From: Dan Williams <dan.j.williams@intel.com>
To: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>, John Hubbard <jhubbard@nvidia.com>,
Ross Zwisler <ross.zwisler@linux.intel.com>
Subject: Re: [HMM v16 04/15] mm/ZONE_DEVICE/unaddressable: add support for un-addressable device memory v2
Date: Sun, 15 Jan 2017 23:05:43 -0800 [thread overview]
Message-ID: <CAPcyv4gnXyxHGitBCLbksy8PnHtePQ8260DKiF7CX8FXj2CtFQ@mail.gmail.com> (raw)
In-Reply-To: <1484238642-10674-5-git-send-email-jglisse@redhat.com>
On Thu, Jan 12, 2017 at 8:30 AM, Jérôme Glisse <jglisse@redhat.com> wrote:
> This add support for un-addressable device memory. Such memory is hotpluged
> only so we can have struct page but we should never map them as such memory
> can not be accessed by CPU. For that reason it uses a special swap entry for
> CPU page table entry.
>
> This patch implement all the logic from special swap type to handling CPU
> page fault through a callback specified in the ZONE_DEVICE pgmap struct.
>
> Architecture that wish to support un-addressable device memory should make
> sure to never populate the kernel linar mapping for the physical range.
>
> This feature potentially breaks memory hotplug unless every driver using it
> magically predicts the future addresses of where memory will be hotplugged.
>
> Changed since v1:
> - Add unaddressable memory resource descriptor enum
> - Explain why memory hotplug can fail because of un-addressable memory
How can we merge this with a known potential regression?
>
> Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
> ---
> drivers/dax/pmem.c | 4 +--
> drivers/nvdimm/pmem.c | 6 ++--
> fs/proc/task_mmu.c | 10 +++++-
> include/linux/ioport.h | 1 +
> include/linux/memory_hotplug.h | 7 ++++
> include/linux/memremap.h | 29 +++++++++++++++--
> include/linux/swap.h | 18 +++++++++--
> include/linux/swapops.h | 67 +++++++++++++++++++++++++++++++++++++++
> kernel/memremap.c | 43 +++++++++++++++++++++++--
> mm/Kconfig | 12 +++++++
> mm/memory.c | 64 ++++++++++++++++++++++++++++++++++++-
> mm/memory_hotplug.c | 10 ++++--
> mm/mprotect.c | 12 +++++++
> tools/testing/nvdimm/test/iomap.c | 3 +-
> 14 files changed, 269 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
> index 66af7b1..c50b58d 100644
> --- a/drivers/dax/pmem.c
> +++ b/drivers/dax/pmem.c
> @@ -111,8 +111,8 @@ static int dax_pmem_probe(struct device *dev)
> if (rc)
> return rc;
>
> - addr = devm_memremap_pages(dev, &res, &dax_pmem->ref,
> - altmap, NULL, NULL);
> + addr = devm_memremap_pages(dev, &res, &dax_pmem->ref, altmap,
> + NULL, NULL, NULL, NULL, MEMORY_DEVICE);
> if (IS_ERR(addr))
> return PTR_ERR(addr);
>
> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index f2f1904..8166a56 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -282,7 +282,8 @@ static int pmem_attach_disk(struct device *dev,
> pmem->pfn_flags = PFN_DEV;
> if (is_nd_pfn(dev)) {
> addr = devm_memremap_pages(dev, &pfn_res, &q->q_usage_counter,
> - altmap, NULL, NULL);
> + altmap, NULL, NULL, NULL,
> + NULL, MEMORY_DEVICE);
> pfn_sb = nd_pfn->pfn_sb;
> pmem->data_offset = le64_to_cpu(pfn_sb->dataoff);
> pmem->pfn_pad = resource_size(res) - resource_size(&pfn_res);
> @@ -292,7 +293,8 @@ static int pmem_attach_disk(struct device *dev,
> } else if (pmem_should_map_pages(dev)) {
> addr = devm_memremap_pages(dev, &nsio->res,
> &q->q_usage_counter,
> - NULL, NULL, NULL);
> + NULL, NULL, NULL, NULL,
> + NULL, MEMORY_DEVICE);
> pmem->pfn_flags |= PFN_MAP;
> } else
> addr = devm_memremap(dev, pmem->phys_addr,
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 958f325..9a6ab71 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -535,8 +535,11 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
> } else {
> mss->swap_pss += (u64)PAGE_SIZE << PSS_SHIFT;
> }
> - } else if (is_migration_entry(swpent))
> + } else if (is_migration_entry(swpent)) {
> page = migration_entry_to_page(swpent);
> + } else if (is_device_entry(swpent)) {
> + page = device_entry_to_page(swpent);
> + }
> } else if (unlikely(IS_ENABLED(CONFIG_SHMEM) && mss->check_shmem_swap
> && pte_none(*pte))) {
> page = find_get_entry(vma->vm_file->f_mapping,
> @@ -699,6 +702,8 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
>
> if (is_migration_entry(swpent))
> page = migration_entry_to_page(swpent);
> + if (is_device_entry(swpent))
> + page = device_entry_to_page(swpent);
> }
> if (page) {
> int mapcount = page_mapcount(page);
> @@ -1182,6 +1187,9 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
> flags |= PM_SWAP;
> if (is_migration_entry(entry))
> page = migration_entry_to_page(entry);
> +
> + if (is_device_entry(entry))
> + page = device_entry_to_page(entry);
> }
>
> if (page && !PageAnon(page))
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 6230064..d154a18 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -130,6 +130,7 @@ enum {
> IORES_DESC_ACPI_NV_STORAGE = 3,
> IORES_DESC_PERSISTENT_MEMORY = 4,
> IORES_DESC_PERSISTENT_MEMORY_LEGACY = 5,
> + IORES_DESC_UNADDRESSABLE_MEMORY = 6,
> };
>
> /* helpers to define resources */
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 3f50eb8..e7c5dc6 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -285,15 +285,22 @@ extern int zone_for_memory(int nid, u64 start, u64 size, int zone_default,
> * never relied on struct page migration so far and new user of might also
> * prefer avoiding struct page migration.
> *
> + * For device memory (which use ZONE_DEVICE) we want differentiate between CPU
> + * accessible memory (persitent memory, device memory on an architecture with a
> + * system bus that allow transparent access to device memory) and unaddressable
> + * memory (device memory that can not be accessed by CPU directly).
> + *
> * New non device memory specific flags can be added if ever needed.
> *
> * MEMORY_REGULAR: regular system memory
> * DEVICE_MEMORY: device memory create a ZONE_DEVICE zone for it
> * DEVICE_MEMORY_ALLOW_MIGRATE: page in that device memory ca be migrated
> + * MEMORY_DEVICE_UNADDRESSABLE: un-addressable memory (CPU can not access it)
> */
> #define MEMORY_NORMAL 0
> #define MEMORY_DEVICE (1 << 0)
> #define MEMORY_DEVICE_ALLOW_MIGRATE (1 << 1)
> +#define MEMORY_DEVICE_UNADDRESSABLE (1 << 2)
>
> extern int arch_add_memory(int nid, u64 start, u64 size, int flags);
> extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
> index 582561f..4b9f02c 100644
> --- a/include/linux/memremap.h
> +++ b/include/linux/memremap.h
> @@ -35,31 +35,42 @@ static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
> }
> #endif
>
> +typedef int (*dev_page_fault_t)(struct vm_area_struct *vma,
> + unsigned long addr,
> + struct page *page,
> + unsigned flags,
> + pmd_t *pmdp);
> typedef void (*dev_page_free_t)(struct page *page, void *data);
>
> /**
> * struct dev_pagemap - metadata for ZONE_DEVICE mappings
> + * @page_fault: callback when CPU fault on an un-addressable device page
> * @page_free: free page callback when page refcount reach 1
> * @altmap: pre-allocated/reserved memory for vmemmap allocations
> * @res: physical address range covered by @ref
> * @ref: reference count that pins the devm_memremap_pages() mapping
> * @dev: host device of the mapping for debug
> * @data: privata data pointer for page_free
> + * @flags: device memory flags (look for MEMORY_DEVICE_* memory_hotplug.h)
> */
> struct dev_pagemap {
> + dev_page_fault_t page_fault;
> dev_page_free_t page_free;
> struct vmem_altmap *altmap;
> const struct resource *res;
> struct percpu_ref *ref;
> struct device *dev;
> void *data;
> + int flags;
> };
dev_pagemap is only meant for get_user_pages() to do lookups of ptes
with _PAGE_DEVMAP and take a reference against the hosting device..
Why can't HMM use the typical vm_operations_struct fault path and push
more of these details to a driver rather than the core?
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-01-16 7:05 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-12 16:30 [HMM v16 00/16] HMM (Heterogeneous Memory Management) v16 Jérôme Glisse
2017-01-12 16:30 ` [HMM v16 01/15] mm/memory/hotplug: convert device bool to int to allow for more flags v2 Jérôme Glisse
2017-01-13 13:57 ` Balbir Singh
2017-01-13 14:45 ` Jerome Glisse
2017-01-12 16:30 ` [HMM v16 02/15] mm/ZONE_DEVICE/devmem_pages_remove: allow early removal of device memory v2 Jérôme Glisse
2017-01-12 16:30 ` [HMM v16 03/15] mm/ZONE_DEVICE/free-page: callback when page is freed Jérôme Glisse
2017-01-12 16:30 ` [HMM v16 04/15] mm/ZONE_DEVICE/unaddressable: add support for un-addressable device memory v2 Jérôme Glisse
2017-01-16 7:05 ` Dan Williams [this message]
2017-01-16 15:17 ` Jerome Glisse
2017-01-16 19:31 ` Dan Williams
2017-01-16 20:13 ` Jerome Glisse
2017-01-17 0:58 ` Dan Williams
2017-01-17 2:00 ` Jerome Glisse
2017-01-17 2:57 ` Dan Williams
2017-01-12 16:30 ` [HMM v16 05/15] mm/ZONE_DEVICE/x86: add support for un-addressable device memory Jérôme Glisse
2017-01-12 16:30 ` [HMM v16 06/15] mm/hmm: heterogeneous memory management (HMM for short) Jérôme Glisse
2017-01-12 16:30 ` [HMM v16 07/15] mm/hmm/mirror: mirror process address space on device with HMM helpers Jérôme Glisse
2017-01-12 16:30 ` [HMM v16 08/15] mm/hmm/mirror: helper to snapshot CPU page table Jérôme Glisse
2017-01-12 16:30 ` [HMM v16 09/15] mm/hmm/mirror: device page fault handler Jérôme Glisse
2017-01-12 16:30 ` [HMM v16 10/15] mm/hmm/migrate: support un-addressable ZONE_DEVICE page in migration Jérôme Glisse
2017-01-12 16:30 ` [HMM v16 11/15] mm/hmm/migrate: add new boolean copy flag to migratepage() callback Jérôme Glisse
2017-01-12 16:30 ` [HMM v16 12/15] mm/hmm/migrate: new memory migration helper for use with device memory v2 Jérôme Glisse
2017-01-12 16:30 ` [HMM v16 13/15] mm/hmm/migrate: optimize page map once in vma being migrated Jérôme Glisse
2017-01-12 16:30 ` [HMM v16 14/15] mm/hmm/devmem: device driver helper to hotplug ZONE_DEVICE memory v2 Jérôme Glisse
2017-01-12 16:30 ` [HMM v16 15/15] mm/hmm/devmem: dummy HMM device as an helper for ZONE_DEVICE memory Jérôme Glisse
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAPcyv4gnXyxHGitBCLbksy8PnHtePQ8260DKiF7CX8FXj2CtFQ@mail.gmail.com \
--to=dan.j.williams@intel.com \
--cc=akpm@linux-foundation.org \
--cc=jglisse@redhat.com \
--cc=jhubbard@nvidia.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=ross.zwisler@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox