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mm/hmm/mirror: device page fault handler

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This handles page fault on behalf of device driver, unlike
handle_mm_fault() it does not trigger migration back to system memory for
device memory.

Link: http://lkml.kernel.org/r/20170817000548.32038-6-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Evgeny Baskakov <ebaskakov@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Mark Hairgrove <mhairgrove@nvidia.com>
Signed-off-by: Sherry Cheung <SCheung@nvidia.com>
Signed-off-by: Subhash Gutti <sgutti@nvidia.com>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Nellans <dnellans@nvidia.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Bob Liu <liubo95@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jérôme Glisse 2017-09-08 16:11:35 -07:00 committed by Linus Torvalds
parent da4c3c735e
commit 74eee180b9
2 changed files with 271 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
include/linux/hmm.h
View File

@ -292,6 +292,33 @@ int hmm_vma_get_pfns(struct vm_area_struct *vma,
unsigned long end,
hmm_pfn_t *pfns);
bool hmm_vma_range_done(struct vm_area_struct *vma, struct hmm_range *range);
/*
* Fault memory on behalf of device driver. Unlike handle_mm_fault(), this will
* not migrate any device memory back to system memory. The hmm_pfn_t array will
* be updated with the fault result and current snapshot of the CPU page table
* for the range.
*
* The mmap_sem must be taken in read mode before entering and it might be
* dropped by the function if the block argument is false. In that case, the
* function returns -EAGAIN.
*
* Return value does not reflect if the fault was successful for every single
* address or not. Therefore, the caller must to inspect the hmm_pfn_t array to
* determine fault status for each address.
*
* Trying to fault inside an invalid vma will result in -EINVAL.
*
* See the function description in mm/hmm.c for further documentation.
*/
int hmm_vma_fault(struct vm_area_struct *vma,
struct hmm_range *range,
unsigned long start,
unsigned long end,
hmm_pfn_t *pfns,
bool write,
bool block);
#endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */

256
mm/hmm.c
View File

@ -221,6 +221,36 @@ void hmm_mirror_unregister(struct hmm_mirror *mirror)
}
EXPORT_SYMBOL(hmm_mirror_unregister);
struct hmm_vma_walk {
struct hmm_range *range;
unsigned long last;
bool fault;
bool block;
bool write;
};
static int hmm_vma_do_fault(struct mm_walk *walk,
unsigned long addr,
hmm_pfn_t *pfn)
{
unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_REMOTE;
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct vm_area_struct *vma = walk->vma;
int r;
flags |= hmm_vma_walk->block ? 0 : FAULT_FLAG_ALLOW_RETRY;
flags |= hmm_vma_walk->write ? FAULT_FLAG_WRITE : 0;
r = handle_mm_fault(vma, addr, flags);
if (r & VM_FAULT_RETRY)
return -EBUSY;
if (r & VM_FAULT_ERROR) {
*pfn = HMM_PFN_ERROR;
return -EFAULT;
}
return -EAGAIN;
}
static void hmm_pfns_special(hmm_pfn_t *pfns,
unsigned long addr,
unsigned long end)
@ -244,34 +274,62 @@ static int hmm_pfns_bad(unsigned long addr,
return 0;
}
static void hmm_pfns_clear(hmm_pfn_t *pfns,
unsigned long addr,
unsigned long end)
{
for (; addr < end; addr += PAGE_SIZE, pfns++)
*pfns = 0;
}
static int hmm_vma_walk_hole(unsigned long addr,
unsigned long end,
struct mm_walk *walk)
{
struct hmm_range *range = walk->private;
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
hmm_pfn_t *pfns = range->pfns;
unsigned long i;
hmm_vma_walk->last = addr;
i = (addr - range->start) >> PAGE_SHIFT;
for (; addr < end; addr += PAGE_SIZE, i++)
for (; addr < end; addr += PAGE_SIZE, i++) {
pfns[i] = HMM_PFN_EMPTY;
if (hmm_vma_walk->fault) {
int ret;
return 0;
ret = hmm_vma_do_fault(walk, addr, &pfns[i]);
if (ret != -EAGAIN)
return ret;
}
}
return hmm_vma_walk->fault ? -EAGAIN : 0;
}
static int hmm_vma_walk_clear(unsigned long addr,
unsigned long end,
struct mm_walk *walk)
{
struct hmm_range *range = walk->private;
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
hmm_pfn_t *pfns = range->pfns;
unsigned long i;
hmm_vma_walk->last = addr;
i = (addr - range->start) >> PAGE_SHIFT;
for (; addr < end; addr += PAGE_SIZE, i++)
for (; addr < end; addr += PAGE_SIZE, i++) {
pfns[i] = 0;
if (hmm_vma_walk->fault) {
int ret;
return 0;
ret = hmm_vma_do_fault(walk, addr, &pfns[i]);
if (ret != -EAGAIN)
return ret;
}
}
return hmm_vma_walk->fault ? -EAGAIN : 0;
}
static int hmm_vma_walk_pmd(pmd_t *pmdp,
@ -279,15 +337,18 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
unsigned long end,
struct mm_walk *walk)
{
struct hmm_range *range = walk->private;
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
struct vm_area_struct *vma = walk->vma;
hmm_pfn_t *pfns = range->pfns;
unsigned long addr = start, i;
bool write_fault;
hmm_pfn_t flag;
pte_t *ptep;
i = (addr - range->start) >> PAGE_SHIFT;
flag = vma->vm_flags & VM_READ ? HMM_PFN_READ : 0;
write_fault = hmm_vma_walk->fault & hmm_vma_walk->write;
again:
if (pmd_none(*pmdp))
@ -316,6 +377,9 @@ again:
if (pmd_protnone(pmd))
return hmm_vma_walk_clear(start, end, walk);
if (write_fault && !pmd_write(pmd))
return hmm_vma_walk_clear(start, end, walk);
pfn = pmd_pfn(pmd) + pte_index(addr);
flag |= pmd_write(pmd) ? HMM_PFN_WRITE : 0;
for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
@ -332,13 +396,55 @@ again:
pfns[i] = 0;
if (pte_none(pte) || !pte_present(pte)) {
if (pte_none(pte)) {
pfns[i] = HMM_PFN_EMPTY;
if (hmm_vma_walk->fault)
goto fault;
continue;
}
if (!pte_present(pte)) {
swp_entry_t entry;
if (!non_swap_entry(entry)) {
if (hmm_vma_walk->fault)
goto fault;
continue;
}
entry = pte_to_swp_entry(pte);
/*
* This is a special swap entry, ignore migration, use
* device and report anything else as error.
*/
if (is_migration_entry(entry)) {
if (hmm_vma_walk->fault) {
pte_unmap(ptep);
hmm_vma_walk->last = addr;
migration_entry_wait(vma->vm_mm,
pmdp, addr);
return -EAGAIN;
}
continue;
} else {
/* Report error for everything else */
pfns[i] = HMM_PFN_ERROR;
}
continue;
}
if (write_fault && !pte_write(pte))
goto fault;
pfns[i] = hmm_pfn_t_from_pfn(pte_pfn(pte)) | flag;
pfns[i] |= pte_write(pte) ? HMM_PFN_WRITE : 0;
continue;
fault:
pte_unmap(ptep);
/* Fault all pages in range */
return hmm_vma_walk_clear(start, end, walk);
}
pte_unmap(ptep - 1);
@ -371,6 +477,7 @@ int hmm_vma_get_pfns(struct vm_area_struct *vma,
unsigned long end,
hmm_pfn_t *pfns)
{
struct hmm_vma_walk hmm_vma_walk;
struct mm_walk mm_walk;
struct hmm *hmm;
@ -402,9 +509,12 @@ int hmm_vma_get_pfns(struct vm_area_struct *vma,
list_add_rcu(&range->list, &hmm->ranges);
spin_unlock(&hmm->lock);
hmm_vma_walk.fault = false;
hmm_vma_walk.range = range;
mm_walk.private = &hmm_vma_walk;
mm_walk.vma = vma;
mm_walk.mm = vma->vm_mm;
mm_walk.private = range;
mm_walk.pte_entry = NULL;
mm_walk.test_walk = NULL;
mm_walk.hugetlb_entry = NULL;
@ -412,7 +522,6 @@ int hmm_vma_get_pfns(struct vm_area_struct *vma,
mm_walk.pte_hole = hmm_vma_walk_hole;
walk_page_range(start, end, &mm_walk);
return 0;
}
EXPORT_SYMBOL(hmm_vma_get_pfns);
@ -439,7 +548,7 @@ EXPORT_SYMBOL(hmm_vma_get_pfns);
*
* There are two ways to use this :
* again:
* hmm_vma_get_pfns(vma, range, start, end, pfns);
* hmm_vma_get_pfns(vma, range, start, end, pfns); or hmm_vma_fault(...);
* trans = device_build_page_table_update_transaction(pfns);
* device_page_table_lock();
* if (!hmm_vma_range_done(vma, range)) {
@ -450,7 +559,7 @@ EXPORT_SYMBOL(hmm_vma_get_pfns);
* device_page_table_unlock();
*
* Or:
* hmm_vma_get_pfns(vma, range, start, end, pfns);
* hmm_vma_get_pfns(vma, range, start, end, pfns); or hmm_vma_fault(...);
* device_page_table_lock();
* hmm_vma_range_done(vma, range);
* device_update_page_table(pfns);
@ -479,4 +588,127 @@ bool hmm_vma_range_done(struct vm_area_struct *vma, struct hmm_range *range)
return range->valid;
}
EXPORT_SYMBOL(hmm_vma_range_done);
/*
* hmm_vma_fault() - try to fault some address in a virtual address range
* @vma: virtual memory area containing the virtual address range
* @range: use to track pfns array content validity
* @start: fault range virtual start address (inclusive)
* @end: fault range virtual end address (exclusive)
* @pfns: array of hmm_pfn_t, only entry with fault flag set will be faulted
* @write: is it a write fault
* @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
* Returns: 0 success, error otherwise (-EAGAIN means mmap_sem have been drop)
*
* This is similar to a regular CPU page fault except that it will not trigger
* any memory migration if the memory being faulted is not accessible by CPUs.
*
* On error, for one virtual address in the range, the function will set the
* hmm_pfn_t error flag for the corresponding pfn entry.
*
* Expected use pattern:
* retry:
* down_read(&mm->mmap_sem);
* // Find vma and address device wants to fault, initialize hmm_pfn_t
* // array accordingly
* ret = hmm_vma_fault(vma, start, end, pfns, allow_retry);
* switch (ret) {
* case -EAGAIN:
* hmm_vma_range_done(vma, range);
* // You might want to rate limit or yield to play nicely, you may
* // also commit any valid pfn in the array assuming that you are
* // getting true from hmm_vma_range_monitor_end()
* goto retry;
* case 0:
* break;
* default:
* // Handle error !
* up_read(&mm->mmap_sem)
* return;
* }
* // Take device driver lock that serialize device page table update
* driver_lock_device_page_table_update();
* hmm_vma_range_done(vma, range);
* // Commit pfns we got from hmm_vma_fault()
* driver_unlock_device_page_table_update();
* up_read(&mm->mmap_sem)
*
* YOU MUST CALL hmm_vma_range_done() AFTER THIS FUNCTION RETURN SUCCESS (0)
* BEFORE FREEING THE range struct OR YOU WILL HAVE SERIOUS MEMORY CORRUPTION !
*
* YOU HAVE BEEN WARNED !
*/
int hmm_vma_fault(struct vm_area_struct *vma,
struct hmm_range *range,
unsigned long start,
unsigned long end,
hmm_pfn_t *pfns,
bool write,
bool block)
{
struct hmm_vma_walk hmm_vma_walk;
struct mm_walk mm_walk;
struct hmm *hmm;
int ret;
/* Sanity check, this really should not happen ! */
if (start < vma->vm_start || start >= vma->vm_end)
return -EINVAL;
if (end < vma->vm_start || end > vma->vm_end)
return -EINVAL;
hmm = hmm_register(vma->vm_mm);
if (!hmm) {
hmm_pfns_clear(pfns, start, end);
return -ENOMEM;
}
/* Caller must have registered a mirror using hmm_mirror_register() */
if (!hmm->mmu_notifier.ops)
return -EINVAL;
/* Initialize range to track CPU page table update */
range->start = start;
range->pfns = pfns;
range->end = end;
spin_lock(&hmm->lock);
range->valid = true;
list_add_rcu(&range->list, &hmm->ranges);
spin_unlock(&hmm->lock);
/* FIXME support hugetlb fs */
if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
hmm_pfns_special(pfns, start, end);
return 0;
}
hmm_vma_walk.fault = true;
hmm_vma_walk.write = write;
hmm_vma_walk.block = block;
hmm_vma_walk.range = range;
mm_walk.private = &hmm_vma_walk;
hmm_vma_walk.last = range->start;
mm_walk.vma = vma;
mm_walk.mm = vma->vm_mm;
mm_walk.pte_entry = NULL;
mm_walk.test_walk = NULL;
mm_walk.hugetlb_entry = NULL;
mm_walk.pmd_entry = hmm_vma_walk_pmd;
mm_walk.pte_hole = hmm_vma_walk_hole;
do {
ret = walk_page_range(start, end, &mm_walk);
start = hmm_vma_walk.last;
} while (ret == -EAGAIN);
if (ret) {
unsigned long i;
i = (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
hmm_pfns_clear(&pfns[i], hmm_vma_walk.last, end);
hmm_vma_range_done(vma, range);
}
return ret;
}
EXPORT_SYMBOL(hmm_vma_fault);
#endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */