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Date: Tue, 8 Mar 2022 14:10:09 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: mpenttil@...hat.com, linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Cc: Jérôme Glisse <jglisse@...hat.com>,
Alistair Popple <apopple@...dia.com>,
Ralph Campbell <rcampbell@...dia.com>,
Jason Gunthorpe <jgg@...pe.ca>,
John Hubbard <jhubbard@...dia.com>
Subject: Re: [PATCH] HMM selftests changes
+CC relevant folks
On 3/8/22 02:57, mpenttil@...hat.com wrote:
> From: Mika Penttilä <mpenttil@...hat.com>
>
> HMM selftests use a in-kernel pseudo device to emulate device private memory.
>
> For now, the pseudo device registers a major device range for two pseudo device instances.
> User space has a script that goes figures out from /proc/devices the assigned major
> and mknods the device nodes.
>
> Change this use to a more standard device framework, like misc device,
> which makes the device node names to appear right under any decent user space.
> This also makes it possible for udev- like processing if wanted,
> and the /proc/devices parsing is not needed any more.
>
> Signed-off-by: Mika Penttilä <mpenttil@...hat.com>
> ---
> lib/test_hmm.c | 46 +++++++++++++++-----------
> tools/testing/selftests/vm/test_hmm.sh | 6 ----
> 2 files changed, 26 insertions(+), 26 deletions(-)
>
> diff --git a/lib/test_hmm.c b/lib/test_hmm.c
> index 767538089a62..76f6129e1f1f 100644
> --- a/lib/test_hmm.c
> +++ b/lib/test_hmm.c
> @@ -10,7 +10,6 @@
> #include <linux/mm.h>
> #include <linux/module.h>
> #include <linux/kernel.h>
> -#include <linux/cdev.h>
> #include <linux/device.h>
> #include <linux/mutex.h>
> #include <linux/rwsem.h>
> @@ -25,18 +24,25 @@
> #include <linux/swapops.h>
> #include <linux/sched/mm.h>
> #include <linux/platform_device.h>
> +#include <linux/miscdevice.h>
> #include <linux/rmap.h>
>
> #include "test_hmm_uapi.h"
>
> -#define DMIRROR_NDEVICES 2
> #define DMIRROR_RANGE_FAULT_TIMEOUT 1000
> #define DEVMEM_CHUNK_SIZE (256 * 1024 * 1024U)
> #define DEVMEM_CHUNKS_RESERVE 16
>
> +
> +static const char *dmirror_device_names[] = {
> + "hmm_dmirror0",
> + "hmm_dmirror1"
> +};
> +
> +#define DMIRROR_NDEVICES ARRAY_SIZE(dmirror_device_names)
> +
> static const struct dev_pagemap_ops dmirror_devmem_ops;
> static const struct mmu_interval_notifier_ops dmirror_min_ops;
> -static dev_t dmirror_dev;
>
> struct dmirror_device;
>
> @@ -82,7 +88,7 @@ struct dmirror_chunk {
> * Per device data.
> */
> struct dmirror_device {
> - struct cdev cdevice;
> + struct miscdevice miscdevice;
> struct hmm_devmem *devmem;
>
> unsigned int devmem_capacity;
> @@ -118,16 +124,20 @@ static void dmirror_bounce_fini(struct dmirror_bounce *bounce)
>
> static int dmirror_fops_open(struct inode *inode, struct file *filp)
> {
> - struct cdev *cdev = inode->i_cdev;
> +
> + struct dmirror_device *dd = container_of(filp->private_data,
> + struct dmirror_device, miscdevice
> + );
> struct dmirror *dmirror;
> int ret;
>
> +
> /* Mirror this process address space */
> dmirror = kzalloc(sizeof(*dmirror), GFP_KERNEL);
> if (dmirror == NULL)
> return -ENOMEM;
>
> - dmirror->mdevice = container_of(cdev, struct dmirror_device, cdevice);
> + dmirror->mdevice = dd;
> mutex_init(&dmirror->mutex);
> xa_init(&dmirror->pt);
>
> @@ -1216,16 +1226,18 @@ static const struct dev_pagemap_ops dmirror_devmem_ops = {
>
> static int dmirror_device_init(struct dmirror_device *mdevice, int id)
> {
> - dev_t dev;
> +
> int ret;
>
> - dev = MKDEV(MAJOR(dmirror_dev), id);
> mutex_init(&mdevice->devmem_lock);
> spin_lock_init(&mdevice->lock);
>
> - cdev_init(&mdevice->cdevice, &dmirror_fops);
> - mdevice->cdevice.owner = THIS_MODULE;
> - ret = cdev_add(&mdevice->cdevice, dev, 1);
> + mdevice->miscdevice.minor = MISC_DYNAMIC_MINOR;
> + mdevice->miscdevice.name = dmirror_device_names[id];
> + mdevice->miscdevice.fops = &dmirror_fops;
> +
> + ret = misc_register(&mdevice->miscdevice);
> +
> if (ret)
> return ret;
>
> @@ -1252,7 +1264,7 @@ static void dmirror_device_remove(struct dmirror_device *mdevice)
> kfree(mdevice->devmem_chunks);
> }
>
> - cdev_del(&mdevice->cdevice);
> + misc_deregister(&mdevice->miscdevice);
> }
>
> static int __init hmm_dmirror_init(void)
> @@ -1260,11 +1272,6 @@ static int __init hmm_dmirror_init(void)
> int ret;
> int id;
>
> - ret = alloc_chrdev_region(&dmirror_dev, 0, DMIRROR_NDEVICES,
> - "HMM_DMIRROR");
> - if (ret)
> - goto err_unreg;
> -
> for (id = 0; id < DMIRROR_NDEVICES; id++) {
> ret = dmirror_device_init(dmirror_devices + id, id);
> if (ret)
> @@ -1277,8 +1284,7 @@ static int __init hmm_dmirror_init(void)
> err_chrdev:
> while (--id >= 0)
> dmirror_device_remove(dmirror_devices + id);
> - unregister_chrdev_region(dmirror_dev, DMIRROR_NDEVICES);
> -err_unreg:
> +
> return ret;
> }
>
> @@ -1288,7 +1294,7 @@ static void __exit hmm_dmirror_exit(void)
>
> for (id = 0; id < DMIRROR_NDEVICES; id++)
> dmirror_device_remove(dmirror_devices + id);
> - unregister_chrdev_region(dmirror_dev, DMIRROR_NDEVICES);
> +
> }
>
> module_init(hmm_dmirror_init);
> diff --git a/tools/testing/selftests/vm/test_hmm.sh b/tools/testing/selftests/vm/test_hmm.sh
> index 0647b525a625..69f5889f8575 100755
> --- a/tools/testing/selftests/vm/test_hmm.sh
> +++ b/tools/testing/selftests/vm/test_hmm.sh
> @@ -41,17 +41,11 @@ check_test_requirements()
> load_driver()
> {
> modprobe $DRIVER > /dev/null 2>&1
> - if [ $? == 0 ]; then
> - major=$(awk "\$2==\"HMM_DMIRROR\" {print \$1}" /proc/devices)
> - mknod /dev/hmm_dmirror0 c $major 0
> - mknod /dev/hmm_dmirror1 c $major 1
> - fi
> }
>
> unload_driver()
> {
> modprobe -r $DRIVER > /dev/null 2>&1
> - rm -f /dev/hmm_dmirror?
> }
>
> run_smoke()
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