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HMM patches for 5.3-rc

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Fix the locking around nouveau's use of the hmm_range_* APIs. It works
 correctly in the success case, but many of the the edge cases have missing
 unlocks or double unlocks.
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Merge tag 'for-linus-hmm' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma

Pull HMM fixes from Jason Gunthorpe:
 "Fix the locking around nouveau's use of the hmm_range_* APIs. It works
  correctly in the success case, but many of the the edge cases have
  missing unlocks or double unlocks.

  The diffstat is a bit big as Christoph did a comprehensive job to move
  the obsolete API from the core header and into the driver before
  fixing its flow, but the risk of regression from this code motion is
  low"

* tag 'for-linus-hmm' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma:
  nouveau: unlock mmap_sem on all errors from nouveau_range_fault
  nouveau: remove the block parameter to nouveau_range_fault
  mm/hmm: move hmm_vma_range_done and hmm_vma_fault to nouveau
  mm/hmm: always return EBUSY for invalid ranges in hmm_range_{fault,snapshot}
This commit is contained in:
Linus Torvalds 2019-07-30 12:54:44 -07:00
commit 515f12b9ee
4 changed files with 49 additions and 64 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/vm/hmm.rst
View File

@ -237,7 +237,7 @@ The usage pattern is::
ret = hmm_range_snapshot(&range);
if (ret) {
up_read(&mm->mmap_sem);
if (ret == -EAGAIN) {
if (ret == -EBUSY) {
/*
* No need to check hmm_range_wait_until_valid() return value
* on retry we will get proper error with hmm_range_snapshot()

47
drivers/gpu/drm/nouveau/nouveau_svm.c
View File

@ -475,6 +475,47 @@ nouveau_svm_fault_cache(struct nouveau_svm *svm,
fault->inst, fault->addr, fault->access);
}
static inline bool
nouveau_range_done(struct hmm_range *range)
{
bool ret = hmm_range_valid(range);
hmm_range_unregister(range);
return ret;
}
static int
nouveau_range_fault(struct hmm_mirror *mirror, struct hmm_range *range)
{
long ret;
range->default_flags = 0;
range->pfn_flags_mask = -1UL;
ret = hmm_range_register(range, mirror,
range->start, range->end,
PAGE_SHIFT);
if (ret) {
up_read(&range->vma->vm_mm->mmap_sem);
return (int)ret;
}
if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) {
up_read(&range->vma->vm_mm->mmap_sem);
return -EAGAIN;
}
ret = hmm_range_fault(range, true);
if (ret <= 0) {
if (ret == 0)
ret = -EBUSY;
up_read(&range->vma->vm_mm->mmap_sem);
hmm_range_unregister(range);
return ret;
}
return 0;
}
static int
nouveau_svm_fault(struct nvif_notify *notify)
{
@ -649,10 +690,10 @@ nouveau_svm_fault(struct nvif_notify *notify)
range.values = nouveau_svm_pfn_values;
range.pfn_shift = NVIF_VMM_PFNMAP_V0_ADDR_SHIFT;
again:
ret = hmm_vma_fault(&svmm->mirror, &range, true);
ret = nouveau_range_fault(&svmm->mirror, &range);
if (ret == 0) {
mutex_lock(&svmm->mutex);
if (!hmm_vma_range_done(&range)) {
if (!nouveau_range_done(&range)) {
mutex_unlock(&svmm->mutex);
goto again;
}
@ -666,8 +707,8 @@ again:
NULL);
svmm->vmm->vmm.object.client->super = false;
mutex_unlock(&svmm->mutex);
up_read(&svmm->mm->mmap_sem);
}
up_read(&svmm->mm->mmap_sem);
/* Cancel any faults in the window whose pages didn't manage
* to keep their valid bit, or stay writeable when required.

54
include/linux/hmm.h
View File

@ -484,60 +484,6 @@ long hmm_range_dma_unmap(struct hmm_range *range,
*/
#define HMM_RANGE_DEFAULT_TIMEOUT 1000
/* This is a temporary helper to avoid merge conflict between trees. */
static inline bool hmm_vma_range_done(struct hmm_range *range)
{
bool ret = hmm_range_valid(range);
hmm_range_unregister(range);
return ret;
}
/* This is a temporary helper to avoid merge conflict between trees. */
static inline int hmm_vma_fault(struct hmm_mirror *mirror,
struct hmm_range *range, bool block)
{
long ret;
/*
* With the old API the driver must set each individual entries with
* the requested flags (valid, write, ...). So here we set the mask to
* keep intact the entries provided by the driver and zero out the
* default_flags.
*/
range->default_flags = 0;
range->pfn_flags_mask = -1UL;
ret = hmm_range_register(range, mirror,
range->start, range->end,
PAGE_SHIFT);
if (ret)
return (int)ret;
if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) {
/*
* The mmap_sem was taken by driver we release it here and
* returns -EAGAIN which correspond to mmap_sem have been
* drop in the old API.
*/
up_read(&range->vma->vm_mm->mmap_sem);
return -EAGAIN;
}
ret = hmm_range_fault(range, block);
if (ret <= 0) {
if (ret == -EBUSY || !ret) {
/* Same as above, drop mmap_sem to match old API. */
up_read(&range->vma->vm_mm->mmap_sem);
ret = -EBUSY;
} else if (ret == -EAGAIN)
ret = -EBUSY;
hmm_range_unregister(range);
return ret;
}
return 0;
}
/* Below are for HMM internal use only! Not to be used by device driver! */
static inline void hmm_mm_init(struct mm_struct *mm)
{

10
mm/hmm.c
View File

@ -946,7 +946,7 @@ EXPORT_SYMBOL(hmm_range_unregister);
* @range: range
* Return: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
* permission (for instance asking for write and range is read only),
* -EAGAIN if you need to retry, -EFAULT invalid (ie either no valid
* -EBUSY if you need to retry, -EFAULT invalid (ie either no valid
* vma or it is illegal to access that range), number of valid pages
* in range->pfns[] (from range start address).
*
@ -967,7 +967,7 @@ long hmm_range_snapshot(struct hmm_range *range)
do {
/* If range is no longer valid force retry. */
if (!range->valid)
return -EAGAIN;
return -EBUSY;
vma = find_vma(hmm->mm, start);
if (vma == NULL || (vma->vm_flags & device_vma))
@ -1062,10 +1062,8 @@ long hmm_range_fault(struct hmm_range *range, bool block)
do {
/* If range is no longer valid force retry. */
if (!range->valid) {
up_read(&hmm->mm->mmap_sem);
return -EAGAIN;
}
if (!range->valid)
return -EBUSY;
vma = find_vma(hmm->mm, start);
if (vma == NULL || (vma->vm_flags & device_vma))