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    SubjectRe: [HMM 16/16] mm/hmm/devmem: dummy HMM device for ZONE_DEVICE memory v2
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    Hi Jérôme,

    On 2017/3/17 0:05, Jérôme Glisse wrote:
    > This introduce a dummy HMM device class so device driver can use it to
    > create hmm_device for the sole purpose of registering device memory.

    May I ask where is the latest dummy HMM device driver?
    I can only get this one: https://patchwork.kernel.org/patch/4352061/

    Thanks,
    Bob

    > It is usefull to device driver that want to manage multiple physical
    > device memory under same struct device umbrella.
    >
    > Changed since v1:
    > - Improve commit message
    > - Add drvdata parameter to set on struct device
    >
    > Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
    > Signed-off-by: Evgeny Baskakov <ebaskakov@nvidia.com>
    > Signed-off-by: John Hubbard <jhubbard@nvidia.com>
    > Signed-off-by: Mark Hairgrove <mhairgrove@nvidia.com>
    > Signed-off-by: Sherry Cheung <SCheung@nvidia.com>
    > Signed-off-by: Subhash Gutti <sgutti@nvidia.com>
    > ---
    > include/linux/hmm.h | 22 +++++++++++-
    > mm/hmm.c | 96 +++++++++++++++++++++++++++++++++++++++++++++++++++++
    > 2 files changed, 117 insertions(+), 1 deletion(-)
    >
    > diff --git a/include/linux/hmm.h b/include/linux/hmm.h
    > index 3054ce7..e4e6b36 100644
    > --- a/include/linux/hmm.h
    > +++ b/include/linux/hmm.h
    > @@ -79,11 +79,11 @@
    >
    > #if IS_ENABLED(CONFIG_HMM)
    >
    > +#include <linux/device.h>
    > #include <linux/migrate.h>
    > #include <linux/memremap.h>
    > #include <linux/completion.h>
    >
    > -
    > struct hmm;
    >
    > /*
    > @@ -433,6 +433,26 @@ static inline unsigned long hmm_devmem_page_get_drvdata(struct page *page)
    >
    > return drvdata[1];
    > }
    > +
    > +
    > +/*
    > + * struct hmm_device - fake device to hang device memory onto
    > + *
    > + * @device: device struct
    > + * @minor: device minor number
    > + */
    > +struct hmm_device {
    > + struct device device;
    > + unsigned minor;
    > +};
    > +
    > +/*
    > + * Device driver that wants to handle multiple devices memory through a single
    > + * fake device can use hmm_device to do so. This is purely a helper and it
    > + * is not needed to make use of any HMM functionality.
    > + */
    > +struct hmm_device *hmm_device_new(void *drvdata);
    > +void hmm_device_put(struct hmm_device *hmm_device);
    > #endif /* IS_ENABLED(CONFIG_HMM_DEVMEM) */
    >
    >
    > diff --git a/mm/hmm.c b/mm/hmm.c
    > index 019f379..c477bd1 100644
    > --- a/mm/hmm.c
    > +++ b/mm/hmm.c
    > @@ -24,6 +24,7 @@
    > #include <linux/slab.h>
    > #include <linux/sched.h>
    > #include <linux/mmzone.h>
    > +#include <linux/module.h>
    > #include <linux/pagemap.h>
    > #include <linux/swapops.h>
    > #include <linux/hugetlb.h>
    > @@ -1132,4 +1133,99 @@ int hmm_devmem_fault_range(struct hmm_devmem *devmem,
    > return 0;
    > }
    > EXPORT_SYMBOL(hmm_devmem_fault_range);
    > +
    > +/*
    > + * A device driver that wants to handle multiple devices memory through a
    > + * single fake device can use hmm_device to do so. This is purely a helper
    > + * and it is not needed to make use of any HMM functionality.
    > + */
    > +#define HMM_DEVICE_MAX 256
    > +
    > +static DECLARE_BITMAP(hmm_device_mask, HMM_DEVICE_MAX);
    > +static DEFINE_SPINLOCK(hmm_device_lock);
    > +static struct class *hmm_device_class;
    > +static dev_t hmm_device_devt;
    > +
    > +static void hmm_device_release(struct device *device)
    > +{
    > + struct hmm_device *hmm_device;
    > +
    > + hmm_device = container_of(device, struct hmm_device, device);
    > + spin_lock(&hmm_device_lock);
    > + clear_bit(hmm_device->minor, hmm_device_mask);
    > + spin_unlock(&hmm_device_lock);
    > +
    > + kfree(hmm_device);
    > +}
    > +
    > +struct hmm_device *hmm_device_new(void *drvdata)
    > +{
    > + struct hmm_device *hmm_device;
    > + int ret;
    > +
    > + hmm_device = kzalloc(sizeof(*hmm_device), GFP_KERNEL);
    > + if (!hmm_device)
    > + return ERR_PTR(-ENOMEM);
    > +
    > + ret = alloc_chrdev_region(&hmm_device->device.devt,0,1,"hmm_device");
    > + if (ret < 0) {
    > + kfree(hmm_device);
    > + return NULL;
    > + }
    > +
    > + spin_lock(&hmm_device_lock);
    > + hmm_device->minor=find_first_zero_bit(hmm_device_mask,HMM_DEVICE_MAX);
    > + if (hmm_device->minor >= HMM_DEVICE_MAX) {
    > + spin_unlock(&hmm_device_lock);
    > + kfree(hmm_device);
    > + return NULL;
    > + }
    > + set_bit(hmm_device->minor, hmm_device_mask);
    > + spin_unlock(&hmm_device_lock);
    > +
    > + dev_set_name(&hmm_device->device, "hmm_device%d", hmm_device->minor);
    > + hmm_device->device.devt = MKDEV(MAJOR(hmm_device_devt),
    > + hmm_device->minor);
    > + hmm_device->device.release = hmm_device_release;
    > + dev_set_drvdata(&hmm_device->device, drvdata);
    > + hmm_device->device.class = hmm_device_class;
    > + device_initialize(&hmm_device->device);
    > +
    > + return hmm_device;
    > +}
    > +EXPORT_SYMBOL(hmm_device_new);
    > +
    > +void hmm_device_put(struct hmm_device *hmm_device)
    > +{
    > + put_device(&hmm_device->device);
    > +}
    > +EXPORT_SYMBOL(hmm_device_put);
    > +
    > +static int __init hmm_init(void)
    > +{
    > + int ret;
    > +
    > + ret = alloc_chrdev_region(&hmm_device_devt, 0,
    > + HMM_DEVICE_MAX,
    > + "hmm_device");
    > + if (ret)
    > + return ret;
    > +
    > + hmm_device_class = class_create(THIS_MODULE, "hmm_device");
    > + if (IS_ERR(hmm_device_class)) {
    > + unregister_chrdev_region(hmm_device_devt, HMM_DEVICE_MAX);
    > + return PTR_ERR(hmm_device_class);
    > + }
    > + return 0;
    > +}
    > +
    > +static void __exit hmm_exit(void)
    > +{
    > + unregister_chrdev_region(hmm_device_devt, HMM_DEVICE_MAX);
    > + class_destroy(hmm_device_class);
    > +}
    > +
    > +module_init(hmm_init);
    > +module_exit(hmm_exit);
    > +MODULE_LICENSE("GPL");
    > #endif /* IS_ENABLED(CONFIG_HMM_DEVMEM) */
    >


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