c
View file
Expand Up @@ -24,6 +24,7 @@
#include "hw/qdev-properties.h"
#include "hw/virtio/virtio.h"
#include "sysemu/kvm.h"
#include "sysemu/reset.h"
#include "qapi/error.h"
#include "qemu/error-report.h"
#include "trace.h"
Expand Down Expand Up @@ -728,8 +729,7 @@ static IOMMUTLBEntry virtio_iommu_translate(IOMMUMemoryRegion *mr, hwaddr addr,
.perm = IOMMU_NONE,
};

bypass_allowed = virtio_vdev_has_feature(&s->parent_obj,
VIRTIO_IOMMU_F_BYPASS);
bypass_allowed = s->config.bypass;

sid = virtio_iommu_get_bdf(sdev);

Expand Down Expand Up @@ -831,13 +831,37 @@ static void virtio_iommu_get_config(VirtIODevice *vdev, uint8_t *config_data)
out_config->domain_range.start = cpu_to_le32(dev_config->domain_range.start);
out_config->domain_range.end = cpu_to_le32(dev_config->domain_range.end);
out_config->probe_size = cpu_to_le32(dev_config->probe_size);
out_config->bypass = dev_config->bypass;

trace_virtio_iommu_get_config(dev_config->page_size_mask,
dev_config->input_range.start,
dev_config->input_range.end,
dev_config->domain_range.start,
dev_config->domain_range.end,
dev_config->probe_size);
dev_config->probe_size,
dev_config->bypass);
}

static void virtio_iommu_set_config(VirtIODevice *vdev,
const uint8_t *config_data)
{
VirtIOIOMMU *dev = VIRTIO_IOMMU(vdev);
struct virtio_iommu_config *dev_config = &dev->config;
const struct virtio_iommu_config *in_config = (void *)config_data;

if (in_config->bypass != dev_config->bypass) {
if (!virtio_vdev_has_feature(vdev, VIRTIO_IOMMU_F_BYPASS_CONFIG)) {
virtio_error(vdev, "cannot set config.bypass");
return;
} else if (in_config->bypass != 0 && in_config->bypass != 1) {
virtio_error(vdev, "invalid config.bypass value '%u'",
in_config->bypass);
return;
}
dev_config->bypass = in_config->bypass;
}

trace_virtio_iommu_set_config(in_config->bypass);
}

static uint64_t virtio_iommu_get_features(VirtIODevice *vdev, uint64_t f,
Expand Down Expand Up @@ -963,6 +987,19 @@ static int virtio_iommu_set_page_size_mask(IOMMUMemoryRegion *mr,
return 0;
}

static void virtio_iommu_system_reset(void *opaque)
{
VirtIOIOMMU *s = opaque;

trace_virtio_iommu_system_reset();

/*
* config.bypass is sticky across device reset, but should be restored on
* system reset
*/
s->config.bypass = s->boot_bypass;
}

static void virtio_iommu_device_realize(DeviceState *dev, Error **errp)
{
VirtIODevice *vdev = VIRTIO_DEVICE(dev);
Expand All @@ -988,9 +1025,9 @@ static void virtio_iommu_device_realize(DeviceState *dev, Error **errp)
virtio_add_feature(&s->features, VIRTIO_IOMMU_F_INPUT_RANGE);
virtio_add_feature(&s->features, VIRTIO_IOMMU_F_DOMAIN_RANGE);
virtio_add_feature(&s->features, VIRTIO_IOMMU_F_MAP_UNMAP);
virtio_add_feature(&s->features, VIRTIO_IOMMU_F_BYPASS);
virtio_add_feature(&s->features, VIRTIO_IOMMU_F_MMIO);
virtio_add_feature(&s->features, VIRTIO_IOMMU_F_PROBE);
virtio_add_feature(&s->features, VIRTIO_IOMMU_F_BYPASS_CONFIG);

qemu_mutex_init(&s->mutex);

Expand All @@ -1001,13 +1038,17 @@ static void virtio_iommu_device_realize(DeviceState *dev, Error **errp)
} else {
error_setg(errp, "VIRTIO-IOMMU is not attached to any PCI bus!");
}

qemu_register_reset(virtio_iommu_system_reset, s);
}

static void virtio_iommu_device_unrealize(DeviceState *dev)
{
VirtIODevice *vdev = VIRTIO_DEVICE(dev);
VirtIOIOMMU *s = VIRTIO_IOMMU(dev);

qemu_unregister_reset(virtio_iommu_system_reset, s);

g_hash_table_destroy(s->as_by_busptr);
if (s->domains) {
g_tree_destroy(s->domains);
Expand Down Expand Up @@ -1141,21 +1182,22 @@ static int iommu_post_load(void *opaque, int version_id)

static const VMStateDescription vmstate_virtio_iommu_device = {
.name = "virtio-iommu-device",
.minimum_version_id = 1,
.version_id = 1,
.minimum_version_id = 2,
.version_id = 2,
.post_load = iommu_post_load,
.fields = (VMStateField[]) {
VMSTATE_GTREE_DIRECT_KEY_V(domains, VirtIOIOMMU, 1,
&vmstate_domain, VirtIOIOMMUDomain),
VMSTATE_UINT8_V(config.bypass, VirtIOIOMMU, 2),
VMSTATE_END_OF_LIST()
},
};

static const VMStateDescription vmstate_virtio_iommu = {
.name = "virtio-iommu",
.minimum_version_id = 1,
.minimum_version_id = 2,
.priority = MIG_PRI_IOMMU,
.version_id = 1,
.version_id = 2,
.fields = (VMStateField[]) {
VMSTATE_VIRTIO_DEVICE,
VMSTATE_END_OF_LIST()
Expand All @@ -1164,6 +1206,7 @@ static const VMStateDescription vmstate_virtio_iommu = {

static Property virtio_iommu_properties[] = {
DEFINE_PROP_LINK("primary-bus", VirtIOIOMMU, primary_bus, "PCI", PCIBus *),
DEFINE_PROP_BOOL("boot-bypass", VirtIOIOMMU, boot_bypass, true),
DEFINE_PROP_END_OF_LIST(),
};

Expand All @@ -1180,6 +1223,7 @@ static void virtio_iommu_class_init(ObjectClass *klass, void *data)
vdc->unrealize = virtio_iommu_device_unrealize;
vdc->reset = virtio_iommu_device_reset;
vdc->get_config = virtio_iommu_get_config;
vdc->set_config = virtio_iommu_set_config;
vdc->get_features = virtio_iommu_get_features;
vdc->set_status = virtio_iommu_set_status;
vdc->vmsd = &vmstate_virtio_iommu_device;
Expand Down
1 change: 1 addition & 0 deletions include/hw/virtio/virtio-iommu.h
View file
Expand Up @@ -58,6 +58,7 @@ struct VirtIOIOMMU {
GTree *domains;
QemuMutex mutex;
GTree *endpoints;
bool boot_bypass;
};

#endif

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