Re: [Qemu-devel] [PATCH v4 2/5] virtio-pmem: Add virtio pmem driver
On Wed, Apr 03, 2019 at 08:40:13AM -0400, Pankaj Gupta wrote:
>
> > Subject: Re: [Qemu-devel] [PATCH v4 2/5] virtio-pmem: Add virtio pmem driver
> >
> > On Wed, Apr 03, 2019 at 04:10:15PM +0530, Pankaj Gupta wrote:
> > > 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
> > > ---
> > > drivers/nvdimm/virtio_pmem.c | 84 +
> > > drivers/virtio/Kconfig | 10 +++
> > > drivers/virtio/Makefile | 1 +
> > > drivers/virtio/pmem.c| 125 +++
> > > include/linux/virtio_pmem.h | 60 +++
> > > include/uapi/linux/virtio_ids.h | 1 +
> > > include/uapi/linux/virtio_pmem.h | 10 +++
> > > 7 files changed, 291 insertions(+)
> > > create mode 100644 drivers/nvdimm/virtio_pmem.c
> > > create mode 100644 drivers/virtio/pmem.c
> > > create mode 100644 include/linux/virtio_pmem.h
> > > create mode 100644 include/uapi/linux/virtio_pmem.h
> > >
> > > diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
> > > new file mode 100644
> > > index ..2a1b1ba2c1ff
> > > --- /dev/null
> > > +++ b/drivers/nvdimm/virtio_pmem.c
> > > @@ -0,0 +1,84 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> >
> > Is this comment stile (//) acceptable?
>
> In existing code, i can see same comment
> pattern for license at some places.
Is it preferred for new code?
>
> >
> > > +/*
> > > + * virtio_pmem.c: Virtio pmem Driver
> > > + *
> > > + * Discovers persistent memory range information
> > > + * from host and provides a virtio based flushing
> > > + * interface.
> > > + */
> > > +#include
> > > +#include "nd.h"
> > > +
> > > + /* The interrupt handler */
> > > +void host_ack(struct virtqueue *vq)
> > > +{
> > > + unsigned int len;
> > > + unsigned long flags;
> > > + struct virtio_pmem_request *req, *req_buf;
> > > + struct virtio_pmem *vpmem = vq->vdev->priv;
> > > +
> > > + spin_lock_irqsave(&vpmem->pmem_lock, flags);
> > > + while ((req = virtqueue_get_buf(vq, &len)) != NULL) {
> > > + req->done = true;
> > > + wake_up(&req->host_acked);
> > > +
> > > + if (!list_empty(&vpmem->req_list)) {
> > > + req_buf = list_first_entry(&vpmem->req_list,
> > > + struct virtio_pmem_request, list);
> > > + list_del(&vpmem->req_list);
> > > + req_buf->wq_buf_avail = true;
> > > + wake_up(&req_buf->wq_buf);
> > > + }
> > > + }
> > > + spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
> > > +}
> > > +EXPORT_SYMBOL_GPL(host_ack);
> > > +
> > > + /* The request submission function */
> > > +int virtio_pmem_flush(struct nd_region *nd_region)
> > > +{
> > > + int err;
> > > + unsigned long flags;
> > > + struct scatterlist *sgs[2], sg, ret;
> > > + struct virtio_device *vdev = nd_region->provider_data;
> > > + struct virtio_pmem *vpmem = vdev->priv;
> > > + struct virtio_pmem_request *req;
> > > +
> > > + might_sleep();
> >
> > [1]
> >
> > > + req = kmalloc(sizeof(*req), GFP_KERNEL);
> > > + if (!req)
> > > + return -ENOMEM;
> > > +
> > > + req->done = req->wq_buf_avail = false;
> > > + strcpy(req->name, "FLUSH");
> > > + init_waitqueue_head(&req->host_acked);
> > > + init_waitqueue_head(&req->wq_buf);
> &
Re: [Qemu-devel] [PATCH v4 2/5] virtio-pmem: Add virtio pmem driver
On Wed, Apr 03, 2019 at 04:10:15PM +0530, Pankaj Gupta wrote:
> 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
> ---
> drivers/nvdimm/virtio_pmem.c | 84 +
> drivers/virtio/Kconfig | 10 +++
> drivers/virtio/Makefile | 1 +
> drivers/virtio/pmem.c| 125 +++
> include/linux/virtio_pmem.h | 60 +++
> include/uapi/linux/virtio_ids.h | 1 +
> include/uapi/linux/virtio_pmem.h | 10 +++
> 7 files changed, 291 insertions(+)
> create mode 100644 drivers/nvdimm/virtio_pmem.c
> create mode 100644 drivers/virtio/pmem.c
> create mode 100644 include/linux/virtio_pmem.h
> create mode 100644 include/uapi/linux/virtio_pmem.h
>
> diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
> new file mode 100644
> index ..2a1b1ba2c1ff
> --- /dev/null
> +++ b/drivers/nvdimm/virtio_pmem.c
> @@ -0,0 +1,84 @@
> +// SPDX-License-Identifier: GPL-2.0
Is this comment stile (//) acceptable?
> +/*
> + * virtio_pmem.c: Virtio pmem Driver
> + *
> + * Discovers persistent memory range information
> + * from host and provides a virtio based flushing
> + * interface.
> + */
> +#include
> +#include "nd.h"
> +
> + /* The interrupt handler */
> +void host_ack(struct virtqueue *vq)
> +{
> + unsigned int len;
> + unsigned long flags;
> + struct virtio_pmem_request *req, *req_buf;
> + struct virtio_pmem *vpmem = vq->vdev->priv;
> +
> + spin_lock_irqsave(&vpmem->pmem_lock, flags);
> + while ((req = virtqueue_get_buf(vq, &len)) != NULL) {
> + req->done = true;
> + wake_up(&req->host_acked);
> +
> + if (!list_empty(&vpmem->req_list)) {
> + req_buf = list_first_entry(&vpmem->req_list,
> + struct virtio_pmem_request, list);
> + list_del(&vpmem->req_list);
> + req_buf->wq_buf_avail = true;
> + wake_up(&req_buf->wq_buf);
> + }
> + }
> + spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
> +}
> +EXPORT_SYMBOL_GPL(host_ack);
> +
> + /* The request submission function */
> +int virtio_pmem_flush(struct nd_region *nd_region)
> +{
> + int err;
> + unsigned long flags;
> + struct scatterlist *sgs[2], sg, ret;
> + struct virtio_device *vdev = nd_region->provider_data;
> + struct virtio_pmem *vpmem = vdev->priv;
> + struct virtio_pmem_request *req;
> +
> + might_sleep();
[1]
> + req = kmalloc(sizeof(*req), GFP_KERNEL);
> + if (!req)
> + return -ENOMEM;
> +
> + req->done = req->wq_buf_avail = false;
> + strcpy(req->name, "FLUSH");
> + init_waitqueue_head(&req->host_acked);
> + init_waitqueue_head(&req->wq_buf);
> + sg_init_one(&sg, req->name, strlen(req->name));
> + sgs[0] = &sg;
> + sg_init_one(&ret, &req->ret, sizeof(req->ret));
> + sgs[1] = &ret;
> +
> + spin_lock_irqsave(&vpmem->pmem_lock, flags);
> + err = virtqueue_add_sgs(vpmem->req_vq, sgs, 1, 1, req, GFP_ATOMIC);
Is it okay to use GFP_ATOMIC in a might-sleep ([1]) function?
> + if (err) {
> + dev_err(&vdev->dev, "failed to send command to virtio pmem
> device\n");
> +
> + list_add_tail(&vpmem->req_list, &req->list);
> + spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
> +
> + /* When host has read buffer, this completes via host_ack */
> + wait_event(req->wq_buf, req->wq_buf_avail);
> + spin_lock_irqsave(&vpmem->pmem_lock, flags);
> + }
> + virtqueue_kick(vpmem->req_vq);
You probably want to check return value here.
> + spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
> +
> + /* When host has read buffer, this completes via host_ack */
> + wait_event(req->host_acked, req->done);
> + err = req->ret;
> + kfree(req);
> +
> + return err;
> +};
> +EXPORT_SYMBOL_GPL(virtio_pmem_flush);
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> index 35897649c24f..9f634a2ed638 100644
> --- a/drivers/virtio/Kconfig
> +++ b/drivers/virtio/Kconfig
> @@ -42,6 +42,16 @@ config VIRTIO_PCI_LEGACY
>
> If unsure, say Y.
>
> +config VIRTIO_PMEM
> + tristate "Support for virtio pmem driver"
> + depends on VIRTIO
> + depends on LIBNVDIMM
Re: [Qemu-devel] [PATCH v4 2/5] virtio-pmem: Add virtio pmem driver
> >
> > > Subject: Re: [Qemu-devel] [PATCH v4 2/5] virtio-pmem: Add virtio pmem
> > > driver
> > >
> > > On Wed, Apr 03, 2019 at 04:10:15PM +0530, Pankaj Gupta wrote:
> > > > 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
> > > > ---
> > > > drivers/nvdimm/virtio_pmem.c | 84 +
> > > > drivers/virtio/Kconfig | 10 +++
> > > > drivers/virtio/Makefile | 1 +
> > > > drivers/virtio/pmem.c| 125 +++
> > > > include/linux/virtio_pmem.h | 60 +++
> > > > include/uapi/linux/virtio_ids.h | 1 +
> > > > include/uapi/linux/virtio_pmem.h | 10 +++
> > > > 7 files changed, 291 insertions(+)
> > > > create mode 100644 drivers/nvdimm/virtio_pmem.c
> > > > create mode 100644 drivers/virtio/pmem.c
> > > > create mode 100644 include/linux/virtio_pmem.h
> > > > create mode 100644 include/uapi/linux/virtio_pmem.h
> > > >
> > > > diff --git a/drivers/nvdimm/virtio_pmem.c
> > > > b/drivers/nvdimm/virtio_pmem.c
> > > > new file mode 100644
> > > > index ..2a1b1ba2c1ff
> > > > --- /dev/null
> > > > +++ b/drivers/nvdimm/virtio_pmem.c
> > > > @@ -0,0 +1,84 @@
> > > > +// SPDX-License-Identifier: GPL-2.0
> > >
> > > Is this comment stile (//) acceptable?
> >
> > In existing code, i can see same comment
> > pattern for license at some places.
>
> Is it preferred for new code?
will change.
>
> >
> > >
> > > > +/*
> > > > + * virtio_pmem.c: Virtio pmem Driver
> > > > + *
> > > > + * Discovers persistent memory range information
> > > > + * from host and provides a virtio based flushing
> > > > + * interface.
> > > > + */
> > > > +#include
> > > > +#include "nd.h"
> > > > +
> > > > + /* The interrupt handler */
> > > > +void host_ack(struct virtqueue *vq)
> > > > +{
> > > > + unsigned int len;
> > > > + unsigned long flags;
> > > > + struct virtio_pmem_request *req, *req_buf;
> > > > + struct virtio_pmem *vpmem = vq->vdev->priv;
> > > > +
> > > > + spin_lock_irqsave(&vpmem->pmem_lock, flags);
> > > > + while ((req = virtqueue_get_buf(vq, &len)) != NULL) {
> > > > + req->done = true;
> > > > + wake_up(&req->host_acked);
> > > > +
> > > > + if (!list_empty(&vpmem->req_list)) {
> > > > + req_buf = list_first_entry(&vpmem->req_list,
> > > > + struct virtio_pmem_request,
> > > > list);
> > > > + list_del(&vpmem->req_list);
> > > > + req_buf->wq_buf_avail = true;
> > > > + wake_up(&req_buf->wq_buf);
> > > > + }
> > > > + }
> > > > + spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
> > > > +}
> > > > +EXPORT_SYMBOL_GPL(host_ack);
> > > > +
> > > > + /* The request submission function */
> > > > +int virtio_pmem_flush(struct nd_region *nd_region)
> > > > +{
> > > > + int err;
> > > > + unsigned long flags;
> > > > + struct scatterlist *sgs[2], sg, ret;
> > > > + struct virtio_device
Re: [Qemu-devel] [PATCH v4 2/5] virtio-pmem: Add virtio pmem driver
> Subject: Re: [Qemu-devel] [PATCH v4 2/5] virtio-pmem: Add virtio pmem driver
>
> On Wed, Apr 03, 2019 at 04:10:15PM +0530, Pankaj Gupta wrote:
> > 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
> > ---
> > drivers/nvdimm/virtio_pmem.c | 84 +
> > drivers/virtio/Kconfig | 10 +++
> > drivers/virtio/Makefile | 1 +
> > drivers/virtio/pmem.c| 125 +++
> > include/linux/virtio_pmem.h | 60 +++
> > include/uapi/linux/virtio_ids.h | 1 +
> > include/uapi/linux/virtio_pmem.h | 10 +++
> > 7 files changed, 291 insertions(+)
> > create mode 100644 drivers/nvdimm/virtio_pmem.c
> > create mode 100644 drivers/virtio/pmem.c
> > create mode 100644 include/linux/virtio_pmem.h
> > create mode 100644 include/uapi/linux/virtio_pmem.h
> >
> > diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
> > new file mode 100644
> > index ..2a1b1ba2c1ff
> > --- /dev/null
> > +++ b/drivers/nvdimm/virtio_pmem.c
> > @@ -0,0 +1,84 @@
> > +// SPDX-License-Identifier: GPL-2.0
>
> Is this comment stile (//) acceptable?
In existing code, i can see same comment
pattern for license at some places.
>
> > +/*
> > + * virtio_pmem.c: Virtio pmem Driver
> > + *
> > + * Discovers persistent memory range information
> > + * from host and provides a virtio based flushing
> > + * interface.
> > + */
> > +#include
> > +#include "nd.h"
> > +
> > + /* The interrupt handler */
> > +void host_ack(struct virtqueue *vq)
> > +{
> > + unsigned int len;
> > + unsigned long flags;
> > + struct virtio_pmem_request *req, *req_buf;
> > + struct virtio_pmem *vpmem = vq->vdev->priv;
> > +
> > + spin_lock_irqsave(&vpmem->pmem_lock, flags);
> > + while ((req = virtqueue_get_buf(vq, &len)) != NULL) {
> > + req->done = true;
> > + wake_up(&req->host_acked);
> > +
> > + if (!list_empty(&vpmem->req_list)) {
> > + req_buf = list_first_entry(&vpmem->req_list,
> > + struct virtio_pmem_request, list);
> > + list_del(&vpmem->req_list);
> > + req_buf->wq_buf_avail = true;
> > + wake_up(&req_buf->wq_buf);
> > + }
> > + }
> > + spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
> > +}
> > +EXPORT_SYMBOL_GPL(host_ack);
> > +
> > + /* The request submission function */
> > +int virtio_pmem_flush(struct nd_region *nd_region)
> > +{
> > + int err;
> > + unsigned long flags;
> > + struct scatterlist *sgs[2], sg, ret;
> > + struct virtio_device *vdev = nd_region->provider_data;
> > + struct virtio_pmem *vpmem = vdev->priv;
> > + struct virtio_pmem_request *req;
> > +
> > + might_sleep();
>
> [1]
>
> > + req = kmalloc(sizeof(*req), GFP_KERNEL);
> > + if (!req)
> > + return -ENOMEM;
> > +
> > + req->done = req->wq_buf_avail = false;
> > + strcpy(req->name, "FLUSH");
> > + init_waitqueue_head(&req->host_acked);
> > + init_waitqueue_head(&req->wq_buf);
> > + sg_init_one(&sg, req->name, strlen(req->name));
> > + sgs[0] = &sg;
> > + sg_init_one(&ret, &req->ret, sizeof(req->ret));
> > + sgs[1] = &ret;
> > +
> > + spin_lock_irqsave(&vpmem->pmem_lock, flags);
> > + err = virtqueue_add_sgs(vpmem->req_vq, sgs, 1, 1, req, GFP_ATOMIC);
>
> Is it okay to use GFP_ATOMIC in a might-sleep ([1]) function?
might sleep will give us a warning if we try to sleep from non-sleepable
context.
We are doing it other way, i.e might_sl
