Subject: Re: [PATCH v3 3/9] powerpc/vas: Add VAS user space API

From: Daniel Axtens <[email-masked]>
Date: Wed, 18 Mar 2020 18:12:25 +1100

Haren Myneni <[email-masked]> writes:

> On power9, userspace can send GZIP compression requests directly to NX
> once kernel establishes NX channel / window with VAS. This patch provides
> user space API which allows user space to establish channel using open
> VAS_TX_WIN_OPEN ioctl, mmap and close operations.
>
> Each window corresponds to file descriptor and application can open
> multiple windows. After the window is opened, VAS_TX_WIN_OPEN icoctl to
> open a window on specific VAS instance, mmap() system call to map
> the hardware address of engine's request queue into the application's
> virtual address space.
>
> Then the application can then submit one or more requests to the the
> engine by using the copy/paste instructions and pasting the CRBs to
> the virtual address (aka paste_address) returned by mmap().
>
> Only NX GZIP coprocessor type is supported right now and allow GZIP
> engine access via /dev/crypto/nx-gzip device node.
>
> Signed-off-by: Sukadev Bhattiprolu <[email-masked]>
> Signed-off-by: Haren Myneni <[email-masked]>
> ---
>  arch/powerpc/include/asm/vas.h              |  11 ++
>  arch/powerpc/platforms/powernv/Makefile     |   2 +-
>  arch/powerpc/platforms/powernv/vas-api.c    | 290 ++++++++++++++++++++++++++++
>  arch/powerpc/platforms/powernv/vas-window.c |   6 +-
>  arch/powerpc/platforms/powernv/vas.h        |   2 +
>  5 files changed, 307 insertions(+), 4 deletions(-)
>  create mode 100644 arch/powerpc/platforms/powernv/vas-api.c
>
> diff --git a/arch/powerpc/include/asm/vas.h b/arch/powerpc/include/asm/vas.h
> index f93e6b0..e064953 100644
> --- a/arch/powerpc/include/asm/vas.h
> +++ b/arch/powerpc/include/asm/vas.h
> @@ -163,4 +163,15 @@ struct vas_window *vas_tx_win_open(int vasid, enum vas_cop_type cop,
>   */
>  int vas_paste_crb(struct vas_window *win, int offset, bool re);
>  
> +/*
> + * Register / unregister coprocessor type to VAS API which will be exported
> + * to user space. Applications can use this API to open / close window
> + * which can be used to send / receive requests directly to cooprcessor.
> + *
> + * Only NX GZIP coprocessor type is supported now, but this API can be
> + * used for others in future.
> + */
> +int vas_register_coproc_api(struct module *mod);
> +void vas_unregister_coproc_api(void);
> +
>  #endif /* __ASM_POWERPC_VAS_H */
> diff --git a/arch/powerpc/platforms/powernv/Makefile b/arch/powerpc/platforms/powernv/Makefile
> index 395789f..fe3f0fb 100644
> --- a/arch/powerpc/platforms/powernv/Makefile
> +++ b/arch/powerpc/platforms/powernv/Makefile
> @@ -17,7 +17,7 @@ obj-$(CONFIG_MEMORY_FAILURE)	+= opal-memory-errors.o
>  obj-$(CONFIG_OPAL_PRD)	+= opal-prd.o
>  obj-$(CONFIG_PERF_EVENTS) += opal-imc.o
>  obj-$(CONFIG_PPC_MEMTRACE)	+= memtrace.o
> -obj-$(CONFIG_PPC_VAS)	+= vas.o vas-window.o vas-debug.o vas-fault.o
> +obj-$(CONFIG_PPC_VAS)	+= vas.o vas-window.o vas-debug.o vas-fault.o vas-api.o
>  obj-$(CONFIG_OCXL_BASE)	+= ocxl.o
>  obj-$(CONFIG_SCOM_DEBUGFS) += opal-xscom.o
>  obj-$(CONFIG_PPC_SECURE_BOOT) += opal-secvar.o
> diff --git a/arch/powerpc/platforms/powernv/vas-api.c b/arch/powerpc/platforms/powernv/vas-api.c
> new file mode 100644
> index 0000000..3473a4a
> --- /dev/null
> +++ b/arch/powerpc/platforms/powernv/vas-api.c
> @@ -0,0 +1,290 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * VAS user space API for its accelerators (Only NX-GZIP is supported now)
> + * Copyright (C) 2019 Haren Myneni, IBM Corp
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/device.h>
> +#include <linux/cdev.h>
> +#include <linux/fs.h>
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>
> +#include <asm/vas.h>
> +#include <uapi/asm/vas-api.h>
> +#include "vas.h"
> +
> +/*
> + * The driver creates the device node that can be used as follows:
> + * For NX-GZIP
> + *
> + *	fd = open("/dev/crypto/nx-gzip", O_RDWR);
> + *	rc = ioctl(fd, VAS_TX_WIN_OPEN, &attr);
> + *	paste_addr = mmap(NULL, PAGE_SIZE, prot, MAP_SHARED, fd, 0ULL).
> + *	vas_copy(&crb, 0, 1);
> + *	vas_paste(paste_addr, 0, 1);
> + *	close(fd) or exit process to close window.
> + *
> + * where "vas_copy" and "vas_paste" are defined in copy-paste.h.
> + * copy/paste returns to the user space directly. So refer NX hardware
> + * documententation for excat copy/paste usage and completion / error

s/excat/exact/

I'm still experimenting with this so I might have more comments later,
but I wanted to send this before I forgot or lost it :)

Daniel

> + * conditions.
> + */
> +
> +static char	*coproc_dev_name = "nx-gzip";
> +static atomic_t	coproc_instid = ATOMIC_INIT(0);
> +
> +/*
> + * Wrapper object for the nx-gzip device - there is just one instance of
> + * this node for the whole system.
> + */
> +static struct coproc_dev {
> +	struct cdev cdev;
> +	struct device *device;
> +	char *name;
> +	dev_t devt;
> +	struct class *class;
> +} coproc_device;
> +
> +/*
> + * One instance per open of a nx-gzip device. Each coproc_instance is
> + * associated with a VAS window after the caller issues
> + * VAS_GZIP_TX_WIN_OPEN ioctl.
> + */
> +struct coproc_instance {
> +	int id;
> +	struct vas_window *txwin;
> +};
> +
> +static char *coproc_devnode(struct device *dev, umode_t *mode)
> +{
> +	return kasprintf(GFP_KERNEL, "crypto/%s", dev_name(dev));
> +}
> +
> +static int coproc_open(struct inode *inode, struct file *fp)
> +{
> +	struct coproc_instance *instance;
> +
> +	instance = kzalloc(sizeof(*instance), GFP_KERNEL);
> +	if (!instance)
> +		return -ENOMEM;
> +
> +	instance->id = atomic_inc_return(&coproc_instid);
> +
> +	fp->private_data = instance;
> +	return 0;
> +}
> +
> +static int coproc_ioc_tx_win_open(struct file *fp, unsigned long arg)
> +{
> +	int rc, vasid;
> +	struct vas_tx_win_attr txattr;
> +	struct vas_tx_win_open_attr uattr;
> +	void __user *uptr = (void __user *)arg;
> +	struct vas_window *txwin;
> +	struct coproc_instance *nxti = fp->private_data;
> +
> +	if (!nxti)
> +		return -EINVAL;
> +
> +	/*
> +	 * One window for file descriptor
> +	 */
> +	if (nxti->txwin)
> +		return -EEXIST;
> +
> +	rc = copy_from_user(&uattr, uptr, sizeof(uattr));
> +	if (rc) {
> +		pr_err("%s(): copy_from_user() returns %d\n", __func__, rc);
> +		return -EFAULT;
> +	}
> +
> +	if (uattr.version != 1) {
> +		pr_err("Invalid version\n");
> +		return -EINVAL;
> +	}
> +
> +	vasid = uattr.vas_id;
> +
> +	memset(&txattr, 0, sizeof(struct vas_tx_win_attr));
> +	vas_init_tx_win_attr(&txattr, VAS_COP_TYPE_GZIP);
> +
> +	txattr.lpid = mfspr(SPRN_LPID);
> +	txattr.pidr = mfspr(SPRN_PID);
> +	txattr.user_win = true;
> +	txattr.rsvd_txbuf_count = false;
> +	txattr.pswid = false;
> +	/*
> +	 * txattr.wcreds_max is set to VAS_WCREDS_DEFAULT (1024) in
> +	 * vas-window.c, but can be changed specific to GZIP depends
> +	 * on user space need.
> +	 * If needed to set txattr.wcreds_max here.
> +	 */
> +
> +	pr_devel("Pid %d: Opening txwin, PIDR %ld\n", txattr.pidr,
> +				mfspr(SPRN_PID));
> +
> +	txwin = vas_tx_win_open(vasid, VAS_COP_TYPE_GZIP, &txattr);
> +	if (IS_ERR(txwin)) {
> +		pr_err("%s() vas_tx_win_open() failed, %ld\n", __func__,
> +					PTR_ERR(txwin));
> +		return PTR_ERR(txwin);
> +	}
> +
> +	nxti->txwin = txwin;
> +
> +	return 0;
> +}
> +
> +static int coproc_release(struct inode *inode, struct file *fp)
> +{
> +	struct coproc_instance *instance;
> +
> +	instance = fp->private_data;
> +
> +	if (instance && instance->txwin) {
> +		vas_win_close(instance->txwin);
> +		instance->txwin = NULL;
> +	}
> +
> +	/*
> +	 * We don't know here if user has other receive windows
> +	 * open, so we can't really call clear_thread_tidr().
> +	 * So, once the process calls set_thread_tidr(), the
> +	 * TIDR value sticks around until process exits, resulting
> +	 * in an extra copy in restore_sprs().
> +	 */
> +
> +	kfree(instance);
> +	fp->private_data = NULL;
> +	atomic_dec(&coproc_instid);
> +
> +	return 0;
> +}
> +
> +static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
> +{
> +	int rc;
> +	pgprot_t prot;
> +	u64 paste_addr;
> +	unsigned long pfn;
> +	struct coproc_instance *instance = fp->private_data;
> +
> +	if ((vma->vm_end - vma->vm_start) > PAGE_SIZE) {
> +		pr_debug("%s(): size 0x%zx, PAGE_SIZE 0x%zx\n", __func__,
> +				(vma->vm_end - vma->vm_start), PAGE_SIZE);
> +		return -EINVAL;
> +	}
> +
> +	/* Ensure instance has an open send window */
> +	if (!instance->txwin) {
> +		pr_err("%s(): No send window open?\n", __func__);
> +		return -EINVAL;
> +	}
> +
> +	vas_win_paste_addr(instance->txwin, &paste_addr, NULL);
> +	pfn = paste_addr >> PAGE_SHIFT;
> +
> +	/* flags, page_prot from cxl_mmap(), except we want cachable */
> +	vma->vm_flags |= VM_IO | VM_PFNMAP;
> +	vma->vm_page_prot = pgprot_cached(vma->vm_page_prot);
> +
> +	prot = __pgprot(pgprot_val(vma->vm_page_prot) | _PAGE_DIRTY);
> +
> +	rc = remap_pfn_range(vma, vma->vm_start, pfn + vma->vm_pgoff,
> +			vma->vm_end - vma->vm_start, prot);
> +
> +	pr_devel("%s(): paste addr %llx at %lx, rc %d\n", __func__,
> +			paste_addr, vma->vm_start, rc);
> +
> +	return rc;
> +}
> +
> +static long coproc_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
> +{
> +	switch (cmd) {
> +	case VAS_TX_WIN_OPEN:
> +		return coproc_ioc_tx_win_open(fp, arg);
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static struct file_operations coproc_fops = {
> +	.open = coproc_open,
> +	.release = coproc_release,
> +	.mmap = coproc_mmap,
> +	.unlocked_ioctl = coproc_ioctl,
> +};
> +
> +/*
> + * Supporting only nx-gzip coprocessor type now, but this API code
> + * extended to other coprocessor types later.
> + */
> +int vas_register_coproc_api(struct module *mod)
> +{
> +	int rc = -EINVAL;
> +	dev_t devno;
> +
> +	rc = alloc_chrdev_region(&coproc_device.devt, 1, 1, "nx-gzip");
> +	if (rc) {
> +		pr_err("Unable to allocate coproc major number: %i\n", rc);
> +		return rc;
> +	}
> +
> +	pr_devel("NX-GZIP device allocated, dev [%i,%i]\n",
> +			MAJOR(coproc_device.devt), MINOR(coproc_device.devt));
> +
> +	coproc_device.class = class_create(mod, "nx-gzip");
> +	if (IS_ERR(coproc_device.class)) {
> +		rc = PTR_ERR(coproc_device.class);
> +		pr_err("Unable to create NX-GZIP class %d\n", rc);
> +		goto err_class;
> +	}
> +	coproc_device.class->devnode = coproc_devnode;
> +
> +	coproc_fops.owner = mod;
> +	cdev_init(&coproc_device.cdev, &coproc_fops);
> +
> +	devno = MKDEV(MAJOR(coproc_device.devt), 0);
> +	rc = cdev_add(&coproc_device.cdev, devno, 1);
> +	if (rc) {
> +		pr_err("cdev_add() failed %d\n", rc);
> +		goto err_cdev;
> +	}
> +
> +	coproc_device.device = device_create(coproc_device.class, NULL,
> +			devno, NULL, coproc_dev_name, MINOR(devno));
> +	if (IS_ERR(coproc_device.device)) {
> +		rc = PTR_ERR(coproc_device.device);
> +		pr_err("Unable to create coproc-%d %d\n", MINOR(devno), rc);
> +		goto err;
> +	}
> +
> +	pr_devel("%s: Added dev [%d,%d]\n", __func__, MAJOR(devno),
> +			MINOR(devno));
> +
> +	return 0;
> +
> +err:
> +	cdev_del(&coproc_device.cdev);
> +err_cdev:
> +	class_destroy(coproc_device.class);
> +err_class:
> +	unregister_chrdev_region(coproc_device.devt, 1);
> +	return rc;
> +}
> +EXPORT_SYMBOL_GPL(vas_register_coproc_api);
> +
> +void vas_unregister_coproc_api(void)
> +{
> +	dev_t devno;
> +
> +	cdev_del(&coproc_device.cdev);
> +	devno = MKDEV(MAJOR(coproc_device.devt), 0);
> +	device_destroy(coproc_device.class, devno);
> +
> +	class_destroy(coproc_device.class);
> +	unregister_chrdev_region(coproc_device.devt, 1);
> +}
> +EXPORT_SYMBOL_GPL(vas_unregister_coproc_api);
> diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c
> index e9ab851..7484296 100644
> --- a/arch/powerpc/platforms/powernv/vas-window.c
> +++ b/arch/powerpc/platforms/powernv/vas-window.c
> @@ -26,7 +26,7 @@
>   * Compute the paste address region for the window @window using the
>   * ->paste_base_addr and ->paste_win_id_shift we got from device tree.
>   */
> -static void compute_paste_address(struct vas_window *window, u64 *addr, int *len)
> +void vas_win_paste_addr(struct vas_window *window, u64 *addr, int *len)
>  {
>  	int winid;
>  	u64 base, shift;
> @@ -80,7 +80,7 @@ static void *map_paste_region(struct vas_window *txwin)
>  		goto free_name;
>  
>  	txwin->paste_addr_name = name;
> -	compute_paste_address(txwin, &start, &len);
> +	vas_win_paste_addr(txwin, &start, &len);
>  
>  	if (!request_mem_region(start, len, name)) {
>  		pr_devel("%s(): request_mem_region(0x%llx, %d) failed\n",
> @@ -138,7 +138,7 @@ static void unmap_paste_region(struct vas_window *window)
>  	u64 busaddr_start;
>  
>  	if (window->paste_kaddr) {
> -		compute_paste_address(window, &busaddr_start, &len);
> +		vas_win_paste_addr(window, &busaddr_start, &len);
>  		unmap_region(window->paste_kaddr, busaddr_start, len);
>  		window->paste_kaddr = NULL;
>  		kfree(window->paste_addr_name);
> diff --git a/arch/powerpc/platforms/powernv/vas.h b/arch/powerpc/platforms/powernv/vas.h
> index 8c39a7d..a10abed 100644
> --- a/arch/powerpc/platforms/powernv/vas.h
> +++ b/arch/powerpc/platforms/powernv/vas.h
> @@ -431,6 +431,8 @@ struct vas_winctx {
>  extern void vas_return_credit(struct vas_window *window, bool tx);
>  extern struct vas_window *vas_pswid_to_window(struct vas_instance *vinst,
>  						uint32_t pswid);
> +extern void vas_win_paste_addr(struct vas_window *window, u64 *addr,
> +					int *len);
>  
>  static inline int vas_window_pid(struct vas_window *window)
>  {
> -- 
> 1.8.3.1