/*
* SPDX-License-Identifier: MIT
*
* Copyright © 2014-2016 Intel Corporation
*/
#include <linux/mman.h>
#include <linux/sizes.h>
#include "i915_drv.h"
#include "i915_gem_gtt.h"
#include "i915_gem_ioctls.h"
#include "i915_gem_object.h"
#include "i915_vma.h"
#include "intel_drv.h"
static inline bool
__vma_matches(struct vm_area_struct *vma, struct file *filp,
unsigned long addr, unsigned long size)
{
if (vma->vm_file != filp)
return false;
return vma->vm_start == addr &&
(vma->vm_end - vma->vm_start) == PAGE_ALIGN(size);
}
/**
* i915_gem_mmap_ioctl - Maps the contents of an object, returning the address
* it is mapped to.
* @dev: drm device
* @data: ioctl data blob
* @file: drm file
*
* While the mapping holds a reference on the contents of the object, it doesn't
* imply a ref on the object itself.
*
* IMPORTANT:
*
* DRM driver writers who look a this function as an example for how to do GEM
* mmap support, please don't implement mmap support like here. The modern way
* to implement DRM mmap support is with an mmap offset ioctl (like
* i915_gem_mmap_gtt) and then using the mmap syscall on the DRM fd directly.
* That way debug tooling like valgrind will understand what's going on, hiding
* the mmap call in a driver private ioctl will break that. The i915 driver only
* does cpu mmaps this way because we didn't know better.
*/
int
i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
struct drm_file *file)
{
struct drm_i915_gem_mmap *args = data;
struct drm_i915_gem_object *obj;
unsigned long addr;
if (args->flags & ~(I915_MMAP_WC))
return -EINVAL;
if (args->flags & I915_MMAP_WC && !boot_cpu_has(X86_FEATURE_PAT))
return -ENODEV;
obj = i915_gem_object_lookup(file, args->handle);
if (!obj)
return -ENOENT;
/* prime objects have no backing filp to GEM mmap
* pages from.
*/
if (!obj->base.filp) {
addr = -ENXIO;
goto err;
}
if (range_overflows(args->offset, args->size, (u64)obj->base.size)) {
addr = -EINVAL;
goto err;
}
addr = vm_mmap(obj->base.filp, 0, args->size,
PROT_READ | PROT_WRITE, MAP_SHARED,
args->offset);
if (IS_ERR_VALUE(addr))
goto err;
if (args->flags & I915_MMAP_WC) {
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
if (down_write_killable(&mm->mmap_sem)) {
addr = -EINTR;
goto err;
}
vma = find_vma(mm, addr);
if (vma && __vma_matches(vma, obj->base.filp, addr, args->size))
vma->vm_page_prot =
pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
else
addr = -ENOMEM;
up_write(&mm->mmap_sem);
if (IS_ERR_VALUE(addr))
goto err;
/* This may race, but that's ok, it only gets set */
WRITE_ONCE(obj->frontbuffer_ggtt_origin, ORIGIN_CPU);
}
i915_gem_object_put(obj);
args->addr_ptr = (u64)addr;
return 0;
err:
i915_gem_object_put(obj);
return addr;
}
static unsigned int tile_row_pages(const struct drm_i915_gem_object *obj)
{
return i915_gem_object_get_tile_row_size(obj) >> PAGE_SHIFT;
}
/**
* i915_gem_mmap_gtt_version - report the current feature set for GTT mmaps
*
* A history of the GTT mmap interface:
*
* 0 - Everything had to fit into the GTT. Both parties of a memcpy had to
* aligned and suitable for fencing, and still fit into the available
* mappable space left by the pinned display objects. A classic problem
* we called the page-fault-of-doom where we would ping-pong between
* two objects that could not fit inside the GTT and so the memcpy
* would page one object in at the expense of the other between every
* single byte.
*
* 1 - Objects can be any size, and have any compatible fencing (X Y, or none
* as set via i915_gem_set_tiling() [DRM_I915_GEM_SET_TILING]). If the
* object is too large for the available space (or simply too large
* for the mappable aperture!), a view is created instead and faulted
* into userspace. (This view is aligned and sized appropriately for
* fenced access.)
*
* 2 - Recognise WC as a separate cache domain so that we can flush the
* delayed writes via GTT before performing direct access via WC.
*
* 3 - Remove implicit set-domain(GTT) and synchronisation on initial
* pagefault; swapin remains transparent.
*
* Restrictions:
*
* * snoopable objects cannot be accessed via the GTT. It can cause machine
* hangs on some architectures, corruption on others. An attempt to service
* a GTT page fault from a snoopable object will generate a SIGBUS.
*
* * the object must be able to fit into RAM (physical memory, though no
* limited to the mappable aperture).
*
*
* Caveats:
*
* * a new GTT page fault will synchronize rendering from the GPU and flush
* all data to system memory. Subsequent access will not be synchronized.
*
* * all mappings are revoked on runtime device suspend.
*
* * there are only 8, 16 or 32 fence registers to share between all users
* (older machines require fence register for display and blitter access
* as well). Contention of the fence registers will cause the previous users
* to be unmapped and any new access will generate new page faults.
*
* * running out of memory while servicing a fault may generate a SIGBUS,
* rather than the expected SIGSEGV.
*/
int i915_gem_mmap_gtt_version(void)
{
return 3;
}
static inline struct i915_ggtt_view
compute_partial_view(const struct drm_i915_gem_object *obj,
pgoff_t page_offset,
unsigned int chunk)
{
struct i915_ggtt_view view;
if (i915_gem_object_is_tiled(obj))
chunk = roundup(chunk, tile_row_pages(obj));
view.type = I915_GGTT_VIEW_PARTIAL;
view.partial.offset = rounddown(page_offset, chunk);
view.partial.size =
min_t(unsigned int, chunk,
(obj->base.size >> PAGE_SHIFT) - view.partial.offset);
/* If the partial covers the entire object, just create a normal VMA. */
if (chunk >= obj->base.size >> PAGE_SHIFT)
view.type = I915_GGTT_VIEW_NORMAL;
return view;
}
/**
* i915_gem_fault - fault a page into the GTT
* @vmf: fault info
*
* The fault handler is set up by drm_gem_mmap() when a object is GTT mapped
* from userspace. The fault handler takes care of binding the object to
* the GTT (if needed), allocating and programming a fence register (again,
* only if needed based on whether the old reg is still valid or the object
* is tiled) and inserting a new PTE into the faulting process.
*
* Note that the faulting process may involve evicting existing objects
* from the GTT and/or fence registers to make room. So performance may
* suffer if the GTT working set is large or there are few fence registers
* left.
*
* The current feature set supported by i915_gem_fault() and thus GTT mmaps
* is exposed via I915_PARAM_MMAP_GTT_VERSION (see i915_gem_mmap_gtt_version).
*/
vm_fault_t i915_gem_fault(struct vm_fault *vmf)
{
#define MIN_CHUNK_PAGES (SZ_1M >> PAGE_SHIFT)
struct vm_area_struct *area = vmf->vma;
struct drm_i915_gem_object *obj = to_intel_bo(area->vm_private_data);
struct drm_device *dev = obj->base.dev;
struct drm_i915_private *i915 = to_i915(dev);
struct intel_runtime_pm *rpm = &i915->runtime_pm;
struct i915_ggtt *ggtt = &i915->ggtt;
bool write = area->vm_flags & VM_WRITE;
intel_wakeref_t wakeref;
struct i915_vma *vma;
pgoff_t page_offset;
int srcu;
int ret;
/* Sanity check that we allow writing into this object */
if (i915_gem_object_is_readonly(obj) && write)
return VM_FAULT_SIGBUS;
/* We don't use vmf->pgoff since that has the fake offset */
page_offset = (vmf->address - area->vm_start) >> PAGE_SHIFT;
trace_i915_gem_object_fault(obj, page_offset, true, write);
ret = i915_gem_object_pin_pages(obj);
if (ret)
goto err;
wakeref = intel_runtime_pm_get(rpm);
srcu = i915_reset_trylock(i915);
if (srcu < 0) {
ret = srcu;
goto err_rpm;
}
ret = i915_mutex_lock_interruptible(dev);
if (ret)
goto err_reset;
/* Access to snoopable pages through the GTT is incoherent. */
if (obj->cache_level != I915_CACHE_NONE && !HAS_LLC(i915)) {
ret = -EFAULT;
goto err_unlock;
}
/* Now pin it into the GTT as needed */
vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0,
PIN_MAPPABLE |
PIN_NONBLOCK |
PIN_NONFAULT);
if (IS_ERR(vma)) {
/* Use a partial view if it is bigger than available space */
struct i915_ggtt_view view =
compute_partial_view(obj, page_offset, MIN_CHUNK_PAGES);
unsigned int flags;
flags = PIN_MAPPABLE;
if (view.type == I915_GGTT_VIEW_NORMAL)
flags |= PIN_NONBLOCK; /* avoid warnings for pinned */
/*
* Userspace is now writing through an untracked VMA, abandon
* all hope that the hardware is able to track future writes.
*/
obj->frontbuffer_ggtt_origin = ORIGIN_CPU;
vma = i915_gem_object_ggtt_pin(obj, &view, 0, 0, flags);
if (IS_ERR(vma) && !view.type) {
flags = PIN_MAPPABLE;
view.type = I915_GGTT_VIEW_PARTIAL;
vma = i915_gem_object_ggtt_pin(obj, &view, 0, 0, flags);
}
}
if (IS_ERR(vma)) {
ret = PTR_ERR(vma);
goto err_unlock;
}
ret = i915_vma_pin_fence(vma);
if (ret)
goto err_unpin;
/* Finally, remap it using the new GTT offset */
ret = remap_io_mapping(area,
area->vm_start + (vma->ggtt_view.partial.offset << PAGE_SHIFT),
(ggtt->gmadr.start + vma->node.start) >> PAGE_SHIFT,
min_t(u64, vma->size, area->vm_end - area->vm_start),
&ggtt->iomap);
if (ret)
goto err_fence;
/* Mark as being mmapped into userspace for later revocation */
assert_rpm_wakelock_held(rpm);
if (!i915_vma_set_userfault(vma) && !obj->userfault_count++)
list_add(&obj->userfault_link, &i915->ggtt.userfault_list);
if (CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND)
intel_wakeref_auto(&i915->ggtt.userfault_wakeref,
msecs_to_jiffies_timeout(CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND));
GEM_BUG_ON(!obj->userfault_count);
i915_vma_set_ggtt_write(vma);
err_fence:
i915_vma_unpin_fence(vma);
err_unpin:
__i915_vma_unpin(vma);
err_unlock:
mutex_unlock(&dev->struct_mutex);
err_reset:
i915_reset_unlock(i915, srcu);
err_rpm:
intel_runtime_pm_put(rpm, wakeref);
i915_gem_object_unpin_pages(obj);
err:
switch (ret) {
case -EIO:
/*
* We eat errors when the gpu is terminally wedged to avoid
* userspace unduly crashing (gl has no provisions for mmaps to
* fail). But any other -EIO isn't ours (e.g. swap in failure)
* and so needs to be reported.
*/
if (!i915_terminally_wedged(i915))
return VM_FAULT_SIGBUS;
/* else, fall through */
case -EAGAIN:
/*
* EAGAIN means the gpu is hung and we'll wait for the error
* handler to reset everything when re-faulting in
* i915_mutex_lock_interruptible.
*/
case 0:
case -ERESTARTSYS:
case -EINTR:
case -EBUSY:
/*
* EBUSY is ok: this just means that another thread
* already did the job.
*/
return VM_FAULT_NOPAGE;
case -ENOMEM:
return VM_FAULT_OOM;
case -ENOSPC:
case -EFAULT:
return VM_FAULT_SIGBUS;
default:
WARN_ONCE(ret, "unhandled error in %s: %i\n", __func__, ret);
return VM_FAULT_SIGBUS;
}
}
void __i915_gem_object_release_mmap(struct drm_i915_gem_object *obj)
{
struct i915_vma *vma;
GEM_BUG_ON(!obj->userfault_count);
obj->userfault_count = 0;
list_del(&obj->userfault_link);
drm_vma_node_unmap(&obj->base.vma_node,
obj->base.dev->anon_inode->i_mapping);
for_each_ggtt_vma(vma, obj)
i915_vma_unset_userfault(vma);
}
/**
* i915_gem_object_release_mmap - remove physical page mappings
* @obj: obj in question
*
* Preserve the reservation of the mmapping with the DRM core code, but
* relinquish ownership of the pages back to the system.
*
* It is vital that we remove the page mapping if we have mapped a tiled
* object through the GTT and then lose the fence register due to
* resource pressure. Similarly if the object has been moved out of the
* aperture, than pages mapped into userspace must be revoked. Removing the
* mapping will then trigger a page fault on the next user access, allowing
* fixup by i915_gem_fault().
*/
void i915_gem_object_release_mmap(struct drm_i915_gem_object *obj)
{
struct drm_i915_private *i915 = to_i915(obj->base.dev);
intel_wakeref_t wakeref;
/* Serialisation between user GTT access and our code depends upon
* revoking the CPU's PTE whilst the mutex is held. The next user
* pagefault then has to wait until we release the mutex.
*
* Note that RPM complicates somewhat by adding an additional
* requirement that operations to the GGTT be made holding the RPM
* wakeref.
*/
lockdep_assert_held(&i915->drm.struct_mutex);
wakeref = intel_runtime_pm_get(&i915->runtime_pm);
if (!obj->userfault_count)
goto out;
__i915_gem_object_release_mmap(obj);
/* Ensure that the CPU's PTE are revoked and there are not outstanding
* memory transactions from userspace before we return. The TLB
* flushing implied above by changing the PTE above *should* be
* sufficient, an extra barrier here just provides us with a bit
* of paranoid documentation about our requirement to serialise
* memory writes before touching registers / GSM.
*/
wmb();
out:
intel_runtime_pm_put(&i915->runtime_pm, wakeref);
}
static int create_mmap_offset(struct drm_i915_gem_object *obj)
{
struct drm_i915_private *i915 = to_i915(obj->base.dev);
int err;
err = drm_gem_create_mmap_offset(&obj->base);
if (likely(!err))
return 0;
/* Attempt to reap some mmap space from dead objects */
do {
err = i915_gem_wait_for_idle(i915,
I915_WAIT_INTERRUPTIBLE,
MAX_SCHEDULE_TIMEOUT);
if (err)
break;
i915_gem_drain_freed_objects(i915);
err = drm_gem_create_mmap_offset(&obj->base);
if (!err)
break;
} while (flush_delayed_work(&i915->gem.retire_work));
return err;
}
int
i915_gem_mmap_gtt(struct drm_file *file,
struct drm_device *dev,
u32 handle,
u64 *offset)
{
struct drm_i915_gem_object *obj;
int ret;
obj = i915_gem_object_lookup(file, handle);
if (!obj)
return -ENOENT;
ret = create_mmap_offset(obj);
if (ret == 0)
*offset = drm_vma_node_offset_addr(&obj->base.vma_node);
i915_gem_object_put(obj);
return ret;
}
/**
* i915_gem_mmap_gtt_ioctl - prepare an object for GTT mmap'ing
* @dev: DRM device
* @data: GTT mapping ioctl data
* @file: GEM object info
*
* Simply returns the fake offset to userspace so it can mmap it.
* The mmap call will end up in drm_gem_mmap(), which will set things
* up so we can get faults in the handler above.
*
* The fault handler will take care of binding the object into the GTT
* (since it may have been evicted to make room for something), allocating
* a fence register, and mapping the appropriate aperture address into
* userspace.
*/
int
i915_gem_mmap_gtt_ioctl(struct drm_device *dev, void *data,
struct drm_file *file)
{
struct drm_i915_gem_mmap_gtt *args = data;
return i915_gem_mmap_gtt(file, dev, args->handle, &args->offset);
}
#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftests/i915_gem_mman.c"
#endif
