| Message ID | 20240508113419.18620-1-alexghiti@rivosinc.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Merge arm64/riscv hugetlbfs contpte support | expand |
On 08/05/2024 12:34, Alexandre Ghiti wrote: > This patchset intends to merge the contiguous ptes hugetlbfs implementation > of arm64 and riscv. > > Both arm64 and riscv support the use of contiguous ptes to map pages that > are larger than the default page table size, respectively called contpte > and svnapot. > > The riscv implementation differs from the arm64's in that the LSBs of the > pfn of a svnapot pte are used to store the size of the mapping, allowing > for future sizes to be added (for now only 64KB is supported). That's an > issue for the core mm code which expects to find the *real* pfn a pte points > to. Patch 1 fixes that by always returning svnapot ptes with the real pfn > and restores the size of the mapping when it is written to a page table. > > The following patches are just merges of the 2 different implementations > that currently exist in arm64 and riscv which are very similar. It paves > the way to the reuse of the recent contpte THP work by Ryan [1] to avoid > reimplementing the same in riscv. Hi Alexandre, I've skimmed through this series and the one that moves contpte. I can see there is definitely value in sharing the implementation, and the rough shape of things seems appropriate. I had some minor concerns about making it harder to implement potential future arm64 errata workarounds but on reflection, most of the now-shared code is really just wrapping the primitives that are still arch-specific. I'm going to need to spend proper time reviewing it to give detailed feedback, but I'll be out on paternity leave for 3 weeks from end of Monday at the latest. So realistically I won't be able to do the detailed review until at least the first week of June. Some high level thoughts: - huge_ptep_* functions could be working on different sized huge ptes - arm64 supports contpte, pmd, contpmd and pud. Is keeping them in contpte.c appropriate? Perhaps it's better to keep huge_pte and contpte separate? Also, it only works on arm64 because we can get away with calling the lower-level pte functions even when the huge_pte is actually a contpmd/pmd/pud, because the format is the same. That might present challenges to other arches if the format is different? - It might be easier to review if the arm64 stuff is first moved (without changes) then modified to make it suitable for riscv, then for riscv to be hooked up. At the moment I'm trying to follow all 3 parts per-function. Thanks, Ryan > > This patchset was tested by running the libhugetlbfs testsuite with 64KB > and 2MB pages on both architectures (on a 4KB base page size arm64 kernel). > > [1] https://lore.kernel.org/linux-arm-kernel/20240215103205.2607016-1-ryan.roberts@arm.com/ > > Changes in v2: > - Rebase on top of 6.9-rc3 > > Alexandre Ghiti (9): > riscv: Restore the pfn in a NAPOT pte when manipulated by core mm code > riscv: Safely remove huge_pte_offset() when manipulating NAPOT ptes > mm: Use common huge_ptep_get() function for riscv/arm64 > mm: Use common set_huge_pte_at() function for riscv/arm64 > mm: Use common huge_pte_clear() function for riscv/arm64 > mm: Use common huge_ptep_get_and_clear() function for riscv/arm64 > mm: Use common huge_ptep_set_access_flags() function for riscv/arm64 > mm: Use common huge_ptep_set_wrprotect() function for riscv/arm64 > mm: Use common huge_ptep_clear_flush() function for riscv/arm64 > > arch/arm64/Kconfig | 1 + > arch/arm64/include/asm/pgtable.h | 56 +++++- > arch/arm64/mm/hugetlbpage.c | 291 +--------------------------- > arch/riscv/Kconfig | 1 + > arch/riscv/include/asm/hugetlb.h | 2 +- > arch/riscv/include/asm/pgtable-64.h | 11 ++ > arch/riscv/include/asm/pgtable.h | 153 +++++++++++++-- > arch/riscv/mm/hugetlbpage.c | 227 ---------------------- > arch/riscv/mm/pgtable.c | 6 +- > mm/Kconfig | 3 + > mm/Makefile | 1 + > mm/contpte.c | 272 ++++++++++++++++++++++++++ > 12 files changed, 480 insertions(+), 544 deletions(-) > create mode 100644 mm/contpte.c >
Hi Ryan, On Fri, May 10, 2024 at 3:49 PM Ryan Roberts <ryan.roberts@arm.com> wrote: > > On 08/05/2024 12:34, Alexandre Ghiti wrote: > > This patchset intends to merge the contiguous ptes hugetlbfs implementation > > of arm64 and riscv. > > > > Both arm64 and riscv support the use of contiguous ptes to map pages that > > are larger than the default page table size, respectively called contpte > > and svnapot. > > > > The riscv implementation differs from the arm64's in that the LSBs of the > > pfn of a svnapot pte are used to store the size of the mapping, allowing > > for future sizes to be added (for now only 64KB is supported). That's an > > issue for the core mm code which expects to find the *real* pfn a pte points > > to. Patch 1 fixes that by always returning svnapot ptes with the real pfn > > and restores the size of the mapping when it is written to a page table. > > > > The following patches are just merges of the 2 different implementations > > that currently exist in arm64 and riscv which are very similar. It paves > > the way to the reuse of the recent contpte THP work by Ryan [1] to avoid > > reimplementing the same in riscv. > > Hi Alexandre, > > I've skimmed through this series and the one that moves contpte. I can see there > is definitely value in sharing the implementation, and the rough shape of things > seems appropriate. I had some minor concerns about making it harder to implement > potential future arm64 errata workarounds but on reflection, most of the > now-shared code is really just wrapping the primitives that are still arch-specific. > > I'm going to need to spend proper time reviewing it to give detailed feedback, > but I'll be out on paternity leave for 3 weeks from end of Monday at the latest. Too bad, I expected to discuss that with you at LSF/MM...But congrats! Hope your wife is fine :) > So realistically I won't be able to do the detailed review until at least the > first week of June. > > Some high level thoughts: > > - huge_ptep_* functions could be working on different sized huge ptes - arm64 > supports contpte, pmd, contpmd and pud. Is keeping them in contpte.c > appropriate? Hmm indeed, I'll see what I can do. > Perhaps it's better to keep huge_pte and contpte separate? Also, it > only works on arm64 because we can get away with calling the lower-level pte > functions even when the huge_pte is actually a contpmd/pmd/pud, because the > format is the same. That might present challenges to other arches if the format > is different? Yes, but I think that if that happens, we could get away with it by choosing the right function depending on the size of the mapping? > > - It might be easier to review if the arm64 stuff is first moved (without > changes) then modified to make it suitable for riscv, then for riscv to be > hooked up. At the moment I'm trying to follow all 3 parts per-function. Ok, let me give it a try during your paternity leave! > > Thanks, > Ryan Thanks, Alex > > > > > > This patchset was tested by running the libhugetlbfs testsuite with 64KB > > and 2MB pages on both architectures (on a 4KB base page size arm64 kernel). > > > > [1] https://lore.kernel.org/linux-arm-kernel/20240215103205.2607016-1-ryan.roberts@arm.com/ > > > > Changes in v2: > > - Rebase on top of 6.9-rc3 > > > > Alexandre Ghiti (9): > > riscv: Restore the pfn in a NAPOT pte when manipulated by core mm code > > riscv: Safely remove huge_pte_offset() when manipulating NAPOT ptes > > mm: Use common huge_ptep_get() function for riscv/arm64 > > mm: Use common set_huge_pte_at() function for riscv/arm64 > > mm: Use common huge_pte_clear() function for riscv/arm64 > > mm: Use common huge_ptep_get_and_clear() function for riscv/arm64 > > mm: Use common huge_ptep_set_access_flags() function for riscv/arm64 > > mm: Use common huge_ptep_set_wrprotect() function for riscv/arm64 > > mm: Use common huge_ptep_clear_flush() function for riscv/arm64 > > > > arch/arm64/Kconfig | 1 + > > arch/arm64/include/asm/pgtable.h | 56 +++++- > > arch/arm64/mm/hugetlbpage.c | 291 +--------------------------- > > arch/riscv/Kconfig | 1 + > > arch/riscv/include/asm/hugetlb.h | 2 +- > > arch/riscv/include/asm/pgtable-64.h | 11 ++ > > arch/riscv/include/asm/pgtable.h | 153 +++++++++++++-- > > arch/riscv/mm/hugetlbpage.c | 227 ---------------------- > > arch/riscv/mm/pgtable.c | 6 +- > > mm/Kconfig | 3 + > > mm/Makefile | 1 + > > mm/contpte.c | 272 ++++++++++++++++++++++++++ > > 12 files changed, 480 insertions(+), 544 deletions(-) > > create mode 100644 mm/contpte.c > > >
On 12/05/2024 18:25, Alexandre Ghiti wrote: > Hi Ryan, > > On Fri, May 10, 2024 at 3:49 PM Ryan Roberts <ryan.roberts@arm.com> wrote: >> >> On 08/05/2024 12:34, Alexandre Ghiti wrote: >>> This patchset intends to merge the contiguous ptes hugetlbfs implementation >>> of arm64 and riscv. >>> >>> Both arm64 and riscv support the use of contiguous ptes to map pages that >>> are larger than the default page table size, respectively called contpte >>> and svnapot. >>> >>> The riscv implementation differs from the arm64's in that the LSBs of the >>> pfn of a svnapot pte are used to store the size of the mapping, allowing >>> for future sizes to be added (for now only 64KB is supported). That's an >>> issue for the core mm code which expects to find the *real* pfn a pte points >>> to. Patch 1 fixes that by always returning svnapot ptes with the real pfn >>> and restores the size of the mapping when it is written to a page table. >>> >>> The following patches are just merges of the 2 different implementations >>> that currently exist in arm64 and riscv which are very similar. It paves >>> the way to the reuse of the recent contpte THP work by Ryan [1] to avoid >>> reimplementing the same in riscv. >> >> Hi Alexandre, >> >> I've skimmed through this series and the one that moves contpte. I can see there >> is definitely value in sharing the implementation, and the rough shape of things >> seems appropriate. I had some minor concerns about making it harder to implement >> potential future arm64 errata workarounds but on reflection, most of the >> now-shared code is really just wrapping the primitives that are still arch-specific. >> >> I'm going to need to spend proper time reviewing it to give detailed feedback, >> but I'll be out on paternity leave for 3 weeks from end of Monday at the latest. > > Too bad, I expected to discuss that with you at LSF/MM...But congrats! > Hope your wife is fine :) Thanks! Yes its unfortunate timing - there are a few topics I would have liked to get involved with. There's always next year... > >> So realistically I won't be able to do the detailed review until at least the >> first week of June. >> >> Some high level thoughts: >> >> - huge_ptep_* functions could be working on different sized huge ptes - arm64 >> supports contpte, pmd, contpmd and pud. Is keeping them in contpte.c >> appropriate? > > Hmm indeed, I'll see what I can do. > >> Perhaps it's better to keep huge_pte and contpte separate? Also, it >> only works on arm64 because we can get away with calling the lower-level pte >> functions even when the huge_pte is actually a contpmd/pmd/pud, because the >> format is the same. That might present challenges to other arches if the format >> is different? > > Yes, but I think that if that happens, we could get away with it by > choosing the right function depending on the size of the mapping? Yes possibly. One potential future new user of this common code would be arm32 (arch/arm), which also has the contig bit. But AIUI, the pmd an pte formats are quite different. It's likely that arm would want to opt-in to contpte but not huge_ptep, so separate selectors may be valuable. > >> >> - It might be easier to review if the arm64 stuff is first moved (without >> changes) then modified to make it suitable for riscv, then for riscv to be >> hooked up. At the moment I'm trying to follow all 3 parts per-function. > > Ok, let me give it a try during your paternity leave! Thanks! If it's too difficult then it's not a deal-breaker. Perhaps just an initial patch to move the existing arm functions to core-mm without change, then all your existing patches on top of that would do the job? > >> >> Thanks, >> Ryan > > Thanks, > > Alex > >> >> >>> >>> This patchset was tested by running the libhugetlbfs testsuite with 64KB >>> and 2MB pages on both architectures (on a 4KB base page size arm64 kernel). >>> >>> [1] https://lore.kernel.org/linux-arm-kernel/20240215103205.2607016-1-ryan.roberts@arm.com/ >>> >>> Changes in v2: >>> - Rebase on top of 6.9-rc3 >>> >>> Alexandre Ghiti (9): >>> riscv: Restore the pfn in a NAPOT pte when manipulated by core mm code >>> riscv: Safely remove huge_pte_offset() when manipulating NAPOT ptes >>> mm: Use common huge_ptep_get() function for riscv/arm64 >>> mm: Use common set_huge_pte_at() function for riscv/arm64 >>> mm: Use common huge_pte_clear() function for riscv/arm64 >>> mm: Use common huge_ptep_get_and_clear() function for riscv/arm64 >>> mm: Use common huge_ptep_set_access_flags() function for riscv/arm64 >>> mm: Use common huge_ptep_set_wrprotect() function for riscv/arm64 >>> mm: Use common huge_ptep_clear_flush() function for riscv/arm64 >>> >>> arch/arm64/Kconfig | 1 + >>> arch/arm64/include/asm/pgtable.h | 56 +++++- >>> arch/arm64/mm/hugetlbpage.c | 291 +--------------------------- >>> arch/riscv/Kconfig | 1 + >>> arch/riscv/include/asm/hugetlb.h | 2 +- >>> arch/riscv/include/asm/pgtable-64.h | 11 ++ >>> arch/riscv/include/asm/pgtable.h | 153 +++++++++++++-- >>> arch/riscv/mm/hugetlbpage.c | 227 ---------------------- >>> arch/riscv/mm/pgtable.c | 6 +- >>> mm/Kconfig | 3 + >>> mm/Makefile | 1 + >>> mm/contpte.c | 272 ++++++++++++++++++++++++++ >>> 12 files changed, 480 insertions(+), 544 deletions(-) >>> create mode 100644 mm/contpte.c >>> >>
Hi Ryan, On 12/05/2024 19:25, Alexandre Ghiti wrote: > Hi Ryan, > > On Fri, May 10, 2024 at 3:49 PM Ryan Roberts <ryan.roberts@arm.com> wrote: >> On 08/05/2024 12:34, Alexandre Ghiti wrote: >>> This patchset intends to merge the contiguous ptes hugetlbfs implementation >>> of arm64 and riscv. >>> >>> Both arm64 and riscv support the use of contiguous ptes to map pages that >>> are larger than the default page table size, respectively called contpte >>> and svnapot. >>> >>> The riscv implementation differs from the arm64's in that the LSBs of the >>> pfn of a svnapot pte are used to store the size of the mapping, allowing >>> for future sizes to be added (for now only 64KB is supported). That's an >>> issue for the core mm code which expects to find the *real* pfn a pte points >>> to. Patch 1 fixes that by always returning svnapot ptes with the real pfn >>> and restores the size of the mapping when it is written to a page table. >>> >>> The following patches are just merges of the 2 different implementations >>> that currently exist in arm64 and riscv which are very similar. It paves >>> the way to the reuse of the recent contpte THP work by Ryan [1] to avoid >>> reimplementing the same in riscv. >> Hi Alexandre, >> >> I've skimmed through this series and the one that moves contpte. I can see there >> is definitely value in sharing the implementation, and the rough shape of things >> seems appropriate. I had some minor concerns about making it harder to implement >> potential future arm64 errata workarounds but on reflection, most of the >> now-shared code is really just wrapping the primitives that are still arch-specific. >> >> I'm going to need to spend proper time reviewing it to give detailed feedback, >> but I'll be out on paternity leave for 3 weeks from end of Monday at the latest. > Too bad, I expected to discuss that with you at LSF/MM...But congrats! > Hope your wife is fine :) > >> So realistically I won't be able to do the detailed review until at least the >> first week of June. >> >> Some high level thoughts: >> >> - huge_ptep_* functions could be working on different sized huge ptes - arm64 >> supports contpte, pmd, contpmd and pud. Is keeping them in contpte.c >> appropriate? > Hmm indeed, I'll see what I can do. So I took a look at that. It amounts to doing the same as what we do for THP contptes, ie having both contpte-aware and "normal" APIs. Let's take for example huge_ptep_get(), below is what I get. To me it's not that bad, so I'll implement this unless there is strong opposition. diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index f8efbc128446..869a9aae6c68 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1715,6 +1715,16 @@ static inline void clear_young_dirty_ptes(struct vm_area_struct *vma, contpte_clear_young_dirty_ptes(vma, addr, ptep, nr, flags); } +static inline pte_t huge_ptep_get(pte_t *ptep) +{ + pte_t orig_pte = __ptep_get(ptep); + + if (!pte_present(orig_pte) || !pte_cont(orig_pte)) + return orig_pte; + + return contpte_huge_ptep_get(ptep); +} + #else /* CONFIG_ARM64_CONTPTE */ #define ptep_get __ptep_get @@ -1736,6 +1746,8 @@ static inline void clear_young_dirty_ptes(struct vm_area_struct *vma, #define ptep_set_access_flags __ptep_set_access_flags #define clear_young_dirty_ptes __clear_young_dirty_ptes +#define huge_ptep_get __ptep_get + #endif /* CONFIG_ARM64_CONTPTE */ #endif /* !__ASSEMBLY__ */ diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c index 3f09ac73cce3..aa0ee3f02226 100644 --- a/arch/arm64/mm/hugetlbpage.c +++ b/arch/arm64/mm/hugetlbpage.c @@ -127,28 +127,6 @@ static inline int num_contig_ptes(unsigned long size, size_t *pgsize) return contig_ptes; } -pte_t huge_ptep_get(pte_t *ptep) -{ - int ncontig, i; - size_t pgsize; - pte_t orig_pte = __ptep_get(ptep); - - if (!pte_present(orig_pte) || !pte_cont(orig_pte)) - return orig_pte; - - ncontig = num_contig_ptes(page_size(pte_page(orig_pte)), &pgsize); - for (i = 0; i < ncontig; i++, ptep++) { - pte_t pte = __ptep_get(ptep); - - if (pte_dirty(pte)) - orig_pte = pte_mkdirty(orig_pte); - - if (pte_young(pte)) - orig_pte = pte_mkyoung(orig_pte); - } - return orig_pte; -} - /* * Changing some bits of contiguous entries requires us to follow a * Break-Before-Make approach, breaking the whole contiguous set diff --git a/mm/contpte.c b/mm/contpte.c new file mode 100644 index 000000000000..4e742cf00b6f --- /dev/null +++ b/mm/contpte.c @@ -0,0 +1,17 @@ +pte_t contpte_huge_ptep_get(pte_t *ptep) +{ + int ncontig, i; + size_t pgsize; + + ncontig = num_contig_ptes(page_size(pte_page(orig_pte)), &pgsize); + for (i = 0; i < ncontig; i++, ptep++) { + pte_t pte = __ptep_get(ptep); + + if (pte_dirty(pte)) + orig_pte = pte_mkdirty(orig_pte); + + if (pte_young(pte)) + orig_pte = pte_mkyoung(orig_pte); + } + return orig_pte; +} > >> Perhaps it's better to keep huge_pte and contpte separate? Also, it >> only works on arm64 because we can get away with calling the lower-level pte >> functions even when the huge_pte is actually a contpmd/pmd/pud, because the >> format is the same. That might present challenges to other arches if the format >> is different? > Yes, but I think that if that happens, we could get away with it by > choosing the right function depending on the size of the mapping? > >> - It might be easier to review if the arm64 stuff is first moved (without >> changes) then modified to make it suitable for riscv, then for riscv to be >> hooked up. At the moment I'm trying to follow all 3 parts per-function. > Ok, let me give it a try during your paternity leave! > >> Thanks, >> Ryan > Thanks, > > Alex > >> >>> This patchset was tested by running the libhugetlbfs testsuite with 64KB >>> and 2MB pages on both architectures (on a 4KB base page size arm64 kernel). >>> >>> [1] https://lore.kernel.org/linux-arm-kernel/20240215103205.2607016-1-ryan.roberts@arm.com/ >>> >>> Changes in v2: >>> - Rebase on top of 6.9-rc3 >>> >>> Alexandre Ghiti (9): >>> riscv: Restore the pfn in a NAPOT pte when manipulated by core mm code >>> riscv: Safely remove huge_pte_offset() when manipulating NAPOT ptes >>> mm: Use common huge_ptep_get() function for riscv/arm64 >>> mm: Use common set_huge_pte_at() function for riscv/arm64 >>> mm: Use common huge_pte_clear() function for riscv/arm64 >>> mm: Use common huge_ptep_get_and_clear() function for riscv/arm64 >>> mm: Use common huge_ptep_set_access_flags() function for riscv/arm64 >>> mm: Use common huge_ptep_set_wrprotect() function for riscv/arm64 >>> mm: Use common huge_ptep_clear_flush() function for riscv/arm64 >>> >>> arch/arm64/Kconfig | 1 + >>> arch/arm64/include/asm/pgtable.h | 56 +++++- >>> arch/arm64/mm/hugetlbpage.c | 291 +--------------------------- >>> arch/riscv/Kconfig | 1 + >>> arch/riscv/include/asm/hugetlb.h | 2 +- >>> arch/riscv/include/asm/pgtable-64.h | 11 ++ >>> arch/riscv/include/asm/pgtable.h | 153 +++++++++++++-- >>> arch/riscv/mm/hugetlbpage.c | 227 ---------------------- >>> arch/riscv/mm/pgtable.c | 6 +- >>> mm/Kconfig | 3 + >>> mm/Makefile | 1 + >>> mm/contpte.c | 272 ++++++++++++++++++++++++++ >>> 12 files changed, 480 insertions(+), 544 deletions(-) >>> create mode 100644 mm/contpte.c >>> > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv