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    SubjectRe: [PATCH] qemu: Add virtio pmem device
    On Fri, 31 Aug 2018 19:00:19 +0530
    Pankaj Gupta <pagupta@redhat.com> wrote:

    > This patch adds virtio-pmem Qemu device.
    >
    > This device presents memory address range information to guest
    > which is backed by file backend type. It acts like persistent
    > memory device for KVM guest. Guest can perform read and
    > persistent write operations on this memory range with the help
    > of DAX capable filesystem.
    >
    > Persistent guest writes are assured with the help of virtio
    > based flushing interface. When guest userspace space performs
    > fsync on file fd on pmem device, a flush command is send to
    > Qemu over VIRTIO and host side flush/sync is done on backing
    > image file.
    >
    > Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
    > ---
    > Changes from RFC v3:
    > - Return EIO for host fsync failure instead of errno - Luiz, Stefan
    > - Change version for inclusion to Qemu 3.1 - Eric
    >
    > Changes from RFC v2:
    > - Use aio_worker() to avoid Qemu from hanging with blocking fsync
    > call - Stefan
    > - Use virtio_st*_p() for endianess - Stefan
    > - Correct indentation in qapi/misc.json - Eric
    >
    > hw/virtio/Makefile.objs | 3 +
    > hw/virtio/virtio-pci.c | 44 +++++
    > hw/virtio/virtio-pci.h | 14 ++
    > hw/virtio/virtio-pmem.c | 241 ++++++++++++++++++++++++++++
    > include/hw/pci/pci.h | 1 +
    > include/hw/virtio/virtio-pmem.h | 42 +++++
    > include/standard-headers/linux/virtio_ids.h | 1 +
    > qapi/misc.json | 26 ++-
    > 8 files changed, 371 insertions(+), 1 deletion(-)
    > create mode 100644 hw/virtio/virtio-pmem.c
    > create mode 100644 include/hw/virtio/virtio-pmem.h
    >
    > diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs
    > index 1b2799cfd8..7f914d45d0 100644
    > --- a/hw/virtio/Makefile.objs
    > +++ b/hw/virtio/Makefile.objs
    > @@ -10,6 +10,9 @@ obj-$(CONFIG_VIRTIO_CRYPTO) += virtio-crypto.o
    > obj-$(call land,$(CONFIG_VIRTIO_CRYPTO),$(CONFIG_VIRTIO_PCI)) += virtio-crypto-pci.o
    >
    > obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o
    > +ifeq ($(CONFIG_MEM_HOTPLUG),y)
    > +obj-$(CONFIG_LINUX) += virtio-pmem.o
    > +endif
    > obj-$(CONFIG_VHOST_VSOCK) += vhost-vsock.o
    > endif
    >
    > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
    > index 3a01fe90f0..93d3fc05c7 100644
    > --- a/hw/virtio/virtio-pci.c
    > +++ b/hw/virtio/virtio-pci.c
    > @@ -2521,6 +2521,49 @@ static const TypeInfo virtio_rng_pci_info = {
    > .class_init = virtio_rng_pci_class_init,
    > };
    >
    > +/* virtio-pmem-pci */
    > +
    > +static void virtio_pmem_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
    > +{
    > + VirtIOPMEMPCI *vpmem = VIRTIO_PMEM_PCI(vpci_dev);
    > + DeviceState *vdev = DEVICE(&vpmem->vdev);
    > +
    > + qdev_set_parent_bus(vdev, BUS(&vpci_dev->bus));
    > + object_property_set_bool(OBJECT(vdev), true, "realized", errp);
    > +}
    > +
    > +static void virtio_pmem_pci_class_init(ObjectClass *klass, void *data)
    > +{
    > + DeviceClass *dc = DEVICE_CLASS(klass);
    > + VirtioPCIClass *k = VIRTIO_PCI_CLASS(klass);
    > + PCIDeviceClass *pcidev_k = PCI_DEVICE_CLASS(klass);
    > + k->realize = virtio_pmem_pci_realize;
    > + set_bit(DEVICE_CATEGORY_MISC, dc->categories);
    > + pcidev_k->vendor_id = PCI_VENDOR_ID_REDHAT_QUMRANET;
    > + pcidev_k->device_id = PCI_DEVICE_ID_VIRTIO_PMEM;
    > + pcidev_k->revision = VIRTIO_PCI_ABI_VERSION;
    > + pcidev_k->class_id = PCI_CLASS_OTHERS;
    > +}
    > +
    > +static void virtio_pmem_pci_instance_init(Object *obj)
    > +{
    > + VirtIOPMEMPCI *dev = VIRTIO_PMEM_PCI(obj);
    > +
    > + virtio_instance_init_common(obj, &dev->vdev, sizeof(dev->vdev),
    > + TYPE_VIRTIO_PMEM);
    > + object_property_add_alias(obj, "memdev", OBJECT(&dev->vdev), "memdev",
    > + &error_abort);
    > +}
    > +
    > +static const TypeInfo virtio_pmem_pci_info = {
    > + .name = TYPE_VIRTIO_PMEM_PCI,
    > + .parent = TYPE_VIRTIO_PCI,
    > + .instance_size = sizeof(VirtIOPMEMPCI),
    > + .instance_init = virtio_pmem_pci_instance_init,
    > + .class_init = virtio_pmem_pci_class_init,
    > +};
    > +
    > +
    > /* virtio-input-pci */
    >
    > static Property virtio_input_pci_properties[] = {
    > @@ -2714,6 +2757,7 @@ static void virtio_pci_register_types(void)
    > type_register_static(&virtio_balloon_pci_info);
    > type_register_static(&virtio_serial_pci_info);
    > type_register_static(&virtio_net_pci_info);
    > + type_register_static(&virtio_pmem_pci_info);
    > #ifdef CONFIG_VHOST_SCSI
    > type_register_static(&vhost_scsi_pci_info);
    > #endif
    > diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
    > index 813082b0d7..fe74fcad3f 100644
    > --- a/hw/virtio/virtio-pci.h
    > +++ b/hw/virtio/virtio-pci.h
    > @@ -19,6 +19,7 @@
    > #include "hw/virtio/virtio-blk.h"
    > #include "hw/virtio/virtio-net.h"
    > #include "hw/virtio/virtio-rng.h"
    > +#include "hw/virtio/virtio-pmem.h"
    > #include "hw/virtio/virtio-serial.h"
    > #include "hw/virtio/virtio-scsi.h"
    > #include "hw/virtio/virtio-balloon.h"
    > @@ -57,6 +58,7 @@ typedef struct VirtIOInputHostPCI VirtIOInputHostPCI;
    > typedef struct VirtIOGPUPCI VirtIOGPUPCI;
    > typedef struct VHostVSockPCI VHostVSockPCI;
    > typedef struct VirtIOCryptoPCI VirtIOCryptoPCI;
    > +typedef struct VirtIOPMEMPCI VirtIOPMEMPCI;
    >
    > /* virtio-pci-bus */
    >
    > @@ -274,6 +276,18 @@ struct VirtIOBlkPCI {
    > VirtIOBlock vdev;
    > };
    >
    > +/*
    > + * virtio-pmem-pci: This extends VirtioPCIProxy.
    > + */
    > +#define TYPE_VIRTIO_PMEM_PCI "virtio-pmem-pci"
    > +#define VIRTIO_PMEM_PCI(obj) \
    > + OBJECT_CHECK(VirtIOPMEMPCI, (obj), TYPE_VIRTIO_PMEM_PCI)
    > +
    > +struct VirtIOPMEMPCI {
    > + VirtIOPCIProxy parent_obj;
    > + VirtIOPMEM vdev;
    > +};
    > +
    > /*
    > * virtio-balloon-pci: This extends VirtioPCIProxy.
    > */
    > diff --git a/hw/virtio/virtio-pmem.c b/hw/virtio/virtio-pmem.c
    > new file mode 100644
    > index 0000000000..69ae4c0a50
    > --- /dev/null
    > +++ b/hw/virtio/virtio-pmem.c
    > @@ -0,0 +1,241 @@
    > +/*
    > + * Virtio pmem device
    > + *
    > + * Copyright (C) 2018 Red Hat, Inc.
    > + * Copyright (C) 2018 Pankaj Gupta <pagupta@redhat.com>
    > + *
    > + * This work is licensed under the terms of the GNU GPL, version 2.
    > + * See the COPYING file in the top-level directory.
    > + *
    > + */
    > +
    > +#include "qemu/osdep.h"
    > +#include "qapi/error.h"
    > +#include "qemu-common.h"
    > +#include "qemu/error-report.h"
    > +#include "hw/virtio/virtio-access.h"
    > +#include "hw/virtio/virtio-pmem.h"
    > +#include "hw/mem/memory-device.h"
    > +#include "block/aio.h"
    > +#include "block/thread-pool.h"
    > +
    > +typedef struct VirtIOPMEMresp {
    > + int ret;
    > +} VirtIOPMEMResp;
    > +
    > +typedef struct VirtIODeviceRequest {
    > + VirtQueueElement elem;
    > + int fd;
    > + VirtIOPMEM *pmem;
    > + VirtIOPMEMResp resp;
    > +} VirtIODeviceRequest;
    > +
    > +static int worker_cb(void *opaque)
    > +{
    > + VirtIODeviceRequest *req = opaque;
    > + int err = 0;
    > +
    > + /* flush raw backing image */
    > + err = fsync(req->fd);
    > + if (err != 0) {
    > + err = EIO;
    > + }
    > + req->resp.ret = err;

    As I mentioned in the kernel patch, I think you should 1 for
    error and let the guest pick the error it wants to return to
    the calling thread.

    > +
    > + return 0;
    > +}
    > +
    > +static void done_cb(void *opaque, int ret)
    > +{
    > + VirtIODeviceRequest *req = opaque;
    > + int len = iov_from_buf(req->elem.in_sg, req->elem.in_num, 0,
    > + &req->resp, sizeof(VirtIOPMEMResp));
    > +
    > + /* Callbacks are serialized, so no need to use atomic ops. */
    > + virtqueue_push(req->pmem->rq_vq, &req->elem, len);
    > + virtio_notify((VirtIODevice *)req->pmem, req->pmem->rq_vq);
    > + g_free(req);
    > +}
    > +
    > +static void virtio_pmem_flush(VirtIODevice *vdev, VirtQueue *vq)
    > +{
    > + VirtIODeviceRequest *req;
    > + VirtIOPMEM *pmem = VIRTIO_PMEM(vdev);
    > + HostMemoryBackend *backend = MEMORY_BACKEND(pmem->memdev);
    > + ThreadPool *pool = aio_get_thread_pool(qemu_get_aio_context());
    > +
    > + req = virtqueue_pop(vq, sizeof(VirtIODeviceRequest));
    > + if (!req) {
    > + virtio_error(vdev, "virtio-pmem missing request data");
    > + return;
    > + }
    > +
    > + if (req->elem.out_num < 1 || req->elem.in_num < 1) {
    > + virtio_error(vdev, "virtio-pmem request not proper");
    > + g_free(req);
    > + return;
    > + }

    I think you should abort() in those errors.

    > + req->fd = memory_region_get_fd(&backend->mr);
    > + req->pmem = pmem;
    > + thread_pool_submit_aio(pool, worker_cb, req, done_cb, req);
    > +}
    > +
    > +static void virtio_pmem_get_config(VirtIODevice *vdev, uint8_t *config)
    > +{
    > + VirtIOPMEM *pmem = VIRTIO_PMEM(vdev);
    > + struct virtio_pmem_config *pmemcfg = (struct virtio_pmem_config *) config;
    > +
    > + virtio_stq_p(vdev, &pmemcfg->start, pmem->start);
    > + virtio_stq_p(vdev, &pmemcfg->size, pmem->size);
    > +}
    > +
    > +static uint64_t virtio_pmem_get_features(VirtIODevice *vdev, uint64_t features,
    > + Error **errp)
    > +{
    > + return features;
    > +}
    > +
    > +static void virtio_pmem_realize(DeviceState *dev, Error **errp)
    > +{
    > + VirtIODevice *vdev = VIRTIO_DEVICE(dev);
    > + VirtIOPMEM *pmem = VIRTIO_PMEM(dev);
    > + MachineState *ms = MACHINE(qdev_get_machine());
    > + uint64_t align;
    > + Error *local_err = NULL;
    > + MemoryRegion *mr;
    > +
    > + if (!pmem->memdev) {
    > + error_setg(errp, "virtio-pmem memdev not set");
    > + return;
    > + }
    > +
    > + mr = host_memory_backend_get_memory(pmem->memdev);
    > + align = memory_region_get_alignment(mr);
    > + pmem->size = QEMU_ALIGN_DOWN(memory_region_size(mr), align);
    > + pmem->start = memory_device_get_free_addr(ms, NULL, align, pmem->size,
    > + &local_err);
    > + if (local_err) {
    > + error_setg(errp, "Can't get free address in mem device");
    > + return;
    > + }
    > + memory_region_init_alias(&pmem->mr, OBJECT(pmem),
    > + "virtio_pmem-memory", mr, 0, pmem->size);
    > + memory_device_plug_region(ms, &pmem->mr, pmem->start);
    > +
    > + host_memory_backend_set_mapped(pmem->memdev, true);
    > + virtio_init(vdev, TYPE_VIRTIO_PMEM, VIRTIO_ID_PMEM,
    > + sizeof(struct virtio_pmem_config));
    > + pmem->rq_vq = virtio_add_queue(vdev, 128, virtio_pmem_flush);
    > +}
    > +
    > +static void virtio_mem_check_memdev(Object *obj, const char *name, Object *val,
    > + Error **errp)
    > +{
    > + if (host_memory_backend_is_mapped(MEMORY_BACKEND(val))) {
    > + char *path = object_get_canonical_path_component(val);
    > + error_setg(errp, "Can't use already busy memdev: %s", path);
    > + g_free(path);
    > + return;
    > + }
    > +
    > + qdev_prop_allow_set_link_before_realize(obj, name, val, errp);
    > +}
    > +
    > +static const char *virtio_pmem_get_device_id(VirtIOPMEM *vm)
    > +{
    > + Object *obj = OBJECT(vm);
    > + DeviceState *parent_dev;
    > +
    > + /* always use the ID of the proxy device */
    > + if (obj->parent && object_dynamic_cast(obj->parent, TYPE_DEVICE)) {
    > + parent_dev = DEVICE(obj->parent);
    > + return parent_dev->id;
    > + }
    > + return NULL;
    > +}
    > +
    > +static void virtio_pmem_md_fill_device_info(const MemoryDeviceState *md,
    > + MemoryDeviceInfo *info)
    > +{
    > + VirtioPMemDeviceInfo *vi = g_new0(VirtioPMemDeviceInfo, 1);
    > + VirtIOPMEM *vm = VIRTIO_PMEM(md);
    > + const char *id = virtio_pmem_get_device_id(vm);
    > +
    > + if (id) {
    > + vi->has_id = true;
    > + vi->id = g_strdup(id);
    > + }
    > +
    > + vi->start = vm->start;
    > + vi->size = vm->size;
    > + vi->memdev = object_get_canonical_path(OBJECT(vm->memdev));
    > +
    > + info->u.virtio_pmem.data = vi;
    > + info->type = MEMORY_DEVICE_INFO_KIND_VIRTIO_PMEM;
    > +}
    > +
    > +static uint64_t virtio_pmem_md_get_addr(const MemoryDeviceState *md)
    > +{
    > + VirtIOPMEM *vm = VIRTIO_PMEM(md);
    > +
    > + return vm->start;
    > +}
    > +
    > +static uint64_t virtio_pmem_md_get_plugged_size(const MemoryDeviceState *md)
    > +{
    > + VirtIOPMEM *vm = VIRTIO_PMEM(md);
    > +
    > + return vm->size;
    > +}
    > +
    > +static uint64_t virtio_pmem_md_get_region_size(const MemoryDeviceState *md)
    > +{
    > + VirtIOPMEM *vm = VIRTIO_PMEM(md);
    > +
    > + return vm->size;
    > +}
    > +
    > +static void virtio_pmem_instance_init(Object *obj)
    > +{
    > + VirtIOPMEM *vm = VIRTIO_PMEM(obj);
    > + object_property_add_link(obj, "memdev", TYPE_MEMORY_BACKEND,
    > + (Object **)&vm->memdev,
    > + (void *) virtio_mem_check_memdev,
    > + OBJ_PROP_LINK_STRONG,
    > + &error_abort);
    > +}
    > +
    > +
    > +static void virtio_pmem_class_init(ObjectClass *klass, void *data)
    > +{
    > + VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
    > + MemoryDeviceClass *mdc = MEMORY_DEVICE_CLASS(klass);
    > +
    > + vdc->realize = virtio_pmem_realize;
    > + vdc->get_config = virtio_pmem_get_config;
    > + vdc->get_features = virtio_pmem_get_features;
    > +
    > + mdc->get_addr = virtio_pmem_md_get_addr;
    > + mdc->get_plugged_size = virtio_pmem_md_get_plugged_size;
    > + mdc->get_region_size = virtio_pmem_md_get_region_size;
    > + mdc->fill_device_info = virtio_pmem_md_fill_device_info;
    > +}
    > +
    > +static TypeInfo virtio_pmem_info = {
    > + .name = TYPE_VIRTIO_PMEM,
    > + .parent = TYPE_VIRTIO_DEVICE,
    > + .class_init = virtio_pmem_class_init,
    > + .instance_size = sizeof(VirtIOPMEM),
    > + .instance_init = virtio_pmem_instance_init,
    > + .interfaces = (InterfaceInfo[]) {
    > + { TYPE_MEMORY_DEVICE },
    > + { }
    > + },
    > +};
    > +
    > +static void virtio_register_types(void)
    > +{
    > + type_register_static(&virtio_pmem_info);
    > +}
    > +
    > +type_init(virtio_register_types)
    > diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
    > index 990d6fcbde..28829b6437 100644
    > --- a/include/hw/pci/pci.h
    > +++ b/include/hw/pci/pci.h
    > @@ -85,6 +85,7 @@ extern bool pci_available;
    > #define PCI_DEVICE_ID_VIRTIO_RNG 0x1005
    > #define PCI_DEVICE_ID_VIRTIO_9P 0x1009
    > #define PCI_DEVICE_ID_VIRTIO_VSOCK 0x1012
    > +#define PCI_DEVICE_ID_VIRTIO_PMEM 0x1013
    >
    > #define PCI_VENDOR_ID_REDHAT 0x1b36
    > #define PCI_DEVICE_ID_REDHAT_BRIDGE 0x0001
    > diff --git a/include/hw/virtio/virtio-pmem.h b/include/hw/virtio/virtio-pmem.h
    > new file mode 100644
    > index 0000000000..fda3ee691c
    > --- /dev/null
    > +++ b/include/hw/virtio/virtio-pmem.h
    > @@ -0,0 +1,42 @@
    > +/*
    > + * Virtio pmem Device
    > + *
    > + * Copyright Red Hat, Inc. 2018
    > + * Copyright Pankaj Gupta <pagupta@redhat.com>
    > + *
    > + * This work is licensed under the terms of the GNU GPL, version 2 or
    > + * (at your option) any later version. See the COPYING file in the
    > + * top-level directory.
    > + */
    > +
    > +#ifndef QEMU_VIRTIO_PMEM_H
    > +#define QEMU_VIRTIO_PMEM_H
    > +
    > +#include "hw/virtio/virtio.h"
    > +#include "exec/memory.h"
    > +#include "sysemu/hostmem.h"
    > +#include "standard-headers/linux/virtio_ids.h"
    > +#include "hw/boards.h"
    > +#include "hw/i386/pc.h"
    > +
    > +#define TYPE_VIRTIO_PMEM "virtio-pmem"
    > +
    > +#define VIRTIO_PMEM(obj) \
    > + OBJECT_CHECK(VirtIOPMEM, (obj), TYPE_VIRTIO_PMEM)
    > +
    > +/* VirtIOPMEM device structure */
    > +typedef struct VirtIOPMEM {
    > + VirtIODevice parent_obj;
    > +
    > + VirtQueue *rq_vq;
    > + uint64_t start;
    > + uint64_t size;
    > + MemoryRegion mr;
    > + HostMemoryBackend *memdev;
    > +} VirtIOPMEM;
    > +
    > +struct virtio_pmem_config {
    > + uint64_t start;
    > + uint64_t size;
    > +};
    > +#endif
    > diff --git a/include/standard-headers/linux/virtio_ids.h b/include/standard-headers/linux/virtio_ids.h
    > index 6d5c3b2d4f..346389565a 100644
    > --- a/include/standard-headers/linux/virtio_ids.h
    > +++ b/include/standard-headers/linux/virtio_ids.h
    > @@ -43,5 +43,6 @@
    > #define VIRTIO_ID_INPUT 18 /* virtio input */
    > #define VIRTIO_ID_VSOCK 19 /* virtio vsock transport */
    > #define VIRTIO_ID_CRYPTO 20 /* virtio crypto */
    > +#define VIRTIO_ID_PMEM 25 /* virtio pmem */
    >
    > #endif /* _LINUX_VIRTIO_IDS_H */
    > diff --git a/qapi/misc.json b/qapi/misc.json
    > index d450cfef21..517376b866 100644
    > --- a/qapi/misc.json
    > +++ b/qapi/misc.json
    > @@ -2907,6 +2907,29 @@
    > }
    > }
    >
    > +##
    > +# @VirtioPMemDeviceInfo:
    > +#
    > +# VirtioPMem state information
    > +#
    > +# @id: device's ID
    > +#
    > +# @start: physical address, where device is mapped
    > +#
    > +# @size: size of memory that the device provides
    > +#
    > +# @memdev: memory backend linked with device
    > +#
    > +# Since: 3.1
    > +##
    > +{ 'struct': 'VirtioPMemDeviceInfo',
    > + 'data': { '*id': 'str',
    > + 'start': 'size',
    > + 'size': 'size',
    > + 'memdev': 'str'
    > + }
    > +}
    > +
    > ##
    > # @MemoryDeviceInfo:
    > #
    > @@ -2916,7 +2939,8 @@
    > ##
    > { 'union': 'MemoryDeviceInfo',
    > 'data': { 'dimm': 'PCDIMMDeviceInfo',
    > - 'nvdimm': 'PCDIMMDeviceInfo'
    > + 'nvdimm': 'PCDIMMDeviceInfo',
    > + 'virtio-pmem': 'VirtioPMemDeviceInfo'
    > }
    > }
    >

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