// 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
*/
#define pr_fmt(fmt) "vas-api: " fmt
#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 <linux/kthread.h>
#include <linux/sched/signal.h>
#include <linux/mmu_context.h>
#include <linux/io.h>
#include <asm/vas.h>
#include <uapi/asm/vas-api.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
* documentation for exact copy/paste usage and completion / error
* conditions.
*/
/*
* 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;
enum vas_cop_type cop_type;
const struct vas_user_win_ops *vops;
} coproc_device;
struct coproc_instance {
struct coproc_dev *coproc;
struct vas_window *txwin;
};
static char *coproc_devnode(const struct device *dev, umode_t *mode)
{
return kasprintf(GFP_KERNEL, "crypto/%s", dev_name(dev));
}
/*
* Take reference to pid and mm
*/
int get_vas_user_win_ref(struct vas_user_win_ref *task_ref)
{
/*
* Window opened by a child thread may not be closed when
* it exits. So take reference to its pid and release it
* when the window is free by parent thread.
* Acquire a reference to the task's pid to make sure
* pid will not be re-used - needed only for multithread
* applications.
*/
task_ref->pid = get_task_pid(current, PIDTYPE_PID);
/*
* Acquire a reference to the task's mm.
*/
task_ref->mm = get_task_mm(current);
if (!task_ref->mm) {
put_pid(task_ref->pid);
pr_err("pid(%d): mm_struct is not found\n",
current->pid);
return -EPERM;
}
mmgrab(task_ref->mm);
mmput(task_ref->mm);
/*
* Process closes window during exit. In the case of
* multithread application, the child thread can open
* window and can exit without closing it. So takes tgid
* reference until window closed to make sure tgid is not
* reused.
*/
task_ref->tgid = find_get_pid(task_tgid_vnr(current));
return 0;
}
/*
* Successful return must release the task reference with
* put_task_struct
*/
static bool ref_get_pid_and_task(struct vas_user_win_ref *task_ref,
struct task_struct **tskp, struct pid **pidp)
{
struct task_struct *tsk;
struct pid *pid;
pid = task_ref->pid;
tsk = get_pid_task(pid, PIDTYPE_PID);
if (!tsk) {
pid = task_ref->tgid;
tsk = get_pid_task(pid, PIDTYPE_PID);
/*
* Parent thread (tgid) will be closing window when it
* exits. So should not get here.
*/
if (WARN_ON_ONCE(!tsk))
return false;
}
/* Return if the task is exiting. */
if (tsk->flags & PF_EXITING) {
put_task_struct(tsk);
return false;
}
*tskp = tsk;
*pidp = pid;
return true;
}
/*
* Update the CSB to indicate a translation error.
*
* User space will be polling on CSB after the request is issued.
* If NX can handle the request without any issues, it updates CSB.
* Whereas if NX encounters page fault, the kernel will handle the
* fault and update CSB with translation error.
*
* If we are unable to update the CSB means copy_to_user failed due to
* invalid csb_addr, send a signal to the process.
*/
void vas_update_csb(struct coprocessor_request_block *crb,
struct vas_user_win_ref *task_ref)
{
struct coprocessor_status_block csb;
struct kernel_siginfo info;
struct task_struct *tsk;
void __user *csb_addr;
struct pid *pid;
int rc;
/*
* NX user space windows can not be opened for task->mm=NULL
* and faults will not be generated for kernel requests.
*/
if (WARN_ON_ONCE(!task_ref->mm))
return;
csb_addr = (void __user *)be64_to_cpu(crb->csb_addr);
memset(&csb, 0, sizeof(csb));
csb.cc = CSB_CC_FAULT_ADDRESS;
csb.ce = CSB_CE_TERMINATION;
csb.cs = 0;
csb.count = 0;
/*
* NX operates and returns in BE format as defined CRB struct.
* So saves fault_storage_addr in BE as NX pastes in FIFO and
* expects user space to convert to CPU format.
*/
csb.address = crb->stamp.nx.fault_storage_addr;
csb.flags = 0;
/*
* Process closes send window after all pending NX requests are
* completed. In multi-thread applications, a child thread can
* open a window and can exit without closing it. May be some
* requests are pending or this window can be used by other
* threads later. We should handle faults if NX encounters
* pages faults on these requests. Update CSB with translation
* error and fault address. If csb_addr passed by user space is
* invalid, send SEGV signal to pid saved in window. If the
* child thread is not running, send the signal to tgid.
* Parent thread (tgid) will close this window upon its exit.
*
* pid and mm references are taken when window is opened by
* process (pid). So tgid is used only when child thread opens
* a window and exits without closing it.
*/
if (!ref_get_pid_and_task(task_ref, &tsk, &pid))
return;
kthread_use_mm(task_ref->mm);
rc = copy_to_user(csb_addr, &csb, sizeof(csb));
/*
* User space polls on csb.flags (first byte). So add barrier
* then copy first byte with csb flags update.
*/
if (!rc) {
csb.flags = CSB_V;
/* Make sure update to csb.flags is visible now */
smp_mb();
rc = copy_to_user(csb_addr, &csb, sizeof(u8));
}
kthread_unuse_mm(task_ref->mm);
put_task_struct(tsk);
/* Success */
if (!rc)
return;
pr_debug("Invalid CSB address 0x%p signalling pid(%d)\n",
csb_addr, pid_vnr(pid));
clear_siginfo(&info);
info.si_signo = SIGSEGV;
info.si_errno = EFAULT;
info.si_code = SEGV_MAPERR;
info.si_addr = csb_addr;
/*
* process will be polling on csb.flags after request is sent to
* NX. So generally CSB update should not fail except when an
* application passes invalid csb_addr. So an error message will
* be displayed and leave it to user space whether to ignore or
* handle this signal.
*/
rcu_read_lock();
rc = kill_pid_info(SIGSEGV, &info, pid);
rcu_read_unlock();
pr_devel("pid %d kill_proc_info() rc %d\n", pid_vnr(pid), rc);
}
void vas_dump_crb(struct coprocessor_request_block *crb)
{
struct data_descriptor_entry *dde;
struct nx_fault_stamp *nx;
dde = &crb->source;
pr_devel("SrcDDE: addr 0x%llx, len %d, count %d, idx %d, flags %d\n",
be64_to_cpu(dde->address), be32_to_cpu(dde->length),
dde->count, dde->index, dde->flags);
dde = &crb->target;
pr_devel("TgtDDE: addr 0x%llx, len %d, count %d, idx %d, flags %d\n",
be64_to_cpu(dde->address), be32_to_cpu(dde->length),
dde->count, dde->index, dde->flags);
nx = &crb->stamp.nx;
pr_devel("NX Stamp: PSWID 0x%x, FSA 0x%llx, flags 0x%x, FS 0x%x\n",
be32_to_cpu(nx->pswid),
be64_to_cpu(crb->stamp.nx.fault_storage_addr),
nx->flags, nx->fault_status);
}
static int coproc_open(struct inode *inode, struct file *fp)
{
struct coproc_instance *cp_inst;
cp_inst = kzalloc(sizeof(*cp_inst), GFP_KERNEL);
if (!cp_inst)
return -ENOMEM;
cp_inst->coproc = container_of(inode->i_cdev, struct coproc_dev,
cdev);
fp->private_data = cp_inst;
return 0;
}
static int coproc_ioc_tx_win_open(struct file *fp, unsigned long arg)
{
void __user *uptr = (void __user *)arg;
struct vas_tx_win_open_attr uattr;
struct coproc_instance *cp_inst;
struct vas_window *txwin;
int rc;
cp_inst = fp->private_data;
/*
* One window for file descriptor
*/
if (cp_inst->txwin)
return -EEXIST;
rc = copy_from_user(&uattr, uptr, sizeof(uattr));
if (rc) {
pr_err("copy_from_user() returns %d\n", rc);
return -EFAULT;
}
if (uattr.version != 1) {
pr_err("Invalid window open API version\n");
return -EINVAL;
}
if (!cp_inst->coproc->vops || !cp_inst->coproc->vops->open_win) {
pr_err("VAS API is not registered\n");
return -EACCES;
}
txwin = cp_inst->coproc->vops->open_win(uattr.vas_id, uattr.flags,
cp_inst->coproc->cop_type);
if (IS_ERR(txwin)) {
pr_err_ratelimited("VAS window open failed rc=%ld\n",
PTR_ERR(txwin));
return PTR_ERR(txwin);
}
mutex_init(&txwin->task_ref.mmap_mutex);
cp_inst->txwin = txwin;
return 0;
}
static int coproc_release(struct inode *inode, struct file *fp)
{
struct coproc_instance *cp_inst = fp->private_data;
int rc;
if (cp_inst->txwin) {
if (cp_inst->coproc->vops &&
cp_inst->coproc->vops->close_win) {
rc = cp_inst->coproc->vops->close_win(cp_inst->txwin);
if (rc)
return rc;
}
cp_inst->txwin = NULL;
}
kfree(cp_inst);
fp->private_data = 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().
*/
return 0;
}
/*
* If the executed instruction that caused the fault was a paste, then
* clear regs CR0[EQ], advance NIP, and return 0. Else return error code.
*/
static int do_fail_paste(void)
{
struct pt_regs *regs = current->thread.regs;
u32 instword;
if (WARN_ON_ONCE(!regs))
return -EINVAL;
if (WARN_ON_ONCE(!user_mode(regs)))
return -EINVAL;
/*
* If we couldn't translate the instruction, the driver should
* return success without handling the fault, it will be retried
* or the instruction fetch will fault.
*/
if (get_user(instword, (u32 __user *)(regs->nip)))
return -EAGAIN;
/*
* Not a paste instruction, driver may fail the fault.
*/
if ((instword & PPC_INST_PASTE_MASK) != PPC_INST_PASTE)
return -ENOENT;
regs->ccr &= ~0xe0000000; /* Clear CR0[0-2] to fail paste */
regs_add_return_ip(regs, 4); /* Emulate the paste */
return 0;
}
/*
* This fault handler is invoked when the core generates page fault on
* the paste address. Happens if the kernel closes window in hypervisor
* (on pseries) due to lost credit or the paste address is not mapped.
*/
static vm_fault_t vas_mmap_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct file *fp = vma->vm_file;
struct coproc_instance *cp_inst = fp->private_data;
struct vas_window *txwin;
vm_fault_t fault;
u64 paste_addr;
int ret;
/*
* window is not opened. Shouldn't expect this error.
*/
if (!cp_inst || !cp_inst->txwin) {
pr_err("Unexpected fault on paste address with TX window closed\n");
return VM_FAULT_SIGBUS;
}
txwin = cp_inst->txwin;
/*
* When the LPAR lost credits due to core removal or during
* migration, invalidate the existing mapping for the current
* paste addresses and set windows in-active (zap_vma_pages in
* reconfig_close_windows()).
* New mapping will be done later after migration or new credits
* available. So continue to receive faults if the user space
* issue NX request.
*/
if (txwin->task_ref.vma != vmf->vma) {
pr_err("No previous mapping with paste address\n");
return VM_FAULT_SIGBUS;
}
mutex_lock(&txwin->task_ref.mmap_mutex);
/*
* The window may be inactive due to lost credit (Ex: core
* removal with DLPAR). If the window is active again when
* the credit is available, map the new paste address at the
* window virtual address.
*/
if (txwin->status == VAS_WIN_ACTIVE) {
paste_addr = cp_inst->coproc->vops->paste_addr(txwin);
if (paste_addr) {
fault = vmf_insert_pfn(vma, vma->vm_start,
(paste_addr >> PAGE_SHIFT));
mutex_unlock(&txwin->task_ref.mmap_mutex);
return fault;
}
}
mutex_unlock(&txwin->task_ref.mmap_mutex);
/*
* Received this fault due to closing the actual window.
* It can happen during migration or lost credits.
* Since no mapping, return the paste instruction failure
* to the user space.
*/
ret = do_fail_paste();
/*
* The user space can retry several times until success (needed
* for migration) or should fallback to SW compression or
* manage with the existing open windows if available.
* Looking at sysfs interface, it can determine whether these
* failures are coming during migration or core removal:
* nr_used_credits > nr_total_credits when lost credits
*/
if (!ret || (ret == -EAGAIN))
return VM_FAULT_NOPAGE;
return VM_FAULT_SIGBUS;
}
static const struct vm_operations_struct vas_vm_ops = {
.fault = vas_mmap_fault,
};
static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
{
struct coproc_instance *cp_inst = fp->private_data;
struct vas_window *txwin;
unsigned long pfn;
u64 paste_addr;
pgprot_t prot;
int rc;
txwin = cp_inst->txwin;
if ((vma->vm_end - vma->vm_start) > PAGE_SIZE) {
pr_debug("size 0x%zx, PAGE_SIZE 0x%zx\n",
(vma->vm_end - vma->vm_start), PAGE_SIZE);
return -EINVAL;
}
/* Ensure instance has an open send window */
if (!txwin) {
pr_err("No send window open?\n");
return -EINVAL;
}
if (!cp_inst->coproc->vops || !cp_inst->coproc->vops->paste_addr) {
pr_err("VAS API is not registered\n");
return -EACCES;
}
/*
* The initial mmap is done after the window is opened
* with ioctl. But before mmap(), this window can be closed in
* the hypervisor due to lost credit (core removal on pseries).
* So if the window is not active, return mmap() failure with
* -EACCES and expects the user space reissue mmap() when it
* is active again or open new window when the credit is available.
* mmap_mutex protects the paste address mmap() with DLPAR
* close/open event and allows mmap() only when the window is
* active.
*/
mutex_lock(&txwin->task_ref.mmap_mutex);
if (txwin->status != VAS_WIN_ACTIVE) {
pr_err("Window is not active\n");
rc = -EACCES;
goto out;
}
paste_addr = cp_inst->coproc->vops->paste_addr(txwin);
if (!paste_addr) {
pr_err("Window paste address failed\n");
rc = -EINVAL;
goto out;
}
pfn = paste_addr >> PAGE_SHIFT;
/* flags, page_prot from cxl_mmap(), except we want cachable */
vm_flags_set(vma, 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("paste addr %llx at %lx, rc %d\n", paste_addr,
vma->vm_start, rc);
txwin->task_ref.vma = vma;
vma->vm_ops = &vas_vm_ops;
out:
mutex_unlock(&txwin->task_ref.mmap_mutex);
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, enum vas_cop_type cop_type,
const char *name,
const struct vas_user_win_ops *vops)
{
int rc = -EINVAL;
dev_t devno;
rc = alloc_chrdev_region(&coproc_device.devt, 1, 1, name);
if (rc) {
pr_err("Unable to allocate coproc major number: %i\n", rc);
return rc;
}
pr_devel("%s device allocated, dev [%i,%i]\n", name,
MAJOR(coproc_device.devt), MINOR(coproc_device.devt));
coproc_device.class = class_create(name);
if (IS_ERR(coproc_device.class)) {
rc = PTR_ERR(coproc_device.class);
pr_err("Unable to create %s class %d\n", name, rc);
goto err_class;
}
coproc_device.class->devnode = coproc_devnode;
coproc_device.cop_type = cop_type;
coproc_device.vops = vops;
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, 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("Added dev [%d,%d]\n", 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;
}
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);
}
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