lkml.org 
[lkml]   [2020]   [Jan]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH RFC 04/10] mm: Handle pud entries in follow_pfn()
Date
When follow_pfn hits a pud_huge() it won't return a valid PFN
for a PUD. Fix it by adding @pudp and thus allow callers to
get the pud pointer. If we encounter such a huge page, we
calculate the offset to the PUD accordingly.

This allows KVM to handle 1G hugepage pfns on VM_PFNMAP vmas.

Co-developed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Signed-off-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
mm/memory.c | 58 ++++++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 49 insertions(+), 9 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 109643219e1b..f46646630497 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4261,9 +4261,10 @@ int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
}
#endif /* __PAGETABLE_PMD_FOLDED */

-static int __follow_pte_pmd(struct mm_struct *mm, unsigned long address,
+static int __follow_pte_pud(struct mm_struct *mm, unsigned long address,
struct mmu_notifier_range *range,
- pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp)
+ pte_t **ptepp, pmd_t **pmdpp, pud_t **pudpp,
+ spinlock_t **ptlp)
{
pgd_t *pgd;
p4d_t *p4d;
@@ -4280,6 +4281,28 @@ static int __follow_pte_pmd(struct mm_struct *mm, unsigned long address,
goto out;

pud = pud_offset(p4d, address);
+ VM_BUG_ON(pud_trans_huge(*pud));
+
+ if (pud_huge(*pud)) {
+ if (!pudpp)
+ goto out;
+
+ if (range) {
+ mmu_notifier_range_init(range, MMU_NOTIFY_CLEAR, 0,
+ NULL, mm, address & PUD_MASK,
+ (address & PUD_MASK) + PUD_SIZE);
+ mmu_notifier_invalidate_range_start(range);
+ }
+ *ptlp = pud_lock(mm, pud);
+ if (pud_huge(*pud)) {
+ *pudpp = pud;
+ return 0;
+ }
+ spin_unlock(*ptlp);
+ if (range)
+ mmu_notifier_invalidate_range_end(range);
+ }
+
if (pud_none(*pud) || unlikely(pud_bad(*pud)))
goto out;

@@ -4335,8 +4358,8 @@ static inline int follow_pte(struct mm_struct *mm, unsigned long address,

/* (void) is needed to make gcc happy */
(void) __cond_lock(*ptlp,
- !(res = __follow_pte_pmd(mm, address, NULL,
- ptepp, NULL, ptlp)));
+ !(res = __follow_pte_pud(mm, address, NULL,
+ ptepp, NULL, NULL, ptlp)));
return res;
}

@@ -4348,12 +4371,26 @@ int follow_pte_pmd(struct mm_struct *mm, unsigned long address,

/* (void) is needed to make gcc happy */
(void) __cond_lock(*ptlp,
- !(res = __follow_pte_pmd(mm, address, range,
- ptepp, pmdpp, ptlp)));
+ !(res = __follow_pte_pud(mm, address, range,
+ ptepp, pmdpp, NULL, ptlp)));
return res;
}
EXPORT_SYMBOL(follow_pte_pmd);

+static int follow_pte_pud(struct mm_struct *mm, unsigned long address,
+ struct mmu_notifier_range *range,
+ pte_t **ptepp, pmd_t **pmdpp, pud_t **pudpp,
+ spinlock_t **ptlp)
+{
+ int res;
+
+ /* (void) is needed to make gcc happy */
+ (void) __cond_lock(*ptlp,
+ !(res = __follow_pte_pud(mm, address, range,
+ ptepp, pmdpp, pudpp, ptlp)));
+ return res;
+}
+
/**
* follow_pfn - look up PFN at a user virtual address
* @vma: memory mapping
@@ -4368,6 +4405,7 @@ int follow_pfn(struct vm_area_struct *vma, unsigned long address,
unsigned long *pfn)
{
pmd_t *pmdpp = NULL;
+ pud_t *pudpp = NULL;
int ret = -EINVAL;
spinlock_t *ptl;
pte_t *ptep;
@@ -4375,11 +4413,13 @@ int follow_pfn(struct vm_area_struct *vma, unsigned long address,
if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
return ret;

- ret = follow_pte_pmd(vma->vm_mm, address, NULL,
- &ptep, &pmdpp, &ptl);
+ ret = follow_pte_pud(vma->vm_mm, address, NULL,
+ &ptep, &pmdpp, &pudpp, &ptl);
if (ret)
return ret;
- if (pmdpp)
+ if (pudpp)
+ *pfn = pud_pfn(*pudpp) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
+ else if (pmdpp)
*pfn = pmd_pfn(*pmdpp) + ((address & ~PMD_MASK) >> PAGE_SHIFT);
else
*pfn = pte_pfn(*ptep);
--
2.17.1
\
 
 \ /
  Last update: 2020-01-10 20:08    [W:0.507 / U:0.044 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site