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RE: [PATCH 1/3] virtio-iommu: Add bypass mode support to assigned device
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From: |
Duan, Zhenzhong |
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Subject: |
RE: [PATCH 1/3] virtio-iommu: Add bypass mode support to assigned device |
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Date: |
Fri, 24 Jun 2022 08:28:51 +0000 |
>-----Original Message-----
>From: Eric Auger <eric.auger@redhat.com>
>Sent: Friday, June 24, 2022 12:52 AM
>To: Duan, Zhenzhong <zhenzhong.duan@intel.com>
>Cc: qemu-devel@nongnu.org; mst@redhat.com; jean-philippe@linaro.org;
>pbonzini@redhat.com; Zhang, Yu C <yu.c.zhang@intel.com>; Dong,
>Chuanxiao <chuanxiao.dong@intel.com>; Zhang, Tina
><tina.zhang@intel.com>
>Subject: Re: [PATCH 1/3] virtio-iommu: Add bypass mode support to
>assigned device
>
>Hi,
>On 6/13/22 08:10, Zhenzhong Duan wrote:
>> Currently assigned devices can not work in virtio-iommu bypass mode.
>> Guest driver fails to probe the device due to DMA failure. And the
>> reason is because of lacking GPA -> HPA mappings when VM is created.
>>
>> Add a root container memory region to hold both bypass memory region
>> and iommu memory region, so the switch between them is supported just
>> like the implementation in virtual VT-d.
>>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>> ---
>> hw/virtio/trace-events | 1 +
>> hw/virtio/virtio-iommu.c | 115 ++++++++++++++++++++++++++++++-
>> include/hw/virtio/virtio-iommu.h | 2 +
>> 3 files changed, 116 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events index
>> ab8e095b73fa..20af2e7ebd78 100644
>> --- a/hw/virtio/trace-events
>> +++ b/hw/virtio/trace-events
>> @@ -124,6 +124,7 @@ virtio_iommu_remap(const char *name, uint64_t
>> virt_start, uint64_t virt_end, uin
>> virtio_iommu_set_page_size_mask(const char *name, uint64_t old,
>uint64_t new) "mr=%s old_mask=0x%"PRIx64" new_mask=0x%"PRIx64
>virtio_iommu_notify_flag_add(const char *name) "add notifier to mr %s"
>> virtio_iommu_notify_flag_del(const char *name) "del notifier from mr %s"
>> +virtio_iommu_switch_address_space(uint8_t bus, uint8_t slot, uint8_t fn,
>bool on) "Device %02x:%02x.%x switching address space (iommu
>enabled=%d)"
>>
>> # virtio-mem.c
>> virtio_mem_send_response(uint16_t type) "type=%" PRIu16 diff --git
>> a/hw/virtio/virtio-iommu.c b/hw/virtio/virtio-iommu.c index
>> 2597e166f939..ff718107ee02 100644
>> --- a/hw/virtio/virtio-iommu.c
>> +++ b/hw/virtio/virtio-iommu.c
>> @@ -69,6 +69,77 @@ static inline uint16_t
>virtio_iommu_get_bdf(IOMMUDevice *dev)
>> return PCI_BUILD_BDF(pci_bus_num(dev->bus), dev->devfn); }
>>
>> +static bool virtio_iommu_device_bypassed(IOMMUDevice *sdev) {
>> + uint32_t sid;
>> + bool bypassed;
>> + VirtIOIOMMU *s = sdev->viommu;
>> + VirtIOIOMMUEndpoint *ep;
>> +
>> + sid = virtio_iommu_get_bdf(sdev);
>> +
>> + qemu_mutex_lock(&s->mutex);
>> + /* need to check bypass before system reset */
>> + if (!s->endpoints) {
>> + bypassed = s->config.bypass;
>> + goto unlock;
>> + }
>> +
>> + ep = g_tree_lookup(s->endpoints, GUINT_TO_POINTER(sid));
>> + if (!ep || !ep->domain) {
>> + bypassed = s->config.bypass;
>> + } else {
>> + bypassed = ep->domain->bypass;
>> + }
>> +
>> +unlock:
>> + qemu_mutex_unlock(&s->mutex);
>> + return bypassed;
>> +}
>> +
>> +/* Return whether the device is using IOMMU translation. */ static
>> +bool virtio_iommu_switch_address_space(IOMMUDevice *sdev) {
>> + bool use_remapping;
>> +
>> + assert(sdev);
>> +
>> + use_remapping = !virtio_iommu_device_bypassed(sdev);
>> +
>> + trace_virtio_iommu_switch_address_space(pci_bus_num(sdev->bus),
>> + PCI_SLOT(sdev->devfn),
>> + PCI_FUNC(sdev->devfn),
>> + use_remapping);
>> +
>> + /* Turn off first then on the other */
>> + if (use_remapping) {
>> + memory_region_set_enabled(&sdev->bypass_mr, false);
>> + memory_region_set_enabled(MEMORY_REGION(&sdev->iommu_mr),
>true);
>> + } else {
>> + memory_region_set_enabled(MEMORY_REGION(&sdev->iommu_mr),
>false);
>> + memory_region_set_enabled(&sdev->bypass_mr, true);
>> + }
>> +
>> + return use_remapping;
>> +}
>> +
>> +static void virtio_iommu_switch_address_space_all(VirtIOIOMMU *s) {
>> + GHashTableIter iter;
>> + IOMMUPciBus *iommu_pci_bus;
>> + int i;
>> +
>> + g_hash_table_iter_init(&iter, s->as_by_busptr);
>> + while (g_hash_table_iter_next(&iter, NULL, (void **)&iommu_pci_bus))
>{
>> + for (i = 0; i < PCI_DEVFN_MAX; i++) {
>> + if (!iommu_pci_bus->pbdev[i]) {
>> + continue;
>> + }
>> + virtio_iommu_switch_address_space(iommu_pci_bus->pbdev[i]);
>> + }
>> + }
>> +}
>> +
>> /**
>> * The bus number is used for lookup when SID based operations occur.
>> * In that case we lazily populate the IOMMUPciBus array from the bus
>> hash @@ -213,6 +284,7 @@ static gboolean
>> virtio_iommu_notify_map_cb(gpointer key, gpointer value, static void
>> virtio_iommu_detach_endpoint_from_domain(VirtIOIOMMUEndpoint *ep)
>{
>> VirtIOIOMMUDomain *domain = ep->domain;
>> + IOMMUDevice *sdev = container_of(ep->iommu_mr, IOMMUDevice,
>> + iommu_mr);
>>
>> if (!ep->domain) {
>> return;
>> @@ -221,6 +293,7 @@ static void
>virtio_iommu_detach_endpoint_from_domain(VirtIOIOMMUEndpoint *ep)
>> ep->iommu_mr);
>> QLIST_REMOVE(ep, next);
>> ep->domain = NULL;
>> + virtio_iommu_switch_address_space(sdev);
>> }
>>
>> static VirtIOIOMMUEndpoint *virtio_iommu_get_endpoint(VirtIOIOMMU
>*s,
>> @@ -323,12 +396,39 @@ static AddressSpace
>> *virtio_iommu_find_add_as(PCIBus *bus, void *opaque,
>>
>> trace_virtio_iommu_init_iommu_mr(name);
>>
>> + memory_region_init(&sdev->root, OBJECT(s), name, UINT64_MAX);
>> + address_space_init(&sdev->as, &sdev->root,
>> + TYPE_VIRTIO_IOMMU);
>> +
>> + /*
>> + * Build the IOMMU disabled container with aliases to the
>> + * shared MRs. Note that aliasing to a shared memory region
>What do you call the 'disabled container' and the shared MRs?
' IOMMU disabled container' means sdev->bypass_mr.
Shared MRs means get_system_memory(), aka system_memory.
All endpoint's sdev->bypass_mr alias to system_memory, so saying
sdev->bypass_mr 'IOMMU disabled' and system_memory shared MRs.
>
>> + * could help the memory API to detect same FlatViews so we
>> + * can have devices to share the same FlatView when in bypass
>> + * mode. (either by not configuring virtio-iommu driver or with
>> + * "iommu=pt"). It will greatly reduce the total number of
>> + * FlatViews of the system hence VM runs faster.
>
>Do you mean that we could have used a shared bypass MR instead of
>creatingone per device?
I think we still need to create iommu MR per device which is enabled when
endpoint attached to dma domain.
Shared bypass MR is enabled when:
1. endpoint not attached to any domain yet and virtio-iommu.boot_bypass=true
2. endpoint is attached to bypass domain
>> + */
>> + memory_region_init_alias(&sdev->bypass_mr, OBJECT(s),
>> + "system", get_system_memory(), 0,
>> +
>> + memory_region_size(get_system_memory()));
>> +
>> memory_region_init_iommu(&sdev->iommu_mr, sizeof(sdev-
>>iommu_mr),
>> TYPE_VIRTIO_IOMMU_MEMORY_REGION,
>> OBJECT(s), name,
>> UINT64_MAX);
>> - address_space_init(&sdev->as,
>> - MEMORY_REGION(&sdev->iommu_mr),
>TYPE_VIRTIO_IOMMU);
>> +
>> + /*
>> + * Hook both the containers under the root container, we
>did you mean "hook both sub-regions to the root container"?
Yes
>> + * switch between iommu & bypass MRs by enable/disable
>> + * corresponding sub-containers
>> + */
>> + memory_region_add_subregion_overlap(&sdev->root, 0,
>> + MEMORY_REGION(&sdev->iommu_mr),
>> + 0);
>> + memory_region_add_subregion_overlap(&sdev->root, 0,
>> + &sdev->bypass_mr, 0);
>> +
>> + virtio_iommu_switch_address_space(sdev);
>> g_free(name);
>> }
>> return &sdev->as;
>> @@ -342,6 +442,7 @@ static int virtio_iommu_attach(VirtIOIOMMU *s,
>> uint32_t flags = le32_to_cpu(req->flags);
>> VirtIOIOMMUDomain *domain;
>> VirtIOIOMMUEndpoint *ep;
>> + IOMMUDevice *sdev;
>>
>> trace_virtio_iommu_attach(domain_id, ep_id);
>>
>> @@ -375,6 +476,8 @@ static int virtio_iommu_attach(VirtIOIOMMU *s,
>> QLIST_INSERT_HEAD(&domain->endpoint_list, ep, next);
>>
>> ep->domain = domain;
>> + sdev = container_of(ep->iommu_mr, IOMMUDevice, iommu_mr);
>> + virtio_iommu_switch_address_space(sdev);
>>
>> /* Replay domain mappings on the associated memory region */
>> g_tree_foreach(domain->mappings, virtio_iommu_notify_map_cb, @@
>> -887,6 +990,7 @@ static void virtio_iommu_set_config(VirtIODevice *vdev,
>> return;
>> }
>> dev_config->bypass = in_config->bypass;
>> + virtio_iommu_switch_address_space_all(dev);
>> }
>>
>> trace_virtio_iommu_set_config(in_config->bypass);
>> @@ -1026,6 +1130,8 @@ static void virtio_iommu_system_reset(void
>*opaque)
>> * system reset
>> */
>> s->config.bypass = s->boot_bypass;
>> + virtio_iommu_switch_address_space_all(s);
>> +
>> }
>>
>> static void virtio_iommu_device_realize(DeviceState *dev, Error
>> **errp) @@ -1041,6 +1147,11 @@ static void
>virtio_iommu_device_realize(DeviceState *dev, Error **errp)
>> virtio_iommu_handle_command);
>> s->event_vq = virtio_add_queue(vdev, VIOMMU_DEFAULT_QUEUE_SIZE,
>> NULL);
>>
>> + /*
>> + * config.bypass is needed to get initial address space early, such as
>> + * in vfio realize
>> + */
>I don't understand this comment, please can you elaborate?
In vfio_realize(), virtio_iommu_find_add_as() is called to get the address space
from virtio-iommu. virtio_iommu_find_add_as() calls
virtio_iommu_switch_address_space()
and virtio_iommu_switch_address_space() need to check config.bypass to enable
the right MRs, either shared bypass MR or iommu MR.
It could be ok to use s->boot_bypass directly in virtio_iommu_device_bypassed(),
then this change could be removed.
>> + s->config.bypass = s->boot_bypass;
>> s->config.page_size_mask = TARGET_PAGE_MASK;
>> s->config.input_range.end = UINT64_MAX;
>> s->config.domain_range.end = UINT32_MAX; diff --git
>> a/include/hw/virtio/virtio-iommu.h b/include/hw/virtio/virtio-iommu.h
>> index 84391f844826..102eeefa731d 100644
>> --- a/include/hw/virtio/virtio-iommu.h
>> +++ b/include/hw/virtio/virtio-iommu.h
>> @@ -37,6 +37,8 @@ typedef struct IOMMUDevice {
>> int devfn;
>> IOMMUMemoryRegion iommu_mr;
>> AddressSpace as;
>> + MemoryRegion root; /* The root container of the device */
>> + MemoryRegion bypass_mr; /* The alias of shared memory MR */
>> } IOMMUDevice;
>>
>> typedef struct IOMMUPciBus {
>Did you test migration? I wonder if we shouldn't call
>
>virtio_iommu_switch_address_space_all(s)
>after restoring the endpoints in iommu_post_load() as it is done in intel-
>iommu
Thanks for point out, I missed the migration scenario. After your suggested
change, the migration works without pass-through device. With pass-through
device I got "VFIO device doesn't support migration". Not clear if
pass-through device migration is totally supported now.
Zhenzhong