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Subject[HMM v13 18/18] mm/hmm/devmem: dummy HMM device as an helper for ZONE_DEVICE memory
Date
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.
It is usefull to device driver that want to manage multiple physical
device memory under same device umbrella.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Jatin Kumar <jakumar@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 | 95 +++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 116 insertions(+), 1 deletion(-)

diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index ac0b69a..106de1f 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -88,10 +88,10 @@

#if IS_ENABLED(CONFIG_HMM)

+#include <linux/device.h>
#include <linux/memremap.h>
#include <linux/completion.h>

-
struct hmm;

/*
@@ -484,6 +484,26 @@ static inline unsigned long hmm_devmem_page_get_drvdata(struct page *page)
}


+/*
+ * 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 want to handle multiple devices memory through a single
+ * fake device can use hmm_device to do so. This is purely an helper and it
+ * is not needed to make use of any HMM functionality.
+ */
+struct hmm_device *hmm_device_new(void);
+void hmm_device_put(struct hmm_device *hmm_device);
+
+
/* Below are for HMM internal use only ! Not to be use by device driver ! */
void hmm_mm_destroy(struct mm_struct *mm);

diff --git a/mm/hmm.c b/mm/hmm.c
index f2ca895..61c3640187 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>
@@ -1078,3 +1079,97 @@ int hmm_devmem_fault_range(struct hmm_devmem *devmem,
return 0;
}
EXPORT_SYMBOL(hmm_devmem_fault_range);
+
+/*
+ * Device driver that want to handle multiple devices memory through a single
+ * fake device can use hmm_device to do so. This is purely an 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)
+{
+ 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;
+ 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");
--
2.4.3
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