* [Linux-kernel-mentees][PATCH v5 0/1] get_user_pages changes @ 2019-08-09 19:38 Bharath Vedartham 2019-08-09 19:38 ` [Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*() Bharath Vedartham 0 siblings, 1 reply; 10+ messages in thread From: Bharath Vedartham @ 2019-08-09 19:38 UTC (permalink / raw) To: jhubbard, gregkh, sivanich, arnd Cc: ira.weiny, jglisse, william.kucharski, hch, linux-kernel, linux-mm, linux-kernel-mentees, Bharath Vedartham In this 5th version of the patch series, I have compressed the patches of the v2 patch series into one patch. This was suggested by Christoph Hellwig. The suggestion was to remove the pte_lookup functions and use the get_user_pages* functions directly instead of the pte_lookup functions. There is nothing different in this series compared to the v2 series, It essentially compresses the 3 patches of the original series into one patch. This series survives a compile test. Bharath Vedartham (1): sgi-gru: Remove *pte_lookup functions drivers/misc/sgi-gru/grufault.c | 112 +++++++++------------------------------- 1 file changed, 24 insertions(+), 88 deletions(-) -- 2.7.4 ^ permalink raw reply [flat|nested] 10+ messages in thread
* [Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*() 2019-08-09 19:38 [Linux-kernel-mentees][PATCH v5 0/1] get_user_pages changes Bharath Vedartham @ 2019-08-09 19:38 ` Bharath Vedartham 2019-08-13 14:50 ` Dimitri Sivanich 2019-08-18 17:58 ` Bharath Vedartham 0 siblings, 2 replies; 10+ messages in thread From: Bharath Vedartham @ 2019-08-09 19:38 UTC (permalink / raw) To: jhubbard, gregkh, sivanich, arnd Cc: ira.weiny, jglisse, william.kucharski, hch, linux-kernel, linux-mm, linux-kernel-mentees, Bharath Vedartham For pages that were retained via get_user_pages*(), release those pages via the new put_user_page*() routines, instead of via put_page() or release_pages(). This is part a tree-wide conversion, as described in commit fc1d8e7cca2d ("mm: introduce put_user_page*(), placeholder versions"). 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 fall back to the slow path: get_user_pages(). get_user_pages_fast(), on the other hand, first calls __get_user_pages_fast(), but then falls back to the slow path if __get_user_pages_fast() fails. Also: remove unnecessary CONFIG_HUGETLB ifdefs. Cc: Ira Weiny <ira.weiny@intel.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Jérôme Glisse <jglisse@redhat.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Dimitri Sivanich <sivanich@sgi.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: William Kucharski <william.kucharski@oracle.com> Cc: Christoph Hellwig <hch@lst.de> Cc: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org Cc: linux-kernel-mentees@lists.linuxfoundation.org Reviewed-by: Ira Weiny <ira.weiny@intel.com> Reviewed-by: John Hubbard <jhubbard@nvidia.com> Reviewed-by: William Kucharski <william.kucharski@oracle.com> Signed-off-by: Bharath Vedartham <linux.bhar@gmail.com> --- This is a fold of the 3 patches in the v2 patch series. The review tags were given to the individual patches. 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(-) diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.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_state *gru, } /* - * 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 = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; -#else - *pageshift = PAGE_SHIFT; -#endif - if (get_user_pages(vaddr, 1, write ? FOLL_WRITE : 0, &page, NULL) <= 0) - return -EFAULT; - *paddr = page_to_phys(page); - put_page(page); - return 0; -} - -/* - * atomic_pte_lookup + * mmap_sem is already helod on entry to this function. This guarantees + * 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 long vaddr, - int write, unsigned long *paddr, int *pageshift) -{ - pgd_t *pgdp; - p4d_t *p4dp; - pud_t *pudp; - pmd_t *pmdp; - pte_t pte; - - pgdp = pgd_offset(vma->vm_mm, vaddr); - if (unlikely(pgd_none(*pgdp))) - goto err; - - p4dp = p4d_offset(pgdp, vaddr); - if (unlikely(p4d_none(*p4dp))) - goto err; - - pudp = pud_offset(p4dp, vaddr); - if (unlikely(pud_none(*pudp))) - goto err; - - pmdp = pmd_offset(pudp, vaddr); - if (unlikely(pmd_none(*pmdp))) - goto err; -#ifdef CONFIG_X86_64 - if (unlikely(pmd_large(*pmdp))) - pte = *(pte_t *) pmdp; - else -#endif - pte = *pte_offset_kernel(pmdp, vaddr); - - if (unlikely(!pte_present(pte) || - (write && (!pte_write(pte) || !pte_dirty(pte))))) - return 1; - - *paddr = pte_pfn(pte) << PAGE_SHIFT; -#ifdef CONFIG_HUGETLB_PAGE - *pageshift = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; -#else - *pageshift = PAGE_SHIFT; -#endif - return 0; - -err: - return 1; -} - static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, int write, int atomic, unsigned long *gpa, int *pageshift) { struct mm_struct *mm = gts->ts_mm; struct vm_area_struct *vma; unsigned long paddr; - int ret, ps; + int ret; + struct page *page; vma = find_vma(mm, vaddr); if (!vma) @@ -263,21 +187,33 @@ static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, /* * Atomic lookup is faster & usually works even if called in non-atomic - * context. + * context. get_user_pages_fast does atomic lookup before falling back to + * slow gup. */ rmb(); /* Must/check ms_range_active before loading PTEs */ - ret = atomic_pte_lookup(vma, vaddr, write, &paddr, &ps); - if (ret) { - if (atomic) + if (atomic) { + ret = __get_user_pages_fast(vaddr, 1, write, &page); + if (!ret) goto upm; - if (non_atomic_pte_lookup(vma, vaddr, write, &paddr, &ps)) + } else { + ret = get_user_pages_fast(vaddr, 1, write ? FOLL_WRITE : 0, &page); + if (!ret) goto inval; } + + paddr = page_to_phys(page); + put_user_page(page); + + if (unlikely(is_vm_hugetlb_page(vma))) + *pageshift = HPAGE_SHIFT; + else + *pageshift = PAGE_SHIFT; + if (is_gru_paddr(paddr)) goto inval; - paddr = paddr & ~((1UL << ps) - 1); + paddr = paddr & ~((1UL << *pageshift) - 1); *gpa = uv_soc_phys_ram_to_gpa(paddr); - *pageshift = ps; + return VTOP_SUCCESS; inval: -- 2.7.4 ^ permalink raw reply related [flat|nested] 10+ messages in thread
* Re: [Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*() 2019-08-09 19:38 ` [Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*() Bharath Vedartham @ 2019-08-13 14:50 ` Dimitri Sivanich 2019-08-13 17:23 ` Bharath Vedartham 2019-08-18 17:58 ` Bharath Vedartham 1 sibling, 1 reply; 10+ messages in thread From: Dimitri Sivanich @ 2019-08-13 14:50 UTC (permalink / raw) To: Bharath Vedartham Cc: jhubbard, gregkh, sivanich, arnd, ira.weiny, jglisse, william.kucharski, hch, linux-kernel, linux-mm, linux-kernel-mentees Bharath, I do not believe that __get_user_pages_fast will work for the atomic case, as there is no guarantee that the 'current->mm' will be the correct one for the process in question, as the process might have moved away from the cpu that is handling interrupts for it's context. On Sat, Aug 10, 2019 at 01:08:17AM +0530, Bharath Vedartham wrote: > For pages that were retained via get_user_pages*(), release those pages > via the new put_user_page*() routines, instead of via put_page() or > release_pages(). > > This is part a tree-wide conversion, as described in commit fc1d8e7cca2d > ("mm: introduce put_user_page*(), placeholder versions"). > > 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 fall > back to the slow path: get_user_pages(). get_user_pages_fast(), on the other > hand, first calls __get_user_pages_fast(), but then falls back to the > slow path if __get_user_pages_fast() fails. > > Also: remove unnecessary CONFIG_HUGETLB ifdefs. > > Cc: Ira Weiny <ira.weiny@intel.com> > Cc: John Hubbard <jhubbard@nvidia.com> > Cc: Jérôme Glisse <jglisse@redhat.com> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: Dimitri Sivanich <sivanich@sgi.com> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: William Kucharski <william.kucharski@oracle.com> > Cc: Christoph Hellwig <hch@lst.de> > Cc: linux-kernel@vger.kernel.org > Cc: linux-mm@kvack.org > Cc: linux-kernel-mentees@lists.linuxfoundation.org > Reviewed-by: Ira Weiny <ira.weiny@intel.com> > Reviewed-by: John Hubbard <jhubbard@nvidia.com> > Reviewed-by: William Kucharski <william.kucharski@oracle.com> > Signed-off-by: Bharath Vedartham <linux.bhar@gmail.com> > --- > This is a fold of the 3 patches in the v2 patch series. > The review tags were given to the individual patches. > > 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(-) > > diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.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_state *gru, > } > > /* > - * 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 = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > -#else > - *pageshift = PAGE_SHIFT; > -#endif > - if (get_user_pages(vaddr, 1, write ? FOLL_WRITE : 0, &page, NULL) <= 0) > - return -EFAULT; > - *paddr = page_to_phys(page); > - put_page(page); > - return 0; > -} > - > -/* > - * atomic_pte_lookup > + * mmap_sem is already helod on entry to this function. This guarantees > + * 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 long vaddr, > - int write, unsigned long *paddr, int *pageshift) > -{ > - pgd_t *pgdp; > - p4d_t *p4dp; > - pud_t *pudp; > - pmd_t *pmdp; > - pte_t pte; > - > - pgdp = pgd_offset(vma->vm_mm, vaddr); > - if (unlikely(pgd_none(*pgdp))) > - goto err; > - > - p4dp = p4d_offset(pgdp, vaddr); > - if (unlikely(p4d_none(*p4dp))) > - goto err; > - > - pudp = pud_offset(p4dp, vaddr); > - if (unlikely(pud_none(*pudp))) > - goto err; > - > - pmdp = pmd_offset(pudp, vaddr); > - if (unlikely(pmd_none(*pmdp))) > - goto err; > -#ifdef CONFIG_X86_64 > - if (unlikely(pmd_large(*pmdp))) > - pte = *(pte_t *) pmdp; > - else > -#endif > - pte = *pte_offset_kernel(pmdp, vaddr); > - > - if (unlikely(!pte_present(pte) || > - (write && (!pte_write(pte) || !pte_dirty(pte))))) > - return 1; > - > - *paddr = pte_pfn(pte) << PAGE_SHIFT; > -#ifdef CONFIG_HUGETLB_PAGE > - *pageshift = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > -#else > - *pageshift = PAGE_SHIFT; > -#endif > - return 0; > - > -err: > - return 1; > -} > - > static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, > int write, int atomic, unsigned long *gpa, int *pageshift) > { > struct mm_struct *mm = gts->ts_mm; > struct vm_area_struct *vma; > unsigned long paddr; > - int ret, ps; > + int ret; > + struct page *page; > > vma = find_vma(mm, vaddr); > if (!vma) > @@ -263,21 +187,33 @@ static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, > > /* > * Atomic lookup is faster & usually works even if called in non-atomic > - * context. > + * context. get_user_pages_fast does atomic lookup before falling back to > + * slow gup. > */ > rmb(); /* Must/check ms_range_active before loading PTEs */ > - ret = atomic_pte_lookup(vma, vaddr, write, &paddr, &ps); > - if (ret) { > - if (atomic) > + if (atomic) { > + ret = __get_user_pages_fast(vaddr, 1, write, &page); > + if (!ret) > goto upm; > - if (non_atomic_pte_lookup(vma, vaddr, write, &paddr, &ps)) > + } else { > + ret = get_user_pages_fast(vaddr, 1, write ? FOLL_WRITE : 0, &page); > + if (!ret) > goto inval; > } > + > + paddr = page_to_phys(page); > + put_user_page(page); > + > + if (unlikely(is_vm_hugetlb_page(vma))) > + *pageshift = HPAGE_SHIFT; > + else > + *pageshift = PAGE_SHIFT; > + > if (is_gru_paddr(paddr)) > goto inval; > - paddr = paddr & ~((1UL << ps) - 1); > + paddr = paddr & ~((1UL << *pageshift) - 1); > *gpa = uv_soc_phys_ram_to_gpa(paddr); > - *pageshift = ps; > + > return VTOP_SUCCESS; > > inval: > -- > 2.7.4 > ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*() 2019-08-13 14:50 ` Dimitri Sivanich @ 2019-08-13 17:23 ` Bharath Vedartham 2019-08-13 18:19 ` Dimitri Sivanich 0 siblings, 1 reply; 10+ messages in thread From: Bharath Vedartham @ 2019-08-13 17:23 UTC (permalink / raw) To: Dimitri Sivanich Cc: jhubbard, gregkh, arnd, ira.weiny, jglisse, william.kucharski, hch, linux-kernel, linux-mm, linux-kernel-mentees On Tue, Aug 13, 2019 at 09:50:29AM -0500, Dimitri Sivanich wrote: > Bharath, > > I do not believe that __get_user_pages_fast will work for the atomic case, as > there is no guarantee that the 'current->mm' will be the correct one for 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 != 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? 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 pages > > via the new put_user_page*() routines, instead of via put_page() or > > release_pages(). > > > > This is part a tree-wide conversion, as described in commit fc1d8e7cca2d > > ("mm: introduce put_user_page*(), placeholder versions"). > > > > 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 fall > > back to the slow path: get_user_pages(). get_user_pages_fast(), on the other > > hand, first calls __get_user_pages_fast(), but then falls back to the > > slow path if __get_user_pages_fast() fails. > > > > Also: remove unnecessary CONFIG_HUGETLB ifdefs. > > > > Cc: Ira Weiny <ira.weiny@intel.com> > > Cc: John Hubbard <jhubbard@nvidia.com> > > Cc: Jérôme Glisse <jglisse@redhat.com> > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > Cc: Dimitri Sivanich <sivanich@sgi.com> > > Cc: Arnd Bergmann <arnd@arndb.de> > > Cc: William Kucharski <william.kucharski@oracle.com> > > Cc: Christoph Hellwig <hch@lst.de> > > Cc: linux-kernel@vger.kernel.org > > Cc: linux-mm@kvack.org > > Cc: linux-kernel-mentees@lists.linuxfoundation.org > > Reviewed-by: Ira Weiny <ira.weiny@intel.com> > > Reviewed-by: John Hubbard <jhubbard@nvidia.com> > > Reviewed-by: William Kucharski <william.kucharski@oracle.com> > > Signed-off-by: Bharath Vedartham <linux.bhar@gmail.com> > > --- > > This is a fold of the 3 patches in the v2 patch series. > > The review tags were given to the individual patches. > > > > 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(-) > > > > diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.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_state *gru, > > } > > > > /* > > - * 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 = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > > -#else > > - *pageshift = PAGE_SHIFT; > > -#endif > > - if (get_user_pages(vaddr, 1, write ? FOLL_WRITE : 0, &page, NULL) <= 0) > > - return -EFAULT; > > - *paddr = page_to_phys(page); > > - put_page(page); > > - return 0; > > -} > > - > > -/* > > - * atomic_pte_lookup > > + * mmap_sem is already helod on entry to this function. This guarantees > > + * 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 long vaddr, > > - int write, unsigned long *paddr, int *pageshift) > > -{ > > - pgd_t *pgdp; > > - p4d_t *p4dp; > > - pud_t *pudp; > > - pmd_t *pmdp; > > - pte_t pte; > > - > > - pgdp = pgd_offset(vma->vm_mm, vaddr); > > - if (unlikely(pgd_none(*pgdp))) > > - goto err; > > - > > - p4dp = p4d_offset(pgdp, vaddr); > > - if (unlikely(p4d_none(*p4dp))) > > - goto err; > > - > > - pudp = pud_offset(p4dp, vaddr); > > - if (unlikely(pud_none(*pudp))) > > - goto err; > > - > > - pmdp = pmd_offset(pudp, vaddr); > > - if (unlikely(pmd_none(*pmdp))) > > - goto err; > > -#ifdef CONFIG_X86_64 > > - if (unlikely(pmd_large(*pmdp))) > > - pte = *(pte_t *) pmdp; > > - else > > -#endif > > - pte = *pte_offset_kernel(pmdp, vaddr); > > - > > - if (unlikely(!pte_present(pte) || > > - (write && (!pte_write(pte) || !pte_dirty(pte))))) > > - return 1; > > - > > - *paddr = pte_pfn(pte) << PAGE_SHIFT; > > -#ifdef CONFIG_HUGETLB_PAGE > > - *pageshift = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > > -#else > > - *pageshift = PAGE_SHIFT; > > -#endif > > - return 0; > > - > > -err: > > - return 1; > > -} > > - > > static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, > > int write, int atomic, unsigned long *gpa, int *pageshift) > > { > > struct mm_struct *mm = gts->ts_mm; > > struct vm_area_struct *vma; > > unsigned long paddr; > > - int ret, ps; > > + int ret; > > + struct page *page; > > > > vma = find_vma(mm, vaddr); > > if (!vma) > > @@ -263,21 +187,33 @@ static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, > > > > /* > > * Atomic lookup is faster & usually works even if called in non-atomic > > - * context. > > + * context. get_user_pages_fast does atomic lookup before falling back to > > + * slow gup. > > */ > > rmb(); /* Must/check ms_range_active before loading PTEs */ > > - ret = atomic_pte_lookup(vma, vaddr, write, &paddr, &ps); > > - if (ret) { > > - if (atomic) > > + if (atomic) { > > + ret = __get_user_pages_fast(vaddr, 1, write, &page); > > + if (!ret) > > goto upm; > > - if (non_atomic_pte_lookup(vma, vaddr, write, &paddr, &ps)) > > + } else { > > + ret = get_user_pages_fast(vaddr, 1, write ? FOLL_WRITE : 0, &page); > > + if (!ret) > > goto inval; > > } > > + > > + paddr = page_to_phys(page); > > + put_user_page(page); > > + > > + if (unlikely(is_vm_hugetlb_page(vma))) > > + *pageshift = HPAGE_SHIFT; > > + else > > + *pageshift = PAGE_SHIFT; > > + > > if (is_gru_paddr(paddr)) > > goto inval; > > - paddr = paddr & ~((1UL << ps) - 1); > > + paddr = paddr & ~((1UL << *pageshift) - 1); > > *gpa = uv_soc_phys_ram_to_gpa(paddr); > > - *pageshift = ps; > > + > > return VTOP_SUCCESS; > > > > inval: > > -- > > 2.7.4 > > ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*() 2019-08-13 17:23 ` Bharath Vedartham @ 2019-08-13 18:19 ` Dimitri Sivanich 2019-08-14 17:30 ` Bharath Vedartham 0 siblings, 1 reply; 10+ messages in thread From: Dimitri Sivanich @ 2019-08-13 18:19 UTC (permalink / raw) To: Bharath Vedartham Cc: jhubbard, gregkh, arnd, ira.weiny, jglisse, william.kucharski, hch, linux-kernel, linux-mm, linux-kernel-mentees, sivanich On Tue, Aug 13, 2019 at 10:53:01PM +0530, Bharath Vedartham wrote: > On Tue, Aug 13, 2019 at 09:50:29AM -0500, Dimitri Sivanich wrote: > > Bharath, > > > > I do not believe that __get_user_pages_fast will work for the atomic case, as > > there is no guarantee that the 'current->mm' will be the correct one for 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 != gts->ts_mm > right? __get_user_pages_fast and get_user_pages do assume current->mm. Correct, in the case of atomic context. > > 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? Not in non-atomic context. Notice that it is currently done that way. > > Do you feel using get_user_pages_remote would be a better idea? We can > specify the mm_struct in get_user_pages_remote? From that standpoint maybe, but is it safe in interrupt context? > > 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 pages > > > via the new put_user_page*() routines, instead of via put_page() or > > > release_pages(). > > > > > > This is part a tree-wide conversion, as described in commit fc1d8e7cca2d > > > ("mm: introduce put_user_page*(), placeholder versions"). > > > > > > 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 fall > > > back to the slow path: get_user_pages(). get_user_pages_fast(), on the other > > > hand, first calls __get_user_pages_fast(), but then falls back to the > > > slow path if __get_user_pages_fast() fails. > > > > > > Also: remove unnecessary CONFIG_HUGETLB ifdefs. > > > > > > Cc: Ira Weiny <ira.weiny@intel.com> > > > Cc: John Hubbard <jhubbard@nvidia.com> > > > Cc: Jérôme Glisse <jglisse@redhat.com> > > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > > Cc: Dimitri Sivanich <sivanich@sgi.com> > > > Cc: Arnd Bergmann <arnd@arndb.de> > > > Cc: William Kucharski <william.kucharski@oracle.com> > > > Cc: Christoph Hellwig <hch@lst.de> > > > Cc: linux-kernel@vger.kernel.org > > > Cc: linux-mm@kvack.org > > > Cc: linux-kernel-mentees@lists.linuxfoundation.org > > > Reviewed-by: Ira Weiny <ira.weiny@intel.com> > > > Reviewed-by: John Hubbard <jhubbard@nvidia.com> > > > Reviewed-by: William Kucharski <william.kucharski@oracle.com> > > > Signed-off-by: Bharath Vedartham <linux.bhar@gmail.com> > > > --- > > > This is a fold of the 3 patches in the v2 patch series. > > > The review tags were given to the individual patches. > > > > > > 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(-) > > > > > > diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.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_state *gru, > > > } > > > > > > /* > > > - * 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 = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > > > -#else > > > - *pageshift = PAGE_SHIFT; > > > -#endif > > > - if (get_user_pages(vaddr, 1, write ? FOLL_WRITE : 0, &page, NULL) <= 0) > > > - return -EFAULT; > > > - *paddr = page_to_phys(page); > > > - put_page(page); > > > - return 0; > > > -} > > > - > > > -/* > > > - * atomic_pte_lookup > > > + * mmap_sem is already helod on entry to this function. This guarantees > > > + * 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 long vaddr, > > > - int write, unsigned long *paddr, int *pageshift) > > > -{ > > > - pgd_t *pgdp; > > > - p4d_t *p4dp; > > > - pud_t *pudp; > > > - pmd_t *pmdp; > > > - pte_t pte; > > > - > > > - pgdp = pgd_offset(vma->vm_mm, vaddr); > > > - if (unlikely(pgd_none(*pgdp))) > > > - goto err; > > > - > > > - p4dp = p4d_offset(pgdp, vaddr); > > > - if (unlikely(p4d_none(*p4dp))) > > > - goto err; > > > - > > > - pudp = pud_offset(p4dp, vaddr); > > > - if (unlikely(pud_none(*pudp))) > > > - goto err; > > > - > > > - pmdp = pmd_offset(pudp, vaddr); > > > - if (unlikely(pmd_none(*pmdp))) > > > - goto err; > > > -#ifdef CONFIG_X86_64 > > > - if (unlikely(pmd_large(*pmdp))) > > > - pte = *(pte_t *) pmdp; > > > - else > > > -#endif > > > - pte = *pte_offset_kernel(pmdp, vaddr); > > > - > > > - if (unlikely(!pte_present(pte) || > > > - (write && (!pte_write(pte) || !pte_dirty(pte))))) > > > - return 1; > > > - > > > - *paddr = pte_pfn(pte) << PAGE_SHIFT; > > > -#ifdef CONFIG_HUGETLB_PAGE > > > - *pageshift = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > > > -#else > > > - *pageshift = PAGE_SHIFT; > > > -#endif > > > - return 0; > > > - > > > -err: > > > - return 1; > > > -} > > > - > > > static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, > > > int write, int atomic, unsigned long *gpa, int *pageshift) > > > { > > > struct mm_struct *mm = gts->ts_mm; > > > struct vm_area_struct *vma; > > > unsigned long paddr; > > > - int ret, ps; > > > + int ret; > > > + struct page *page; > > > > > > vma = find_vma(mm, vaddr); > > > if (!vma) > > > @@ -263,21 +187,33 @@ static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, > > > > > > /* > > > * Atomic lookup is faster & usually works even if called in non-atomic > > > - * context. > > > + * context. get_user_pages_fast does atomic lookup before falling back to > > > + * slow gup. > > > */ > > > rmb(); /* Must/check ms_range_active before loading PTEs */ > > > - ret = atomic_pte_lookup(vma, vaddr, write, &paddr, &ps); > > > - if (ret) { > > > - if (atomic) > > > + if (atomic) { > > > + ret = __get_user_pages_fast(vaddr, 1, write, &page); > > > + if (!ret) > > > goto upm; > > > - if (non_atomic_pte_lookup(vma, vaddr, write, &paddr, &ps)) > > > + } else { > > > + ret = get_user_pages_fast(vaddr, 1, write ? FOLL_WRITE : 0, &page); > > > + if (!ret) > > > goto inval; > > > } > > > + > > > + paddr = page_to_phys(page); > > > + put_user_page(page); > > > + > > > + if (unlikely(is_vm_hugetlb_page(vma))) > > > + *pageshift = HPAGE_SHIFT; > > > + else > > > + *pageshift = PAGE_SHIFT; > > > + > > > if (is_gru_paddr(paddr)) > > > goto inval; > > > - paddr = paddr & ~((1UL << ps) - 1); > > > + paddr = paddr & ~((1UL << *pageshift) - 1); > > > *gpa = uv_soc_phys_ram_to_gpa(paddr); > > > - *pageshift = ps; > > > + > > > return VTOP_SUCCESS; > > > > > > inval: > > > -- > > > 2.7.4 > > > ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*() 2019-08-13 18:19 ` Dimitri Sivanich @ 2019-08-14 17:30 ` Bharath Vedartham 2019-08-14 17:38 ` Jason Gunthorpe 0 siblings, 1 reply; 10+ messages in thread From: Bharath Vedartham @ 2019-08-14 17:30 UTC (permalink / raw) To: Dimitri Sivanich Cc: jhubbard, gregkh, arnd, ira.weiny, jglisse, william.kucharski, hch, linux-kernel, linux-mm, linux-kernel-mentees On Tue, Aug 13, 2019 at 01:19:38PM -0500, Dimitri Sivanich wrote: > On Tue, Aug 13, 2019 at 10:53:01PM +0530, Bharath Vedartham wrote: > > On Tue, Aug 13, 2019 at 09:50:29AM -0500, Dimitri Sivanich wrote: > > > Bharath, > > > > > > I do not believe that __get_user_pages_fast will work for the atomic case, as > > > there is no guarantee that the 'current->mm' will be the correct one for 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 != gts->ts_mm > > right? __get_user_pages_fast and get_user_pages do assume current->mm. > > Correct, in the case of atomic context. > > > > > 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? > > Not in non-atomic context. Notice that it is currently done that way. > > > > > Do you feel using get_user_pages_remote would be a better idea? We can > > specify the mm_struct in get_user_pages_remote? > > From that standpoint maybe, but is it safe in interrupt context? Hmm.. The gup maintainers seemed fine with the code.. Now this is only an issue if gru_vtop can be executed in an interrupt context. get_user_pages_remote is not valid in an interrupt context(if CONFIG_MMU is set). If we follow the function, in __get_user_pages, cond_resched() is called which definitly confirms that we can't run this function in an interrupt context. I think we might need some advice from the gup maintainers here. Note that the comment on the function __get_user_pages_fast states that __get_user_pages_fast is IRQ-safe. Thank you Bharath > > > > 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 pages > > > > via the new put_user_page*() routines, instead of via put_page() or > > > > release_pages(). > > > > > > > > This is part a tree-wide conversion, as described in commit fc1d8e7cca2d > > > > ("mm: introduce put_user_page*(), placeholder versions"). > > > > > > > > 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 fall > > > > back to the slow path: get_user_pages(). get_user_pages_fast(), on the other > > > > hand, first calls __get_user_pages_fast(), but then falls back to the > > > > slow path if __get_user_pages_fast() fails. > > > > > > > > Also: remove unnecessary CONFIG_HUGETLB ifdefs. > > > > > > > > Cc: Ira Weiny <ira.weiny@intel.com> > > > > Cc: John Hubbard <jhubbard@nvidia.com> > > > > Cc: Jérôme Glisse <jglisse@redhat.com> > > > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > > > Cc: Dimitri Sivanich <sivanich@sgi.com> > > > > Cc: Arnd Bergmann <arnd@arndb.de> > > > > Cc: William Kucharski <william.kucharski@oracle.com> > > > > Cc: Christoph Hellwig <hch@lst.de> > > > > Cc: linux-kernel@vger.kernel.org > > > > Cc: linux-mm@kvack.org > > > > Cc: linux-kernel-mentees@lists.linuxfoundation.org > > > > Reviewed-by: Ira Weiny <ira.weiny@intel.com> > > > > Reviewed-by: John Hubbard <jhubbard@nvidia.com> > > > > Reviewed-by: William Kucharski <william.kucharski@oracle.com> > > > > Signed-off-by: Bharath Vedartham <linux.bhar@gmail.com> > > > > --- > > > > This is a fold of the 3 patches in the v2 patch series. > > > > The review tags were given to the individual patches. > > > > > > > > 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(-) > > > > > > > > diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.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_state *gru, > > > > } > > > > > > > > /* > > > > - * 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 = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > > > > -#else > > > > - *pageshift = PAGE_SHIFT; > > > > -#endif > > > > - if (get_user_pages(vaddr, 1, write ? FOLL_WRITE : 0, &page, NULL) <= 0) > > > > - return -EFAULT; > > > > - *paddr = page_to_phys(page); > > > > - put_page(page); > > > > - return 0; > > > > -} > > > > - > > > > -/* > > > > - * atomic_pte_lookup > > > > + * mmap_sem is already helod on entry to this function. This guarantees > > > > + * 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 long vaddr, > > > > - int write, unsigned long *paddr, int *pageshift) > > > > -{ > > > > - pgd_t *pgdp; > > > > - p4d_t *p4dp; > > > > - pud_t *pudp; > > > > - pmd_t *pmdp; > > > > - pte_t pte; > > > > - > > > > - pgdp = pgd_offset(vma->vm_mm, vaddr); > > > > - if (unlikely(pgd_none(*pgdp))) > > > > - goto err; > > > > - > > > > - p4dp = p4d_offset(pgdp, vaddr); > > > > - if (unlikely(p4d_none(*p4dp))) > > > > - goto err; > > > > - > > > > - pudp = pud_offset(p4dp, vaddr); > > > > - if (unlikely(pud_none(*pudp))) > > > > - goto err; > > > > - > > > > - pmdp = pmd_offset(pudp, vaddr); > > > > - if (unlikely(pmd_none(*pmdp))) > > > > - goto err; > > > > -#ifdef CONFIG_X86_64 > > > > - if (unlikely(pmd_large(*pmdp))) > > > > - pte = *(pte_t *) pmdp; > > > > - else > > > > -#endif > > > > - pte = *pte_offset_kernel(pmdp, vaddr); > > > > - > > > > - if (unlikely(!pte_present(pte) || > > > > - (write && (!pte_write(pte) || !pte_dirty(pte))))) > > > > - return 1; > > > > - > > > > - *paddr = pte_pfn(pte) << PAGE_SHIFT; > > > > -#ifdef CONFIG_HUGETLB_PAGE > > > > - *pageshift = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > > > > -#else > > > > - *pageshift = PAGE_SHIFT; > > > > -#endif > > > > - return 0; > > > > - > > > > -err: > > > > - return 1; > > > > -} > > > > - > > > > static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, > > > > int write, int atomic, unsigned long *gpa, int *pageshift) > > > > { > > > > struct mm_struct *mm = gts->ts_mm; > > > > struct vm_area_struct *vma; > > > > unsigned long paddr; > > > > - int ret, ps; > > > > + int ret; > > > > + struct page *page; > > > > > > > > vma = find_vma(mm, vaddr); > > > > if (!vma) > > > > @@ -263,21 +187,33 @@ static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, > > > > > > > > /* > > > > * Atomic lookup is faster & usually works even if called in non-atomic > > > > - * context. > > > > + * context. get_user_pages_fast does atomic lookup before falling back to > > > > + * slow gup. > > > > */ > > > > rmb(); /* Must/check ms_range_active before loading PTEs */ > > > > - ret = atomic_pte_lookup(vma, vaddr, write, &paddr, &ps); > > > > - if (ret) { > > > > - if (atomic) > > > > + if (atomic) { > > > > + ret = __get_user_pages_fast(vaddr, 1, write, &page); > > > > + if (!ret) > > > > goto upm; > > > > - if (non_atomic_pte_lookup(vma, vaddr, write, &paddr, &ps)) > > > > + } else { > > > > + ret = get_user_pages_fast(vaddr, 1, write ? FOLL_WRITE : 0, &page); > > > > + if (!ret) > > > > goto inval; > > > > } > > > > + > > > > + paddr = page_to_phys(page); > > > > + put_user_page(page); > > > > + > > > > + if (unlikely(is_vm_hugetlb_page(vma))) > > > > + *pageshift = HPAGE_SHIFT; > > > > + else > > > > + *pageshift = PAGE_SHIFT; > > > > + > > > > if (is_gru_paddr(paddr)) > > > > goto inval; > > > > - paddr = paddr & ~((1UL << ps) - 1); > > > > + paddr = paddr & ~((1UL << *pageshift) - 1); > > > > *gpa = uv_soc_phys_ram_to_gpa(paddr); > > > > - *pageshift = ps; > > > > + > > > > return VTOP_SUCCESS; > > > > > > > > inval: > > > > -- > > > > 2.7.4 > > > > ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*() 2019-08-14 17:30 ` Bharath Vedartham @ 2019-08-14 17:38 ` Jason Gunthorpe 2019-08-14 18:00 ` Bharath Vedartham 0 siblings, 1 reply; 10+ messages in thread From: Jason Gunthorpe @ 2019-08-14 17:38 UTC (permalink / raw) To: Bharath Vedartham Cc: Dimitri Sivanich, jhubbard, gregkh, arnd, ira.weiny, jglisse, william.kucharski, hch, linux-kernel, linux-mm, linux-kernel-mentees On Wed, Aug 14, 2019 at 11:00:34PM +0530, Bharath Vedartham wrote: > On Tue, Aug 13, 2019 at 01:19:38PM -0500, Dimitri Sivanich wrote: > > On Tue, Aug 13, 2019 at 10:53:01PM +0530, Bharath Vedartham wrote: > > > On Tue, Aug 13, 2019 at 09:50:29AM -0500, Dimitri Sivanich wrote: > > > > Bharath, > > > > > > > > I do not believe that __get_user_pages_fast will work for the atomic case, as > > > > there is no guarantee that the 'current->mm' will be the correct one for 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 != gts->ts_mm > > > right? __get_user_pages_fast and get_user_pages do assume current->mm. > > > > Correct, in the case of atomic context. > > > > > > > > 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? > > > > Not in non-atomic context. Notice that it is currently done that way. > > > > > > > > Do you feel using get_user_pages_remote would be a better idea? We can > > > specify the mm_struct in get_user_pages_remote? > > > > From that standpoint maybe, but is it safe in interrupt context? > Hmm.. The gup maintainers seemed fine with the code.. > > Now this is only an issue if gru_vtop can be executed in an interrupt > context. > > get_user_pages_remote is not valid in an interrupt context(if CONFIG_MMU > is set). If we follow the function, in __get_user_pages, cond_resched() > is called which definitly confirms that we can't run this function in an > interrupt context. > > I think we might need some advice from the gup maintainers here. > Note that the comment on the function __get_user_pages_fast states that > __get_user_pages_fast is IRQ-safe. vhost is doing some approach where they switch current to the target then call __get_user_pages_fast in an IRQ context, that might be a reasonable pattern If this is a regular occurance we should probably add a get_atomic_user_pages_remote() to make the pattern clear. Jason ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*() 2019-08-14 17:38 ` Jason Gunthorpe @ 2019-08-14 18:00 ` Bharath Vedartham 0 siblings, 0 replies; 10+ messages in thread From: Bharath Vedartham @ 2019-08-14 18:00 UTC (permalink / raw) To: Jason Gunthorpe Cc: Dimitri Sivanich, jhubbard, gregkh, arnd, ira.weiny, jglisse, william.kucharski, hch, linux-kernel, linux-mm, linux-kernel-mentees On Wed, Aug 14, 2019 at 02:38:30PM -0300, Jason Gunthorpe wrote: > On Wed, Aug 14, 2019 at 11:00:34PM +0530, Bharath Vedartham wrote: > > On Tue, Aug 13, 2019 at 01:19:38PM -0500, Dimitri Sivanich wrote: > > > On Tue, Aug 13, 2019 at 10:53:01PM +0530, Bharath Vedartham wrote: > > > > On Tue, Aug 13, 2019 at 09:50:29AM -0500, Dimitri Sivanich wrote: > > > > > Bharath, > > > > > > > > > > I do not believe that __get_user_pages_fast will work for the atomic case, as > > > > > there is no guarantee that the 'current->mm' will be the correct one for 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 != gts->ts_mm > > > > right? __get_user_pages_fast and get_user_pages do assume current->mm. > > > > > > Correct, in the case of atomic context. > > > > > > > > > > > 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? > > > > > > Not in non-atomic context. Notice that it is currently done that way. > > > > > > > > > > > Do you feel using get_user_pages_remote would be a better idea? We can > > > > specify the mm_struct in get_user_pages_remote? > > > > > > From that standpoint maybe, but is it safe in interrupt context? > > Hmm.. The gup maintainers seemed fine with the code.. > > > > Now this is only an issue if gru_vtop can be executed in an interrupt > > context. > > > > get_user_pages_remote is not valid in an interrupt context(if CONFIG_MMU > > is set). If we follow the function, in __get_user_pages, cond_resched() > > is called which definitly confirms that we can't run this function in an > > interrupt context. > > > > I think we might need some advice from the gup maintainers here. > > Note that the comment on the function __get_user_pages_fast states that > > __get_user_pages_fast is IRQ-safe. > > vhost is doing some approach where they switch current to the target > then call __get_user_pages_fast in an IRQ context, that might be a > reasonable pattern > > If this is a regular occurance we should probably add a > get_atomic_user_pages_remote() to make the pattern clear. > > Jason That makes sense. get_atomic_user_pages_remote() should not be hard to write. AFAIKS __get_user_pages_fast is special_cased for current, we could probably just add a new parameter of the mm_struct to the page table walking code in gup.c But till then I think we can approach this by the way vhost approaches this problem by switching current to the target. Thank you Bharath ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*() 2019-08-09 19:38 ` [Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*() Bharath Vedartham 2019-08-13 14:50 ` Dimitri Sivanich @ 2019-08-18 17:58 ` Bharath Vedartham 2019-08-18 18:25 ` Dimitri Sivanich 1 sibling, 1 reply; 10+ messages in thread From: Bharath Vedartham @ 2019-08-18 17:58 UTC (permalink / raw) To: jhubbard, gregkh, sivanich, arnd Cc: ira.weiny, jglisse, william.kucharski, hch, linux-kernel, linux-mm, linux-kernel-mentees Hi Dimitri, Can you confirm that this driver will run gru_vtop() in interrupt context? If so, I ll send you another set of patches in which I don't change the *pte_lookup functions but only change put_page to put_user_page and remove the ifdef for CONFIG_HUGETLB_PAGE. Thank you for your time. 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 pages > via the new put_user_page*() routines, instead of via put_page() or > release_pages(). > > This is part a tree-wide conversion, as described in commit fc1d8e7cca2d > ("mm: introduce put_user_page*(), placeholder versions"). > > 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 fall > back to the slow path: get_user_pages(). get_user_pages_fast(), on the other > hand, first calls __get_user_pages_fast(), but then falls back to the > slow path if __get_user_pages_fast() fails. > > Also: remove unnecessary CONFIG_HUGETLB ifdefs. > > Cc: Ira Weiny <ira.weiny@intel.com> > Cc: John Hubbard <jhubbard@nvidia.com> > Cc: Jérôme Glisse <jglisse@redhat.com> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: Dimitri Sivanich <sivanich@sgi.com> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: William Kucharski <william.kucharski@oracle.com> > Cc: Christoph Hellwig <hch@lst.de> > Cc: linux-kernel@vger.kernel.org > Cc: linux-mm@kvack.org > Cc: linux-kernel-mentees@lists.linuxfoundation.org > Reviewed-by: Ira Weiny <ira.weiny@intel.com> > Reviewed-by: John Hubbard <jhubbard@nvidia.com> > Reviewed-by: William Kucharski <william.kucharski@oracle.com> > Signed-off-by: Bharath Vedartham <linux.bhar@gmail.com> > --- > This is a fold of the 3 patches in the v2 patch series. > The review tags were given to the individual patches. > > 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(-) > > diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.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_state *gru, > } > > /* > - * 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 = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > -#else > - *pageshift = PAGE_SHIFT; > -#endif > - if (get_user_pages(vaddr, 1, write ? FOLL_WRITE : 0, &page, NULL) <= 0) > - return -EFAULT; > - *paddr = page_to_phys(page); > - put_page(page); > - return 0; > -} > - > -/* > - * atomic_pte_lookup > + * mmap_sem is already helod on entry to this function. This guarantees > + * 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 long vaddr, > - int write, unsigned long *paddr, int *pageshift) > -{ > - pgd_t *pgdp; > - p4d_t *p4dp; > - pud_t *pudp; > - pmd_t *pmdp; > - pte_t pte; > - > - pgdp = pgd_offset(vma->vm_mm, vaddr); > - if (unlikely(pgd_none(*pgdp))) > - goto err; > - > - p4dp = p4d_offset(pgdp, vaddr); > - if (unlikely(p4d_none(*p4dp))) > - goto err; > - > - pudp = pud_offset(p4dp, vaddr); > - if (unlikely(pud_none(*pudp))) > - goto err; > - > - pmdp = pmd_offset(pudp, vaddr); > - if (unlikely(pmd_none(*pmdp))) > - goto err; > -#ifdef CONFIG_X86_64 > - if (unlikely(pmd_large(*pmdp))) > - pte = *(pte_t *) pmdp; > - else > -#endif > - pte = *pte_offset_kernel(pmdp, vaddr); > - > - if (unlikely(!pte_present(pte) || > - (write && (!pte_write(pte) || !pte_dirty(pte))))) > - return 1; > - > - *paddr = pte_pfn(pte) << PAGE_SHIFT; > -#ifdef CONFIG_HUGETLB_PAGE > - *pageshift = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > -#else > - *pageshift = PAGE_SHIFT; > -#endif > - return 0; > - > -err: > - return 1; > -} > - > static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, > int write, int atomic, unsigned long *gpa, int *pageshift) > { > struct mm_struct *mm = gts->ts_mm; > struct vm_area_struct *vma; > unsigned long paddr; > - int ret, ps; > + int ret; > + struct page *page; > > vma = find_vma(mm, vaddr); > if (!vma) > @@ -263,21 +187,33 @@ static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, > > /* > * Atomic lookup is faster & usually works even if called in non-atomic > - * context. > + * context. get_user_pages_fast does atomic lookup before falling back to > + * slow gup. > */ > rmb(); /* Must/check ms_range_active before loading PTEs */ > - ret = atomic_pte_lookup(vma, vaddr, write, &paddr, &ps); > - if (ret) { > - if (atomic) > + if (atomic) { > + ret = __get_user_pages_fast(vaddr, 1, write, &page); > + if (!ret) > goto upm; > - if (non_atomic_pte_lookup(vma, vaddr, write, &paddr, &ps)) > + } else { > + ret = get_user_pages_fast(vaddr, 1, write ? FOLL_WRITE : 0, &page); > + if (!ret) > goto inval; > } > + > + paddr = page_to_phys(page); > + put_user_page(page); > + > + if (unlikely(is_vm_hugetlb_page(vma))) > + *pageshift = HPAGE_SHIFT; > + else > + *pageshift = PAGE_SHIFT; > + > if (is_gru_paddr(paddr)) > goto inval; > - paddr = paddr & ~((1UL << ps) - 1); > + paddr = paddr & ~((1UL << *pageshift) - 1); > *gpa = uv_soc_phys_ram_to_gpa(paddr); > - *pageshift = ps; > + > return VTOP_SUCCESS; > > inval: > -- > 2.7.4 > ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*() 2019-08-18 17:58 ` Bharath Vedartham @ 2019-08-18 18:25 ` Dimitri Sivanich 0 siblings, 0 replies; 10+ messages in thread From: Dimitri Sivanich @ 2019-08-18 18:25 UTC (permalink / raw) To: Bharath Vedartham Cc: jhubbard, gregkh, sivanich, arnd, ira.weiny, jglisse, william.kucharski, hch, linux-kernel, linux-mm, linux-kernel-mentees Yes it will. On Sun, Aug 18, 2019 at 11:28:24PM +0530, Bharath Vedartham wrote: > Hi Dimitri, > > Can you confirm that this driver will run gru_vtop() in interrupt > context? > > If so, I ll send you another set of patches in which I don't change the > *pte_lookup functions but only change put_page to put_user_page and > remove the ifdef for CONFIG_HUGETLB_PAGE. > > Thank you for your time. > > 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 pages > > via the new put_user_page*() routines, instead of via put_page() or > > release_pages(). > > > > This is part a tree-wide conversion, as described in commit fc1d8e7cca2d > > ("mm: introduce put_user_page*(), placeholder versions"). > > > > 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 fall > > back to the slow path: get_user_pages(). get_user_pages_fast(), on the other > > hand, first calls __get_user_pages_fast(), but then falls back to the > > slow path if __get_user_pages_fast() fails. > > > > Also: remove unnecessary CONFIG_HUGETLB ifdefs. > > > > Cc: Ira Weiny <ira.weiny@intel.com> > > Cc: John Hubbard <jhubbard@nvidia.com> > > Cc: Jérôme Glisse <jglisse@redhat.com> > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > Cc: Dimitri Sivanich <sivanich@sgi.com> > > Cc: Arnd Bergmann <arnd@arndb.de> > > Cc: William Kucharski <william.kucharski@oracle.com> > > Cc: Christoph Hellwig <hch@lst.de> > > Cc: linux-kernel@vger.kernel.org > > Cc: linux-mm@kvack.org > > Cc: linux-kernel-mentees@lists.linuxfoundation.org > > Reviewed-by: Ira Weiny <ira.weiny@intel.com> > > Reviewed-by: John Hubbard <jhubbard@nvidia.com> > > Reviewed-by: William Kucharski <william.kucharski@oracle.com> > > Signed-off-by: Bharath Vedartham <linux.bhar@gmail.com> > > --- > > This is a fold of the 3 patches in the v2 patch series. > > The review tags were given to the individual patches. > > > > 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(-) > > > > diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.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_state *gru, > > } > > > > /* > > - * 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 = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > > -#else > > - *pageshift = PAGE_SHIFT; > > -#endif > > - if (get_user_pages(vaddr, 1, write ? FOLL_WRITE : 0, &page, NULL) <= 0) > > - return -EFAULT; > > - *paddr = page_to_phys(page); > > - put_page(page); > > - return 0; > > -} > > - > > -/* > > - * atomic_pte_lookup > > + * mmap_sem is already helod on entry to this function. This guarantees > > + * 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 long vaddr, > > - int write, unsigned long *paddr, int *pageshift) > > -{ > > - pgd_t *pgdp; > > - p4d_t *p4dp; > > - pud_t *pudp; > > - pmd_t *pmdp; > > - pte_t pte; > > - > > - pgdp = pgd_offset(vma->vm_mm, vaddr); > > - if (unlikely(pgd_none(*pgdp))) > > - goto err; > > - > > - p4dp = p4d_offset(pgdp, vaddr); > > - if (unlikely(p4d_none(*p4dp))) > > - goto err; > > - > > - pudp = pud_offset(p4dp, vaddr); > > - if (unlikely(pud_none(*pudp))) > > - goto err; > > - > > - pmdp = pmd_offset(pudp, vaddr); > > - if (unlikely(pmd_none(*pmdp))) > > - goto err; > > -#ifdef CONFIG_X86_64 > > - if (unlikely(pmd_large(*pmdp))) > > - pte = *(pte_t *) pmdp; > > - else > > -#endif > > - pte = *pte_offset_kernel(pmdp, vaddr); > > - > > - if (unlikely(!pte_present(pte) || > > - (write && (!pte_write(pte) || !pte_dirty(pte))))) > > - return 1; > > - > > - *paddr = pte_pfn(pte) << PAGE_SHIFT; > > -#ifdef CONFIG_HUGETLB_PAGE > > - *pageshift = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > > -#else > > - *pageshift = PAGE_SHIFT; > > -#endif > > - return 0; > > - > > -err: > > - return 1; > > -} > > - > > static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, > > int write, int atomic, unsigned long *gpa, int *pageshift) > > { > > struct mm_struct *mm = gts->ts_mm; > > struct vm_area_struct *vma; > > unsigned long paddr; > > - int ret, ps; > > + int ret; > > + struct page *page; > > > > vma = find_vma(mm, vaddr); > > if (!vma) > > @@ -263,21 +187,33 @@ static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, > > > > /* > > * Atomic lookup is faster & usually works even if called in non-atomic > > - * context. > > + * context. get_user_pages_fast does atomic lookup before falling back to > > + * slow gup. > > */ > > rmb(); /* Must/check ms_range_active before loading PTEs */ > > - ret = atomic_pte_lookup(vma, vaddr, write, &paddr, &ps); > > - if (ret) { > > - if (atomic) > > + if (atomic) { > > + ret = __get_user_pages_fast(vaddr, 1, write, &page); > > + if (!ret) > > goto upm; > > - if (non_atomic_pte_lookup(vma, vaddr, write, &paddr, &ps)) > > + } else { > > + ret = get_user_pages_fast(vaddr, 1, write ? FOLL_WRITE : 0, &page); > > + if (!ret) > > goto inval; > > } > > + > > + paddr = page_to_phys(page); > > + put_user_page(page); > > + > > + if (unlikely(is_vm_hugetlb_page(vma))) > > + *pageshift = HPAGE_SHIFT; > > + else > > + *pageshift = PAGE_SHIFT; > > + > > if (is_gru_paddr(paddr)) > > goto inval; > > - paddr = paddr & ~((1UL << ps) - 1); > > + paddr = paddr & ~((1UL << *pageshift) - 1); > > *gpa = uv_soc_phys_ram_to_gpa(paddr); > > - *pageshift = ps; > > + > > return VTOP_SUCCESS; > > > > inval: > > -- > > 2.7.4 > > ^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2019-08-18 18:26 UTC | newest] Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2019-08-09 19:38 [Linux-kernel-mentees][PATCH v5 0/1] get_user_pages changes Bharath Vedartham 2019-08-09 19:38 ` [Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*() Bharath Vedartham 2019-08-13 14:50 ` Dimitri Sivanich 2019-08-13 17:23 ` Bharath Vedartham 2019-08-13 18:19 ` Dimitri Sivanich 2019-08-14 17:30 ` Bharath Vedartham 2019-08-14 17:38 ` Jason Gunthorpe 2019-08-14 18:00 ` Bharath Vedartham 2019-08-18 17:58 ` Bharath Vedartham 2019-08-18 18:25 ` Dimitri Sivanich
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).