Message-ID: <e3163e6a-654d-cbf6-3aad-788c31f20655@huawei.com>
Date:   Fri, 17 Mar 2017 14:55:57 +0800
From:   Bob Liu <liubo95@...wei.com>
To:     Jérôme Glisse <jglisse@...hat.com>,
        <akpm@...ux-foundation.org>, <linux-kernel@...r.kernel.org>,
        <linux-mm@...ck.org>
CC:     John Hubbard <jhubbard@...dia.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        David Nellans <dnellans@...dia.com>,
        "Evgeny Baskakov" <ebaskakov@...dia.com>,
        Mark Hairgrove <mhairgrove@...dia.com>,
        Sherry Cheung <SCheung@...dia.com>,
        Subhash Gutti <sgutti@...dia.com>
Subject: Re: [HMM 16/16] mm/hmm/devmem: dummy HMM device for ZONE_DEVICE
 memory v2

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@...hat.com>
> Signed-off-by: Evgeny Baskakov <ebaskakov@...dia.com>
> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> Signed-off-by: Mark Hairgrove <mhairgrove@...dia.com>
> Signed-off-by: Sherry Cheung <SCheung@...dia.com>
> Signed-off-by: Subhash Gutti <sgutti@...dia.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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