| Message ID | 20190722154210.42799-14-steven.price@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Generic page walk and ptdump | expand |
On 07/22/2019 09:12 PM, Steven Price wrote: > It is useful to be able to skip parts of the page table tree even when > walking without VMAs. Add test_p?d callbacks similar to test_walk but > which are called just before a table at that level is walked. If the > callback returns non-zero then the entire table is skipped. > > Signed-off-by: Steven Price <steven.price@arm.com> > --- > include/linux/mm.h | 11 +++++++++++ > mm/pagewalk.c | 24 ++++++++++++++++++++++++ > 2 files changed, 35 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index b22799129128..325a1ca6f820 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1447,6 +1447,11 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma, > * value means "do page table walk over the current vma," > * and a negative one means "abort current page table walk > * right now." 1 means "skip the current vma." > + * @test_pmd: similar to test_walk(), but called for every pmd. > + * @test_pud: similar to test_walk(), but called for every pud. > + * @test_p4d: similar to test_walk(), but called for every p4d. > + * Returning 0 means walk this part of the page tables, > + * returning 1 means to skip this range. > * @mm: mm_struct representing the target process of page table walk > * @vma: vma currently walked (NULL if walking outside vmas) > * @private: private data for callbacks' usage > @@ -1471,6 +1476,12 @@ struct mm_walk { > struct mm_walk *walk); > int (*test_walk)(unsigned long addr, unsigned long next, > struct mm_walk *walk); > + int (*test_pmd)(unsigned long addr, unsigned long next, > + pmd_t *pmd_start, struct mm_walk *walk); > + int (*test_pud)(unsigned long addr, unsigned long next, > + pud_t *pud_start, struct mm_walk *walk); > + int (*test_p4d)(unsigned long addr, unsigned long next, > + p4d_t *p4d_start, struct mm_walk *walk); > struct mm_struct *mm; > struct vm_area_struct *vma; > void *private; > diff --git a/mm/pagewalk.c b/mm/pagewalk.c > index 1cbef99e9258..6bea79b95be3 100644 > --- a/mm/pagewalk.c > +++ b/mm/pagewalk.c > @@ -32,6 +32,14 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, > unsigned long next; > int err = 0; > > + if (walk->test_pmd) { > + err = walk->test_pmd(addr, end, pmd_offset(pud, 0UL), walk); > + if (err < 0) > + return err; > + if (err > 0) > + return 0; > + } Though this attempts to match semantics with test_walk() and be comprehensive just wondering what are the real world situations when page walking need to be aborted based on error condition at a given page table level.
On 28/07/2019 14:41, Anshuman Khandual wrote: > > > On 07/22/2019 09:12 PM, Steven Price wrote: >> It is useful to be able to skip parts of the page table tree even when >> walking without VMAs. Add test_p?d callbacks similar to test_walk but >> which are called just before a table at that level is walked. If the >> callback returns non-zero then the entire table is skipped. >> >> Signed-off-by: Steven Price <steven.price@arm.com> >> --- >> include/linux/mm.h | 11 +++++++++++ >> mm/pagewalk.c | 24 ++++++++++++++++++++++++ >> 2 files changed, 35 insertions(+) >> >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index b22799129128..325a1ca6f820 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -1447,6 +1447,11 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma, >> * value means "do page table walk over the current vma," >> * and a negative one means "abort current page table walk >> * right now." 1 means "skip the current vma." >> + * @test_pmd: similar to test_walk(), but called for every pmd. >> + * @test_pud: similar to test_walk(), but called for every pud. >> + * @test_p4d: similar to test_walk(), but called for every p4d. >> + * Returning 0 means walk this part of the page tables, >> + * returning 1 means to skip this range. >> * @mm: mm_struct representing the target process of page table walk >> * @vma: vma currently walked (NULL if walking outside vmas) >> * @private: private data for callbacks' usage >> @@ -1471,6 +1476,12 @@ struct mm_walk { >> struct mm_walk *walk); >> int (*test_walk)(unsigned long addr, unsigned long next, >> struct mm_walk *walk); >> + int (*test_pmd)(unsigned long addr, unsigned long next, >> + pmd_t *pmd_start, struct mm_walk *walk); >> + int (*test_pud)(unsigned long addr, unsigned long next, >> + pud_t *pud_start, struct mm_walk *walk); >> + int (*test_p4d)(unsigned long addr, unsigned long next, >> + p4d_t *p4d_start, struct mm_walk *walk); >> struct mm_struct *mm; >> struct vm_area_struct *vma; >> void *private; >> diff --git a/mm/pagewalk.c b/mm/pagewalk.c >> index 1cbef99e9258..6bea79b95be3 100644 >> --- a/mm/pagewalk.c >> +++ b/mm/pagewalk.c >> @@ -32,6 +32,14 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, >> unsigned long next; >> int err = 0; >> >> + if (walk->test_pmd) { >> + err = walk->test_pmd(addr, end, pmd_offset(pud, 0UL), walk); >> + if (err < 0) >> + return err; >> + if (err > 0) >> + return 0; >> + } > > Though this attempts to match semantics with test_walk() and be comprehensive > just wondering what are the real world situations when page walking need to be > aborted based on error condition at a given page table level. I'm not aware of a situation yet where aborting early is necessary - but as you say this matches the semantics of test_walk() and was easy to implement. Steve
diff --git a/include/linux/mm.h b/include/linux/mm.h index b22799129128..325a1ca6f820 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1447,6 +1447,11 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma, * value means "do page table walk over the current vma," * and a negative one means "abort current page table walk * right now." 1 means "skip the current vma." + * @test_pmd: similar to test_walk(), but called for every pmd. + * @test_pud: similar to test_walk(), but called for every pud. + * @test_p4d: similar to test_walk(), but called for every p4d. + * Returning 0 means walk this part of the page tables, + * returning 1 means to skip this range. * @mm: mm_struct representing the target process of page table walk * @vma: vma currently walked (NULL if walking outside vmas) * @private: private data for callbacks' usage @@ -1471,6 +1476,12 @@ struct mm_walk { struct mm_walk *walk); int (*test_walk)(unsigned long addr, unsigned long next, struct mm_walk *walk); + int (*test_pmd)(unsigned long addr, unsigned long next, + pmd_t *pmd_start, struct mm_walk *walk); + int (*test_pud)(unsigned long addr, unsigned long next, + pud_t *pud_start, struct mm_walk *walk); + int (*test_p4d)(unsigned long addr, unsigned long next, + p4d_t *p4d_start, struct mm_walk *walk); struct mm_struct *mm; struct vm_area_struct *vma; void *private; diff --git a/mm/pagewalk.c b/mm/pagewalk.c index 1cbef99e9258..6bea79b95be3 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -32,6 +32,14 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, unsigned long next; int err = 0; + if (walk->test_pmd) { + err = walk->test_pmd(addr, end, pmd_offset(pud, 0UL), walk); + if (err < 0) + return err; + if (err > 0) + return 0; + } + pmd = pmd_offset(pud, addr); do { again: @@ -82,6 +90,14 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end, unsigned long next; int err = 0; + if (walk->test_pud) { + err = walk->test_pud(addr, end, pud_offset(p4d, 0UL), walk); + if (err < 0) + return err; + if (err > 0) + return 0; + } + pud = pud_offset(p4d, addr); do { again: @@ -124,6 +140,14 @@ static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end, unsigned long next; int err = 0; + if (walk->test_p4d) { + err = walk->test_p4d(addr, end, p4d_offset(pgd, 0UL), walk); + if (err < 0) + return err; + if (err > 0) + return 0; + } + p4d = p4d_offset(pgd, addr); do { next = p4d_addr_end(addr, end);
It is useful to be able to skip parts of the page table tree even when walking without VMAs. Add test_p?d callbacks similar to test_walk but which are called just before a table at that level is walked. If the callback returns non-zero then the entire table is skipped. Signed-off-by: Steven Price <steven.price@arm.com> --- include/linux/mm.h | 11 +++++++++++ mm/pagewalk.c | 24 ++++++++++++++++++++++++ 2 files changed, 35 insertions(+)