From: Alistair Popple <apopple@nvidia.com> To: akpm@linux-foundation.org, linux-mm@kvack.org Cc: Felix.Kuehling@amd.com, rcampbell@nvidia.com, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, hch@lst.de, jgg@nvidia.com, jglisse@redhat.com, willy@infradead.org, alex.sierra@amd.com, jhubbard@nvidia.com, Alistair Popple <apopple@nvidia.com> Subject: [PATCH v2 2/3] mm/gup.c: Migrate device coherent pages when pinning instead of failing Date: Mon, 7 Feb 2022 15:26:47 +1100 [thread overview] Message-ID: <dd9960b327ca49a9103d9f97868ea7b0b81186c4.1644207242.git-series.apopple@nvidia.com> (raw) In-Reply-To: <cover.0d3c846b1c6c294e055ff7ebe221fab9964c1436.1644207242.git-series.apopple@nvidia.com> Currently any attempts to pin a device coherent page will fail. This is because device coherent pages need to be managed by a device driver, and pinning them would prevent a driver from migrating them off the device. However this is no reason to fail pinning of these pages. These are coherent and accessible from the CPU so can be migrated just like pinning ZONE_MOVABLE pages. So instead of failing all attempts to pin them first try migrating them out of ZONE_DEVICE. Signed-off-by: Alistair Popple <apopple@nvidia.com> Acked-by: Felix Kuehling <Felix.Kuehling@amd.com> --- Changes for v2: - Added Felix's Acked-by - Fixed missing check for dpage == NULL mm/gup.c | 105 ++++++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 95 insertions(+), 10 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 56d9577..5e826db 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1861,6 +1861,60 @@ struct page *get_dump_page(unsigned long addr) #ifdef CONFIG_MIGRATION /* + * Migrates a device coherent page back to normal memory. Caller should have a + * reference on page which will be copied to the new page if migration is + * successful or dropped on failure. + */ +static struct page *migrate_device_page(struct page *page, + unsigned int gup_flags) +{ + struct page *dpage; + struct migrate_vma args; + unsigned long src_pfn, dst_pfn = 0; + + lock_page(page); + src_pfn = migrate_pfn(page_to_pfn(page)) | MIGRATE_PFN_MIGRATE; + args.src = &src_pfn; + args.dst = &dst_pfn; + args.cpages = 1; + args.npages = 1; + args.vma = NULL; + migrate_vma_setup(&args); + if (!(src_pfn & MIGRATE_PFN_MIGRATE)) + return NULL; + + dpage = alloc_pages(GFP_USER | __GFP_NOWARN, 0); + + /* + * get/pin the new page now so we don't have to retry gup after + * migrating. We already have a reference so this should never fail. + */ + if (dpage && WARN_ON_ONCE(!try_grab_page(dpage, gup_flags))) { + __free_pages(dpage, 0); + dpage = NULL; + } + + if (dpage) { + lock_page(dpage); + dst_pfn = migrate_pfn(page_to_pfn(dpage)); + } + + migrate_vma_pages(&args); + if (src_pfn & MIGRATE_PFN_MIGRATE) + copy_highpage(dpage, page); + migrate_vma_finalize(&args); + if (dpage && !(src_pfn & MIGRATE_PFN_MIGRATE)) { + if (gup_flags & FOLL_PIN) + unpin_user_page(dpage); + else + put_page(dpage); + dpage = NULL; + } + + return dpage; +} + +/* * Check whether all pages are pinnable, if so return number of pages. If some * pages are not pinnable, migrate them, and unpin all pages. Return zero if * pages were migrated, or if some pages were not successfully isolated. @@ -1888,15 +1942,40 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages, continue; prev_head = head; /* - * If we get a movable page, since we are going to be pinning - * these entries, try to move them out if possible. + * Device coherent pages are managed by a driver and should not + * be pinned indefinitely as it prevents the driver moving the + * page. So when trying to pin with FOLL_LONGTERM instead try + * migrating page out of device memory. */ if (is_dev_private_or_coherent_page(head)) { + /* + * device private pages will get faulted in during gup + * so it shouldn't be possible to see one here. + */ WARN_ON_ONCE(is_device_private_page(head)); - ret = -EFAULT; - goto unpin_pages; + WARN_ON_ONCE(PageCompound(head)); + + /* + * migration will fail if the page is pinned, so convert + * the pin on the source page to a normal reference. + */ + if (gup_flags & FOLL_PIN) { + get_page(head); + unpin_user_page(head); + } + + pages[i] = migrate_device_page(head, gup_flags); + if (!pages[i]) { + ret = -EBUSY; + break; + } + continue; } + /* + * If we get a movable page, since we are going to be pinning + * these entries, try to move them out if possible. + */ if (!is_pinnable_page(head)) { if (PageHuge(head)) { if (!isolate_huge_page(head, &movable_page_list)) @@ -1924,16 +2003,22 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages, * If list is empty, and no isolation errors, means that all pages are * in the correct zone. */ - if (list_empty(&movable_page_list) && !isolation_error_count) + if (!ret && list_empty(&movable_page_list) && !isolation_error_count) return nr_pages; -unpin_pages: - if (gup_flags & FOLL_PIN) { - unpin_user_pages(pages, nr_pages); - } else { - for (i = 0; i < nr_pages; i++) + for (i = 0; i < nr_pages; i++) + if (!pages[i]) + continue; + else if (gup_flags & FOLL_PIN) + unpin_user_page(pages[i]); + else put_page(pages[i]); + + if (ret && !list_empty(&movable_page_list)) { + putback_movable_pages(&movable_page_list); + return ret; } + if (!list_empty(&movable_page_list)) { ret = migrate_pages(&movable_page_list, alloc_migration_target, NULL, (unsigned long)&mtc, MIGRATE_SYNC, -- git-series 0.9.1
WARNING: multiple messages have this Message-ID (diff)
From: Alistair Popple <apopple@nvidia.com> To: akpm@linux-foundation.org, linux-mm@kvack.org Cc: alex.sierra@amd.com, rcampbell@nvidia.com, willy@infradead.org, jhubbard@nvidia.com, Felix.Kuehling@amd.com, Alistair Popple <apopple@nvidia.com>, dri-devel@lists.freedesktop.org, linux-xfs@vger.kernel.org, jglisse@redhat.com, amd-gfx@lists.freedesktop.org, jgg@nvidia.com, linux-ext4@vger.kernel.org, hch@lst.de Subject: [PATCH v2 2/3] mm/gup.c: Migrate device coherent pages when pinning instead of failing Date: Mon, 7 Feb 2022 15:26:47 +1100 [thread overview] Message-ID: <dd9960b327ca49a9103d9f97868ea7b0b81186c4.1644207242.git-series.apopple@nvidia.com> (raw) In-Reply-To: <cover.0d3c846b1c6c294e055ff7ebe221fab9964c1436.1644207242.git-series.apopple@nvidia.com> Currently any attempts to pin a device coherent page will fail. This is because device coherent pages need to be managed by a device driver, and pinning them would prevent a driver from migrating them off the device. However this is no reason to fail pinning of these pages. These are coherent and accessible from the CPU so can be migrated just like pinning ZONE_MOVABLE pages. So instead of failing all attempts to pin them first try migrating them out of ZONE_DEVICE. Signed-off-by: Alistair Popple <apopple@nvidia.com> Acked-by: Felix Kuehling <Felix.Kuehling@amd.com> --- Changes for v2: - Added Felix's Acked-by - Fixed missing check for dpage == NULL mm/gup.c | 105 ++++++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 95 insertions(+), 10 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 56d9577..5e826db 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1861,6 +1861,60 @@ struct page *get_dump_page(unsigned long addr) #ifdef CONFIG_MIGRATION /* + * Migrates a device coherent page back to normal memory. Caller should have a + * reference on page which will be copied to the new page if migration is + * successful or dropped on failure. + */ +static struct page *migrate_device_page(struct page *page, + unsigned int gup_flags) +{ + struct page *dpage; + struct migrate_vma args; + unsigned long src_pfn, dst_pfn = 0; + + lock_page(page); + src_pfn = migrate_pfn(page_to_pfn(page)) | MIGRATE_PFN_MIGRATE; + args.src = &src_pfn; + args.dst = &dst_pfn; + args.cpages = 1; + args.npages = 1; + args.vma = NULL; + migrate_vma_setup(&args); + if (!(src_pfn & MIGRATE_PFN_MIGRATE)) + return NULL; + + dpage = alloc_pages(GFP_USER | __GFP_NOWARN, 0); + + /* + * get/pin the new page now so we don't have to retry gup after + * migrating. We already have a reference so this should never fail. + */ + if (dpage && WARN_ON_ONCE(!try_grab_page(dpage, gup_flags))) { + __free_pages(dpage, 0); + dpage = NULL; + } + + if (dpage) { + lock_page(dpage); + dst_pfn = migrate_pfn(page_to_pfn(dpage)); + } + + migrate_vma_pages(&args); + if (src_pfn & MIGRATE_PFN_MIGRATE) + copy_highpage(dpage, page); + migrate_vma_finalize(&args); + if (dpage && !(src_pfn & MIGRATE_PFN_MIGRATE)) { + if (gup_flags & FOLL_PIN) + unpin_user_page(dpage); + else + put_page(dpage); + dpage = NULL; + } + + return dpage; +} + +/* * Check whether all pages are pinnable, if so return number of pages. If some * pages are not pinnable, migrate them, and unpin all pages. Return zero if * pages were migrated, or if some pages were not successfully isolated. @@ -1888,15 +1942,40 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages, continue; prev_head = head; /* - * If we get a movable page, since we are going to be pinning - * these entries, try to move them out if possible. + * Device coherent pages are managed by a driver and should not + * be pinned indefinitely as it prevents the driver moving the + * page. So when trying to pin with FOLL_LONGTERM instead try + * migrating page out of device memory. */ if (is_dev_private_or_coherent_page(head)) { + /* + * device private pages will get faulted in during gup + * so it shouldn't be possible to see one here. + */ WARN_ON_ONCE(is_device_private_page(head)); - ret = -EFAULT; - goto unpin_pages; + WARN_ON_ONCE(PageCompound(head)); + + /* + * migration will fail if the page is pinned, so convert + * the pin on the source page to a normal reference. + */ + if (gup_flags & FOLL_PIN) { + get_page(head); + unpin_user_page(head); + } + + pages[i] = migrate_device_page(head, gup_flags); + if (!pages[i]) { + ret = -EBUSY; + break; + } + continue; } + /* + * If we get a movable page, since we are going to be pinning + * these entries, try to move them out if possible. + */ if (!is_pinnable_page(head)) { if (PageHuge(head)) { if (!isolate_huge_page(head, &movable_page_list)) @@ -1924,16 +2003,22 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages, * If list is empty, and no isolation errors, means that all pages are * in the correct zone. */ - if (list_empty(&movable_page_list) && !isolation_error_count) + if (!ret && list_empty(&movable_page_list) && !isolation_error_count) return nr_pages; -unpin_pages: - if (gup_flags & FOLL_PIN) { - unpin_user_pages(pages, nr_pages); - } else { - for (i = 0; i < nr_pages; i++) + for (i = 0; i < nr_pages; i++) + if (!pages[i]) + continue; + else if (gup_flags & FOLL_PIN) + unpin_user_page(pages[i]); + else put_page(pages[i]); + + if (ret && !list_empty(&movable_page_list)) { + putback_movable_pages(&movable_page_list); + return ret; } + if (!list_empty(&movable_page_list)) { ret = migrate_pages(&movable_page_list, alloc_migration_target, NULL, (unsigned long)&mtc, MIGRATE_SYNC, -- git-series 0.9.1
next prev parent reply other threads:[~2022-02-07 6:17 UTC|newest] Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-02-07 4:26 [PATCH v2 0/3] Migrate device coherent pages on get_user_pages() Alistair Popple 2022-02-07 4:26 ` Alistair Popple 2022-02-07 4:26 ` [PATCH v2 1/3] migrate.c: Remove vma check in migrate_vma_setup() Alistair Popple 2022-02-07 4:26 ` Alistair Popple 2022-02-15 21:50 ` John Hubbard 2022-02-15 21:50 ` John Hubbard 2022-02-07 4:26 ` Alistair Popple [this message] 2022-02-07 4:26 ` [PATCH v2 2/3] mm/gup.c: Migrate device coherent pages when pinning instead of failing Alistair Popple 2022-02-10 10:53 ` David Hildenbrand 2022-02-10 10:53 ` David Hildenbrand 2022-02-10 11:39 ` Alistair Popple 2022-02-10 11:39 ` Alistair Popple 2022-02-10 11:47 ` David Hildenbrand 2022-02-10 11:47 ` David Hildenbrand 2022-02-10 23:41 ` Alistair Popple 2022-02-10 23:41 ` Alistair Popple 2022-02-15 12:03 ` David Hildenbrand 2022-02-15 12:03 ` David Hildenbrand 2022-02-12 2:10 ` John Hubbard 2022-02-12 2:10 ` John Hubbard 2022-02-12 2:51 ` Alistair Popple 2022-02-12 2:51 ` Alistair Popple 2022-02-12 3:04 ` John Hubbard 2022-02-12 3:04 ` John Hubbard 2022-02-14 0:05 ` Alistair Popple 2022-02-14 0:05 ` Alistair Popple 2022-02-07 4:26 ` [PATCH v2 3/3] tools: add hmm gup test for long term pinned device pages Alistair Popple 2022-02-07 4:26 ` Alistair Popple
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