1:44 a.m.
> This patch adds virtio-pmem driver for KVM
> guest.
>
> Guest reads the persistent memory range
> information from Qemu over VIRTIO and registers
> it on nvdimm_bus. It also creates a nd_region
> object with the persistent memory range
> information so that existing 'nvdimm/pmem'
> driver can reserve this into system memory map.
> This way 'virtio-pmem' driver uses existing
> functionality of pmem driver to register persistent
> memory compatible for DAX capable filesystems.
>
> This also provides function to perform guest flush
> over VIRTIO from 'pmem' driver when userspace
> performs flush on DAX memory range.
>
> Signed-off-by: Pankaj Gupta <pagupta(a)redhat.com>
> ---
> drivers/virtio/Kconfig | 12 ++++
> drivers/virtio/Makefile | 1 +
> drivers/virtio/virtio_pmem.c | 118
> +++++++++++++++++++++++++++++++++++++++
> include/linux/libnvdimm.h | 4 ++
> include/uapi/linux/virtio_ids.h | 1 +
> include/uapi/linux/virtio_pmem.h | 58 +++++++++++++++++++
> 6 files changed, 194 insertions(+)
> create mode 100644 drivers/virtio/virtio_pmem.c
> create mode 100644 include/uapi/linux/virtio_pmem.h
>
> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> index 3589764..879335d 100644
> --- a/drivers/virtio/Kconfig
> +++ b/drivers/virtio/Kconfig
> @@ -42,6 +42,18 @@ config VIRTIO_PCI_LEGACY
>
> If unsure, say Y.
>
> +config VIRTIO_PMEM
> + tristate "Virtio pmem driver"
> + depends on VIRTIO
> + help
> + This driver adds persistent memory range to nd_region and registers
> + with nvdimm bus. NVDIMM 'pmem' driver later allocates a persistent
> + memory range on the memory information added by this driver. In addition
> + to this, 'virtio-pmem' driver also provides a paravirt flushing
> interface
> + from guest to host.
> +
> + If unsure, say M.
> +
> config VIRTIO_BALLOON
> tristate "Virtio balloon driver"
> depends on VIRTIO
> diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile
> index 3a2b5c5..cbe91c6 100644
> --- a/drivers/virtio/Makefile
> +++ b/drivers/virtio/Makefile
> @@ -6,3 +6,4 @@ virtio_pci-y := virtio_pci_modern.o virtio_pci_common.o
> virtio_pci-$(CONFIG_VIRTIO_PCI_LEGACY) += virtio_pci_legacy.o
> obj-$(CONFIG_VIRTIO_BALLOON) += virtio_balloon.o
> obj-$(CONFIG_VIRTIO_INPUT) += virtio_input.o
> +obj-$(CONFIG_VIRTIO_PMEM) += virtio_pmem.o
> diff --git a/drivers/virtio/virtio_pmem.c b/drivers/virtio/virtio_pmem.c
> new file mode 100644
> index 0000000..0906d2d
> --- /dev/null
> +++ b/drivers/virtio/virtio_pmem.c
> @@ -0,0 +1,118 @@
SPDX license line? See Documentation/process/license-rules.rst.
o.k.
> +/* Virtio pmem Driver
> + *
> + * Discovers persitent memory range information
s/persitent/persistent/
> + * from host and provides a virtio based flushing
> + * interface.
> + */
> +
> +#include <linux/virtio.h>
> +#include <linux/swap.h>
> +#include <linux/workqueue.h>
> +#include <linux/delay.h>
> +#include <linux/slab.h>
> +#include <linux/module.h>
> +#include <linux/oom.h>
> +#include <linux/wait.h>
> +#include <linux/magic.h>
> +#include <linux/virtio_pmem.h>
> +#include <linux/libnvdimm.h>
Are all these headers really needed? delay.h? oom.h?
Will remove not required ones. There are from previous
RFC where used *memremap* and other mm & block includes.
> +
> +static int init_vq(struct virtio_pmem *vpmem)
> +{
> + struct virtqueue *vq;
> +
> + /* single vq */
> + vpmem->req_vq = vq = virtio_find_single_vq(vpmem->vdev,
> + NULL, "flush_queue");
> +
> + if (IS_ERR(vq))
> + return PTR_ERR(vq);
> +
> + return 0;
> +};
> +
> +static int virtio_pmem_probe(struct virtio_device *vdev)
> +{
> + int err = 0;
> + struct resource res;
> + struct virtio_pmem *vpmem;
> + struct nvdimm_bus *nvdimm_bus;
> + struct nd_region_desc ndr_desc;
> + int nid = dev_to_node(&vdev->dev);
> + static struct nvdimm_bus_descriptor nd_desc;
> +
> + if (!vdev->config->get) {
> + dev_err(&vdev->dev, "%s failure: config disabled\n",
> + __func__);
> + return -EINVAL;
> + }
> +
> + vdev->priv = vpmem = devm_kzalloc(&vdev->dev, sizeof(*vpmem),
> + GFP_KERNEL);
> + if (!vpmem) {
> + err = -ENOMEM;
> + goto out;
> + }
> +
> + vpmem->vdev = vdev;
> + err = init_vq(vpmem);
> + if (err)
> + goto out;
> +
> + virtio_cread(vpmem->vdev, struct virtio_pmem_config,
> + start, &vpmem->start);
> + virtio_cread(vpmem->vdev, struct virtio_pmem_config,
> + size, &vpmem->size);
> +
> + res.start = vpmem->start;
> + res.end = vpmem->start + vpmem->size-1;
> +
> + memset(&nd_desc, 0, sizeof(nd_desc));
> + nd_desc.provider_name = "virtio-pmem";
> + nd_desc.module = THIS_MODULE;
> + nvdimm_bus = nvdimm_bus_register(&vdev->dev, &nd_desc);
> +
> + if (!nvdimm_bus)
> + goto out_nd;
> + dev_set_drvdata(&vdev->dev, nvdimm_bus);
> +
> + memset(&ndr_desc, 0, sizeof(ndr_desc));
> + ndr_desc.res = &res;
> + ndr_desc.numa_node = nid;
> + set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
> + set_bit(ND_REGION_VIRTIO, &ndr_desc.flags);
> +
> + if (!nvdimm_pmem_region_create(nvdimm_bus, &ndr_desc))
> + goto out_nd;
> +
> + virtio_device_ready(vdev);
> + return 0;
> +
> +out_nd:
> + nvdimm_bus_unregister(nvdimm_bus);
> +out:
> + dev_err(&vdev->dev, "failed to register virtio pmem memory\n");
> + vdev->config->del_vqs(vdev);
> + return err;
> +}
> +
> +static void virtio_pmem_remove(struct virtio_device *vdev)
> +{
> + struct nvdimm_bus *nvdimm_bus = dev_get_drvdata(&vdev->dev);
> +
> + nvdimm_bus_unregister(nvdimm_bus);
> + vdev->config->del_vqs(vdev);
> +}
> +
> +static struct virtio_driver virtio_pmem_driver = {
> + .driver.name = KBUILD_MODNAME,
> + .driver.owner = THIS_MODULE,
> + .id_table = id_table,
> + .probe = virtio_pmem_probe,
> + .remove = virtio_pmem_remove,
> +};
> +
> +module_virtio_driver(virtio_pmem_driver);
> +MODULE_DEVICE_TABLE(virtio, id_table);
> +MODULE_DESCRIPTION("Virtio pmem driver");
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
> index 097072c..b1b7f14 100644
> --- a/include/linux/libnvdimm.h
> +++ b/include/linux/libnvdimm.h
> @@ -58,6 +58,10 @@ enum {
> * (ADR)
> */
> ND_REGION_PERSIST_MEMCTRL = 2,
> + /*
> + * region flag indicating to use VIRTIO flush interface for pmem
> + */
> + ND_REGION_VIRTIO = 3,
Can you add a generic flush callback to libnvdimm instead? That way
virtio and other drivers can hook in without hardcoding knowledge of
these drivers into libnvdimm.
Sure! Working on this. Same suggestion by Dan.
>
> /* mark newly adjusted resources as requiring a label update */
> DPA_RESOURCE_ADJUSTED = 1 << 0,
> diff --git a/include/uapi/linux/virtio_ids.h
> b/include/uapi/linux/virtio_ids.h
> index 6d5c3b2..5ebd049 100644
> --- a/include/uapi/linux/virtio_ids.h
> +++ b/include/uapi/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 21 /* virtio pmem */
>
> #endif /* _LINUX_VIRTIO_IDS_H */
> diff --git a/include/uapi/linux/virtio_pmem.h
> b/include/uapi/linux/virtio_pmem.h
> new file mode 100644
> index 0000000..2ec27cb
> --- /dev/null
> +++ b/include/uapi/linux/virtio_pmem.h
> @@ -0,0 +1,58 @@
> +/* Virtio pmem Driver
> + *
> + * Discovers persitent memory range information
s/persitent/persistent/
> + * from host and provides a virtio based flushing
> + * interface.
> + */
> +
> +#ifndef _LINUX_VIRTIO_PMEM_H
> +#define _LINUX_VIRTIO_PMEM_H
> +
> +#include <linux/types.h>
> +#include <linux/virtio_types.h>
> +#include <linux/virtio_ids.h>
> +#include <linux/virtio_config.h>
> +#include <linux/virtio_ring.h>
> +
> +
> +struct virtio_pmem_config {
> +
> + uint64_t start;
> + uint64_t size;
> +};
> +
> +struct virtio_pmem {
> +
> + struct virtio_device *vdev;
> + struct virtqueue *req_vq;
> +
> + uint64_t start;
> + uint64_t size;
> +} __packed;
This is a userspace API header file, it should contain definitions that
userspace programs need. struct virtio_pmem is a kernel-internal struct
that should not be in the uapi headers.
Only define virtio spec structs in this header file (e.g. config space,
request structs, etc).
o.k
> +static struct virtio_device_id id_table[] = {
> + { VIRTIO_ID_PMEM, VIRTIO_DEV_ANY_ID },
> + { 0 },
> +};
Why is static variable in the header file?
mistake :)
> +
> +void virtio_pmem_flush(struct device *dev)
This only implements flush command submission, not completion. Maybe
the next patch will implement that but it's a little strange to only see
half of the flush operation.
Please put the whole flush operation in one patch so it can be reviewed
easily. At this point I don't know if you've forgotten to implement
wait for completion.
> +{
Why is this function body in the header file?
Because I was trying to use it from pmem module without loading
virtio_pmem driver or load it dynamically. I think adding flush function in
'nd_region' struct and set it as per region type looks better solution.
Suggested by Dan & you.
> + struct scatterlist sg;
> + struct virtio_device *vdev = dev_to_virtio(dev->parent->parent);
> + struct virtio_pmem *vpmem = vdev->priv;
> + char *buf = "FLUSH";
I'm surprised this compiles without a warning. String literals should
be constant but the char pointer isn't constant.
Point taken.
> + int err;
> +
> + sg_init_one(&sg, buf, sizeof(buf));
> +
> + err = virtqueue_add_outbuf(vpmem->req_vq, &sg, 1, buf, GFP_KERNEL);
> +
> + if (err) {
> + dev_err(&vdev->dev, "failed to send command to virtio pmem
device\n");
> + return;
> + }
> +
> + virtqueue_kick(vpmem->req_vq);
Is any locking necessary? Two CPUs must not invoke virtio_pmem_flush()
at the same time. Not sure if anything guarantees this, maybe you're
relying on libnvdimm but I haven't checked.
I thought about it to some extent, and wanted to go ahead with simple version first:
- I think file 'inode -> locking' sill is there for request on single file.
- For multiple files, our aim is to just flush the backend block image.
- Even there is collision for virt queue read/write entry it should just trigger a Qemu
fsync.
We just want most recent flush to assure guest writes are synced properly.
Important point here: We are doing entire block fsync for guest virtual disk.
> +};
> +
> +#endif
> --
> 2.9.3
>
>