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mm/hmm/mirror: helper to snapshot CPU page table

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This does not use existing page table walker because we want to share
same code for our page fault handler.

Link: http://lkml.kernel.org/r/20170817000548.32038-5-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 16:11:31 -07:00 committed by Linus Torvalds
parent c0b124054f
commit da4c3c735e
2 changed files with 338 additions and 2 deletions
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55
include/linux/hmm.h
View File

@ -79,13 +79,26 @@ struct hmm;
*
* Flags:
* HMM_PFN_VALID: pfn is valid
* HMM_PFN_READ: CPU page table has read permission set
* HMM_PFN_WRITE: CPU page table has write permission set
* HMM_PFN_ERROR: corresponding CPU page table entry points to poisoned memory
* HMM_PFN_EMPTY: corresponding CPU page table entry is pte_none()
* HMM_PFN_SPECIAL: corresponding CPU page table entry is special; i.e., the
* result of vm_insert_pfn() or vm_insert_page(). Therefore, it should not
* be mirrored by a device, because the entry will never have HMM_PFN_VALID
* set and the pfn value is undefined.
* HMM_PFN_DEVICE_UNADDRESSABLE: unaddressable device memory (ZONE_DEVICE)
*/
typedef unsigned long hmm_pfn_t;
#define HMM_PFN_VALID (1 << 0)
#define HMM_PFN_WRITE (1 << 1)
#define HMM_PFN_SHIFT 2
#define HMM_PFN_READ (1 << 1)
#define HMM_PFN_WRITE (1 << 2)
#define HMM_PFN_ERROR (1 << 3)
#define HMM_PFN_EMPTY (1 << 4)
#define HMM_PFN_SPECIAL (1 << 5)
#define HMM_PFN_DEVICE_UNADDRESSABLE (1 << 6)
#define HMM_PFN_SHIFT 7
/*
* hmm_pfn_t_to_page() - return struct page pointed to by a valid hmm_pfn_t
@ -241,6 +254,44 @@ struct hmm_mirror {
int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm);
void hmm_mirror_unregister(struct hmm_mirror *mirror);
/*
* struct hmm_range - track invalidation lock on virtual address range
*
* @list: all range lock are on a list
* @start: range virtual start address (inclusive)
* @end: range virtual end address (exclusive)
* @pfns: array of pfns (big enough for the range)
* @valid: pfns array did not change since it has been fill by an HMM function
*/
struct hmm_range {
struct list_head list;
unsigned long start;
unsigned long end;
hmm_pfn_t *pfns;
bool valid;
};
/*
* To snapshot the CPU page table, call hmm_vma_get_pfns(), then take a device
* driver lock that serializes device page table updates, then call
* hmm_vma_range_done(), to check if the snapshot is still valid. The same
* device driver page table update lock must also be used in the
* hmm_mirror_ops.sync_cpu_device_pagetables() callback, so that CPU page
* table invalidation serializes on it.
*
* YOU MUST CALL hmm_vma_range_done() ONCE AND ONLY ONCE EACH TIME YOU CALL
* hmm_vma_get_pfns() WITHOUT ERROR !
*
* IF YOU DO NOT FOLLOW THE ABOVE RULE THE SNAPSHOT CONTENT MIGHT BE INVALID !
*/
int hmm_vma_get_pfns(struct vm_area_struct *vma,
struct hmm_range *range,
unsigned long start,
unsigned long end,
hmm_pfn_t *pfns);
bool hmm_vma_range_done(struct vm_area_struct *vma, struct hmm_range *range);
#endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */

285
mm/hmm.c
View File

@ -19,8 +19,12 @@
*/
#include <linux/mm.h>
#include <linux/hmm.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/swapops.h>
#include <linux/hugetlb.h>
#include <linux/mmu_notifier.h>
@ -31,14 +35,18 @@ static const struct mmu_notifier_ops hmm_mmu_notifier_ops;
* struct hmm - HMM per mm struct
*
* @mm: mm struct this HMM struct is bound to
* @lock: lock protecting ranges list
* @sequence: we track updates to the CPU page table with a sequence number
* @ranges: list of range being snapshotted
* @mirrors: list of mirrors for this mm
* @mmu_notifier: mmu notifier to track updates to CPU page table
* @mirrors_sem: read/write semaphore protecting the mirrors list
*/
struct hmm {
struct mm_struct *mm;
spinlock_t lock;
atomic_t sequence;
struct list_head ranges;
struct list_head mirrors;
struct mmu_notifier mmu_notifier;
struct rw_semaphore mirrors_sem;
@ -72,6 +80,8 @@ static struct hmm *hmm_register(struct mm_struct *mm)
init_rwsem(&hmm->mirrors_sem);
atomic_set(&hmm->sequence, 0);
hmm->mmu_notifier.ops = NULL;
INIT_LIST_HEAD(&hmm->ranges);
spin_lock_init(&hmm->lock);
hmm->mm = mm;
/*
@ -112,6 +122,22 @@ static void hmm_invalidate_range(struct hmm *hmm,
unsigned long end)
{
struct hmm_mirror *mirror;
struct hmm_range *range;
spin_lock(&hmm->lock);
list_for_each_entry(range, &hmm->ranges, list) {
unsigned long addr, idx, npages;
if (end < range->start || start >= range->end)
continue;
range->valid = false;
addr = max(start, range->start);
idx = (addr - range->start) >> PAGE_SHIFT;
npages = (min(range->end, end) - addr) >> PAGE_SHIFT;
memset(&range->pfns[idx], 0, sizeof(*range->pfns) * npages);
}
spin_unlock(&hmm->lock);
down_read(&hmm->mirrors_sem);
list_for_each_entry(mirror, &hmm->mirrors, list)
@ -194,4 +220,263 @@ void hmm_mirror_unregister(struct hmm_mirror *mirror)
up_write(&hmm->mirrors_sem);
}
EXPORT_SYMBOL(hmm_mirror_unregister);
static void hmm_pfns_special(hmm_pfn_t *pfns,
unsigned long addr,
unsigned long end)
{
for (; addr < end; addr += PAGE_SIZE, pfns++)
*pfns = HMM_PFN_SPECIAL;
}
static int hmm_pfns_bad(unsigned long addr,
unsigned long end,
struct mm_walk *walk)
{
struct hmm_range *range = walk->private;
hmm_pfn_t *pfns = range->pfns;
unsigned long i;
i = (addr - range->start) >> PAGE_SHIFT;
for (; addr < end; addr += PAGE_SIZE, i++)
pfns[i] = HMM_PFN_ERROR;
return 0;
}
static int hmm_vma_walk_hole(unsigned long addr,
unsigned long end,
struct mm_walk *walk)
{
struct hmm_range *range = walk->private;
hmm_pfn_t *pfns = range->pfns;
unsigned long i;
i = (addr - range->start) >> PAGE_SHIFT;
for (; addr < end; addr += PAGE_SIZE, i++)
pfns[i] = HMM_PFN_EMPTY;
return 0;
}
static int hmm_vma_walk_clear(unsigned long addr,
unsigned long end,
struct mm_walk *walk)
{
struct hmm_range *range = walk->private;
hmm_pfn_t *pfns = range->pfns;
unsigned long i;
i = (addr - range->start) >> PAGE_SHIFT;
for (; addr < end; addr += PAGE_SIZE, i++)
pfns[i] = 0;
return 0;
}
static int hmm_vma_walk_pmd(pmd_t *pmdp,
unsigned long start,
unsigned long end,
struct mm_walk *walk)
{
struct hmm_range *range = walk->private;
struct vm_area_struct *vma = walk->vma;
hmm_pfn_t *pfns = range->pfns;
unsigned long addr = start, i;
hmm_pfn_t flag;
pte_t *ptep;
i = (addr - range->start) >> PAGE_SHIFT;
flag = vma->vm_flags & VM_READ ? HMM_PFN_READ : 0;
again:
if (pmd_none(*pmdp))
return hmm_vma_walk_hole(start, end, walk);
if (pmd_huge(*pmdp) && vma->vm_flags & VM_HUGETLB)
return hmm_pfns_bad(start, end, walk);
if (pmd_devmap(*pmdp) || pmd_trans_huge(*pmdp)) {
unsigned long pfn;
pmd_t pmd;
/*
* No need to take pmd_lock here, even if some other threads
* is splitting the huge pmd we will get that event through
* mmu_notifier callback.
*
* So just read pmd value and check again its a transparent
* huge or device mapping one and compute corresponding pfn
* values.
*/
pmd = pmd_read_atomic(pmdp);
barrier();
if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
goto again;
if (pmd_protnone(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++)
pfns[i] = hmm_pfn_t_from_pfn(pfn) | flag;
return 0;
}
if (pmd_bad(*pmdp))
return hmm_pfns_bad(start, end, walk);
ptep = pte_offset_map(pmdp, addr);
for (; addr < end; addr += PAGE_SIZE, ptep++, i++) {
pte_t pte = *ptep;
pfns[i] = 0;
if (pte_none(pte) || !pte_present(pte)) {
pfns[i] = HMM_PFN_EMPTY;
continue;
}
pfns[i] = hmm_pfn_t_from_pfn(pte_pfn(pte)) | flag;
pfns[i] |= pte_write(pte) ? HMM_PFN_WRITE : 0;
}
pte_unmap(ptep - 1);
return 0;
}
/*
* hmm_vma_get_pfns() - snapshot CPU page table for a range of virtual addresses
* @vma: virtual memory area containing the virtual address range
* @range: used to track snapshot validity
* @start: range virtual start address (inclusive)
* @end: range virtual end address (exclusive)
* @entries: array of hmm_pfn_t: provided by the caller, filled in by function
* Returns: -EINVAL if invalid argument, -ENOMEM out of memory, 0 success
*
* This snapshots the CPU page table for a range of virtual addresses. Snapshot
* validity is tracked by range struct. See hmm_vma_range_done() for further
* information.
*
* The range struct is initialized here. It tracks the CPU page table, but only
* if the function returns success (0), in which case the caller must then call
* hmm_vma_range_done() to stop CPU page table update tracking on this range.
*
* NOT CALLING hmm_vma_range_done() IF FUNCTION RETURNS 0 WILL LEAD TO SERIOUS
* MEMORY CORRUPTION ! YOU HAVE BEEN WARNED !
*/
int hmm_vma_get_pfns(struct vm_area_struct *vma,
struct hmm_range *range,
unsigned long start,
unsigned long end,
hmm_pfn_t *pfns)
{
struct mm_walk mm_walk;
struct hmm *hmm;
/* FIXME support hugetlb fs */
if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
hmm_pfns_special(pfns, start, end);
return -EINVAL;
}
/* 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)
return -ENOMEM;
/* Caller must have registered a mirror, via 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);
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;
mm_walk.pmd_entry = hmm_vma_walk_pmd;
mm_walk.pte_hole = hmm_vma_walk_hole;
walk_page_range(start, end, &mm_walk);
return 0;
}
EXPORT_SYMBOL(hmm_vma_get_pfns);
/*
* hmm_vma_range_done() - stop tracking change to CPU page table over a range
* @vma: virtual memory area containing the virtual address range
* @range: range being tracked
* Returns: false if range data has been invalidated, true otherwise
*
* Range struct is used to track updates to the CPU page table after a call to
* either hmm_vma_get_pfns() or hmm_vma_fault(). Once the device driver is done
* using the data, or wants to lock updates to the data it got from those
* functions, it must call the hmm_vma_range_done() function, which will then
* stop tracking CPU page table updates.
*
* Note that device driver must still implement general CPU page table update
* tracking either by using hmm_mirror (see hmm_mirror_register()) or by using
* the mmu_notifier API directly.
*
* CPU page table update tracking done through hmm_range is only temporary and
* to be used while trying to duplicate CPU page table contents for a range of
* virtual addresses.
*
* There are two ways to use this :
* again:
* hmm_vma_get_pfns(vma, range, start, end, pfns);
* trans = device_build_page_table_update_transaction(pfns);
* device_page_table_lock();
* if (!hmm_vma_range_done(vma, range)) {
* device_page_table_unlock();
* goto again;
* }
* device_commit_transaction(trans);
* device_page_table_unlock();
*
* Or:
* hmm_vma_get_pfns(vma, range, start, end, pfns);
* device_page_table_lock();
* hmm_vma_range_done(vma, range);
* device_update_page_table(pfns);
* device_page_table_unlock();
*/
bool hmm_vma_range_done(struct vm_area_struct *vma, struct hmm_range *range)
{
unsigned long npages = (range->end - range->start) >> PAGE_SHIFT;
struct hmm *hmm;
if (range->end <= range->start) {
BUG();
return false;
}
hmm = hmm_register(vma->vm_mm);
if (!hmm) {
memset(range->pfns, 0, sizeof(*range->pfns) * npages);
return false;
}
spin_lock(&hmm->lock);
list_del_rcu(&range->list);
spin_unlock(&hmm->lock);
return range->valid;
}
EXPORT_SYMBOL(hmm_vma_range_done);
#endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */