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charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20190813145029.GA32451@hpe.com> User-Agent: Mutt/1.5.24 (2015-08-30) Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Aug 13, 2019 at 09:50:29AM -0500, Dimitri Sivanich wrote: > Bharath, >=20 > I do not believe that __get_user_pages_fast will work for the atomic ca= se, as > there is no guarantee that the 'current->mm' will be the correct one fo= r the > process in question, as the process might have moved away from the cpu = that is > handling interrupts for it's context. So what your saying is, there may be cases where current->mm !=3D gts->ts= _mm right? __get_user_pages_fast and get_user_pages do assume current->mm. These changes were inspired a bit from kvm. In kvm/kvm_main.c, hva_to_pfn_fast uses __get_user_pages_fast. THe comment above the function states it runs in atomic context. Just curious, get_user_pages also uses current->mm. Do you think that is also an issue?=20 Do you feel using get_user_pages_remote would be a better idea? We can specify the mm_struct in get_user_pages_remote? Thank you Bharath > On Sat, Aug 10, 2019 at 01:08:17AM +0530, Bharath Vedartham wrote: > > For pages that were retained via get_user_pages*(), release those pag= es > > via the new put_user_page*() routines, instead of via put_page() or > > release_pages(). > >=20 > > This is part a tree-wide conversion, as described in commit fc1d8e7cc= a2d > > ("mm: introduce put_user_page*(), placeholder versions"). > >=20 > > As part of this conversion, the *pte_lookup functions can be removed = and > > be easily replaced with get_user_pages_fast() functions. In the case = of > > atomic lookup, __get_user_pages_fast() is used, because it does not f= all > > back to the slow path: get_user_pages(). get_user_pages_fast(), on th= e other > > hand, first calls __get_user_pages_fast(), but then falls back to the > > slow path if __get_user_pages_fast() fails. > >=20 > > Also: remove unnecessary CONFIG_HUGETLB ifdefs. > >=20 > > Cc: Ira Weiny > > Cc: John Hubbard > > Cc: J=E9r=F4me Glisse > > Cc: Greg Kroah-Hartman > > Cc: Dimitri Sivanich > > Cc: Arnd Bergmann > > Cc: William Kucharski > > Cc: Christoph Hellwig > > Cc: linux-kernel@vger.kernel.org > > Cc: linux-mm@kvack.org > > Cc: linux-kernel-mentees@lists.linuxfoundation.org > > Reviewed-by: Ira Weiny > > Reviewed-by: John Hubbard > > Reviewed-by: William Kucharski > > Signed-off-by: Bharath Vedartham > > --- > > This is a fold of the 3 patches in the v2 patch series. > > The review tags were given to the individual patches. > >=20 > > Changes since v3 > > - Used gup flags in get_user_pages_fast rather than > > boolean flags. > > Changes since v4 > > - Updated changelog according to John Hubbard. > > --- > > drivers/misc/sgi-gru/grufault.c | 112 +++++++++---------------------= ---------- > > 1 file changed, 24 insertions(+), 88 deletions(-) > >=20 > > diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/g= rufault.c > > index 4b713a8..304e9c5 100644 > > --- a/drivers/misc/sgi-gru/grufault.c > > +++ b/drivers/misc/sgi-gru/grufault.c > > @@ -166,96 +166,20 @@ static void get_clear_fault_map(struct gru_stat= e *gru, > > } > > =20 > > /* > > - * Atomic (interrupt context) & non-atomic (user context) functions = to > > - * convert a vaddr into a physical address. The size of the page > > - * is returned in pageshift. > > - * returns: > > - * 0 - successful > > - * < 0 - error code > > - * 1 - (atomic only) try again in non-atomic context > > - */ > > -static int non_atomic_pte_lookup(struct vm_area_struct *vma, > > - unsigned long vaddr, int write, > > - unsigned long *paddr, int *pageshift) > > -{ > > - struct page *page; > > - > > -#ifdef CONFIG_HUGETLB_PAGE > > - *pageshift =3D is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > > -#else > > - *pageshift =3D PAGE_SHIFT; > > -#endif > > - if (get_user_pages(vaddr, 1, write ? FOLL_WRITE : 0, &page, NULL) <= =3D 0) > > - return -EFAULT; > > - *paddr =3D page_to_phys(page); > > - put_page(page); > > - return 0; > > -} > > - > > -/* > > - * atomic_pte_lookup > > + * mmap_sem is already helod on entry to this function. This guarant= ees > > + * existence of the page tables. > > * > > - * Convert a user virtual address to a physical address > > * Only supports Intel large pages (2MB only) on x86_64. > > - * ZZZ - hugepage support is incomplete > > - * > > - * NOTE: mmap_sem is already held on entry to this function. This > > - * guarantees existence of the page tables. > > + * ZZZ - hugepage support is incomplete. > > */ > > -static int atomic_pte_lookup(struct vm_area_struct *vma, unsigned lo= ng vaddr, > > - int write, unsigned long *paddr, int *pageshift) > > -{ > > - pgd_t *pgdp; > > - p4d_t *p4dp; > > - pud_t *pudp; > > - pmd_t *pmdp; > > - pte_t pte; > > - > > - pgdp =3D pgd_offset(vma->vm_mm, vaddr); > > - if (unlikely(pgd_none(*pgdp))) > > - goto err; > > - > > - p4dp =3D p4d_offset(pgdp, vaddr); > > - if (unlikely(p4d_none(*p4dp))) > > - goto err; > > - > > - pudp =3D pud_offset(p4dp, vaddr); > > - if (unlikely(pud_none(*pudp))) > > - goto err; > > - > > - pmdp =3D pmd_offset(pudp, vaddr); > > - if (unlikely(pmd_none(*pmdp))) > > - goto err; > > -#ifdef CONFIG_X86_64 > > - if (unlikely(pmd_large(*pmdp))) > > - pte =3D *(pte_t *) pmdp; > > - else > > -#endif > > - pte =3D *pte_offset_kernel(pmdp, vaddr); > > - > > - if (unlikely(!pte_present(pte) || > > - (write && (!pte_write(pte) || !pte_dirty(pte))))) > > - return 1; > > - > > - *paddr =3D pte_pfn(pte) << PAGE_SHIFT; > > -#ifdef CONFIG_HUGETLB_PAGE > > - *pageshift =3D is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > > -#else > > - *pageshift =3D PAGE_SHIFT; > > -#endif > > - return 0; > > - > > -err: > > - return 1; > > -} > > - > > static int gru_vtop(struct gru_thread_state *gts, unsigned long vadd= r, > > int write, int atomic, unsigned long *gpa, int *pageshift) > > { > > struct mm_struct *mm =3D gts->ts_mm; > > struct vm_area_struct *vma; > > unsigned long paddr; > > - int ret, ps; > > + int ret; > > + struct page *page; > > =20 > > vma =3D find_vma(mm, vaddr); > > if (!vma) > > @@ -263,21 +187,33 @@ static int gru_vtop(struct gru_thread_state *gt= s, unsigned long vaddr, > > =20 > > /* > > * Atomic lookup is faster & usually works even if called in non-at= omic > > - * context. > > + * context. get_user_pages_fast does atomic lookup before falling b= ack to > > + * slow gup. > > */ > > rmb(); /* Must/check ms_range_active before loading PTEs */ > > - ret =3D atomic_pte_lookup(vma, vaddr, write, &paddr, &ps); > > - if (ret) { > > - if (atomic) > > + if (atomic) { > > + ret =3D __get_user_pages_fast(vaddr, 1, write, &page); > > + if (!ret) > > goto upm; > > - if (non_atomic_pte_lookup(vma, vaddr, write, &paddr, &ps)) > > + } else { > > + ret =3D get_user_pages_fast(vaddr, 1, write ? FOLL_WRITE : 0, &pag= e); > > + if (!ret) > > goto inval; > > } > > + > > + paddr =3D page_to_phys(page); > > + put_user_page(page); > > + > > + if (unlikely(is_vm_hugetlb_page(vma))) > > + *pageshift =3D HPAGE_SHIFT; > > + else > > + *pageshift =3D PAGE_SHIFT; > > + > > if (is_gru_paddr(paddr)) > > goto inval; > > - paddr =3D paddr & ~((1UL << ps) - 1); > > + paddr =3D paddr & ~((1UL << *pageshift) - 1); > > *gpa =3D uv_soc_phys_ram_to_gpa(paddr); > > - *pageshift =3D ps; > > + > > return VTOP_SUCCESS; > > =20 > > inval: > > --=20 > > 2.7.4 > >=20