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Message-ID: <1898385.DmbL8g47rR@nvdebian>
Date: Mon, 31 Jan 2022 17:20:54 +1100
From: Alistair Popple <apopple@...dia.com>
To: <akpm@...ux-foundation.org>, <Felix.Kuehling@....com>,
<linux-mm@...ck.org>, <rcampbell@...dia.com>,
<linux-ext4@...r.kernel.org>, <linux-xfs@...r.kernel.org>,
Alex Sierra <alex.sierra@....com>
CC: <amd-gfx@...ts.freedesktop.org>, <dri-devel@...ts.freedesktop.org>,
<hch@....de>, <jgg@...dia.com>, <jglisse@...hat.com>,
<willy@...radead.org>
Subject: Re: [PATCH v5 01/10] mm: add zone device coherent type memory support
Looks good, feel free to add:
Reviewed-by: Alistair Popple <apopple@...dia.com>
On Saturday, 29 January 2022 7:08:16 AM AEDT Alex Sierra wrote:
> Device memory that is cache coherent from device and CPU point of view.
> This is used on platforms that have an advanced system bus (like CAPI
> or CXL). Any page of a process can be migrated to such memory. However,
> no one should be allowed to pin such memory so that it can always be
> evicted.
>
> Signed-off-by: Alex Sierra <alex.sierra@....com>
> Acked-by: Felix Kuehling <Felix.Kuehling@....com>
> ---
> v4:
> - use the same system entry path for coherent device pages at
> migrate_vma_insert_page.
>
> - Add coherent device type support for try_to_migrate /
> try_to_migrate_one.
> ---
> include/linux/memremap.h | 8 +++++++
> include/linux/mm.h | 16 ++++++++++++++
> mm/memcontrol.c | 6 +++---
> mm/memory-failure.c | 8 +++++--
> mm/memremap.c | 14 ++++++++++++-
> mm/migrate.c | 45 ++++++++++++++++++++--------------------
> mm/rmap.c | 5 +++--
> 7 files changed, 71 insertions(+), 31 deletions(-)
>
> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
> index 1fafcc38acba..727b8c789193 100644
> --- a/include/linux/memremap.h
> +++ b/include/linux/memremap.h
> @@ -39,6 +39,13 @@ struct vmem_altmap {
> * A more complete discussion of unaddressable memory may be found in
> * include/linux/hmm.h and Documentation/vm/hmm.rst.
> *
> + * MEMORY_DEVICE_COHERENT:
> + * Device memory that is cache coherent from device and CPU point of view. This
> + * is used on platforms that have an advanced system bus (like CAPI or CXL). A
> + * driver can hotplug the device memory using ZONE_DEVICE and with that memory
> + * type. Any page of a process can be migrated to such memory. However no one
> + * should be allowed to pin such memory so that it can always be evicted.
> + *
> * MEMORY_DEVICE_FS_DAX:
> * Host memory that has similar access semantics as System RAM i.e. DMA
> * coherent and supports page pinning. In support of coordinating page
> @@ -59,6 +66,7 @@ struct vmem_altmap {
> enum memory_type {
> /* 0 is reserved to catch uninitialized type fields */
> MEMORY_DEVICE_PRIVATE = 1,
> + MEMORY_DEVICE_COHERENT,
> MEMORY_DEVICE_FS_DAX,
> MEMORY_DEVICE_GENERIC,
> MEMORY_DEVICE_PCI_P2PDMA,
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index e1a84b1e6787..0c61bf40edef 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1106,6 +1106,7 @@ static inline bool page_is_devmap_managed(struct page *page)
> return false;
> switch (page->pgmap->type) {
> case MEMORY_DEVICE_PRIVATE:
> + case MEMORY_DEVICE_COHERENT:
> case MEMORY_DEVICE_FS_DAX:
> return true;
> default:
> @@ -1135,6 +1136,21 @@ static inline bool is_device_private_page(const struct page *page)
> page->pgmap->type == MEMORY_DEVICE_PRIVATE;
> }
>
> +static inline bool is_device_coherent_page(const struct page *page)
> +{
> + return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) &&
> + is_zone_device_page(page) &&
> + page->pgmap->type == MEMORY_DEVICE_COHERENT;
> +}
> +
> +static inline bool is_dev_private_or_coherent_page(const struct page *page)
> +{
> + return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) &&
> + is_zone_device_page(page) &&
> + (page->pgmap->type == MEMORY_DEVICE_PRIVATE ||
> + page->pgmap->type == MEMORY_DEVICE_COHERENT);
> +}
> +
> static inline bool is_pci_p2pdma_page(const struct page *page)
> {
> return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) &&
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 09d342c7cbd0..0882b5b2a857 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5691,8 +5691,8 @@ static int mem_cgroup_move_account(struct page *page,
> * 2(MC_TARGET_SWAP): if the swap entry corresponding to this pte is a
> * target for charge migration. if @target is not NULL, the entry is stored
> * in target->ent.
> - * 3(MC_TARGET_DEVICE): like MC_TARGET_PAGE but page is MEMORY_DEVICE_PRIVATE
> - * (so ZONE_DEVICE page and thus not on the lru).
> + * 3(MC_TARGET_DEVICE): like MC_TARGET_PAGE but page is device memory and
> + * thus not on the lru.
> * For now we such page is charge like a regular page would be as for all
> * intent and purposes it is just special memory taking the place of a
> * regular page.
> @@ -5726,7 +5726,7 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
> */
> if (page_memcg(page) == mc.from) {
> ret = MC_TARGET_PAGE;
> - if (is_device_private_page(page))
> + if (is_dev_private_or_coherent_page(page))
> ret = MC_TARGET_DEVICE;
> if (target)
> target->page = page;
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 14ae5c18e776..e83740f7f05e 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1611,12 +1611,16 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
> goto unlock;
> }
>
> - if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
> + switch (pgmap->type) {
> + case MEMORY_DEVICE_PRIVATE:
> + case MEMORY_DEVICE_COHERENT:
> /*
> - * TODO: Handle HMM pages which may need coordination
> + * TODO: Handle device pages which may need coordination
> * with device-side memory.
> */
> goto unlock;
> + default:
> + break;
> }
>
> /*
> diff --git a/mm/memremap.c b/mm/memremap.c
> index 6aa5f0c2d11f..354c8027823f 100644
> --- a/mm/memremap.c
> +++ b/mm/memremap.c
> @@ -44,6 +44,7 @@ EXPORT_SYMBOL(devmap_managed_key);
> static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
> {
> if (pgmap->type == MEMORY_DEVICE_PRIVATE ||
> + pgmap->type == MEMORY_DEVICE_COHERENT ||
> pgmap->type == MEMORY_DEVICE_FS_DAX)
> static_branch_dec(&devmap_managed_key);
> }
> @@ -51,6 +52,7 @@ static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
> static void devmap_managed_enable_get(struct dev_pagemap *pgmap)
> {
> if (pgmap->type == MEMORY_DEVICE_PRIVATE ||
> + pgmap->type == MEMORY_DEVICE_COHERENT ||
> pgmap->type == MEMORY_DEVICE_FS_DAX)
> static_branch_inc(&devmap_managed_key);
> }
> @@ -327,6 +329,16 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
> return ERR_PTR(-EINVAL);
> }
> break;
> + case MEMORY_DEVICE_COHERENT:
> + if (!pgmap->ops->page_free) {
> + WARN(1, "Missing page_free method\n");
> + return ERR_PTR(-EINVAL);
> + }
> + if (!pgmap->owner) {
> + WARN(1, "Missing owner\n");
> + return ERR_PTR(-EINVAL);
> + }
> + break;
> case MEMORY_DEVICE_FS_DAX:
> if (!IS_ENABLED(CONFIG_ZONE_DEVICE) ||
> IS_ENABLED(CONFIG_FS_DAX_LIMITED)) {
> @@ -469,7 +481,7 @@ EXPORT_SYMBOL_GPL(get_dev_pagemap);
> void free_devmap_managed_page(struct page *page)
> {
> /* notify page idle for dax */
> - if (!is_device_private_page(page)) {
> + if (!is_dev_private_or_coherent_page(page)) {
> wake_up_var(&page->_refcount);
> return;
> }
> diff --git a/mm/migrate.c b/mm/migrate.c
> index c7da064b4781..cd137aedcfe5 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -345,7 +345,7 @@ static int expected_page_refs(struct address_space *mapping, struct page *page)
> * Device private pages have an extra refcount as they are
> * ZONE_DEVICE pages.
> */
> - expected_count += is_device_private_page(page);
> + expected_count += is_dev_private_or_coherent_page(page);
> if (mapping)
> expected_count += compound_nr(page) + page_has_private(page);
>
> @@ -2611,7 +2611,7 @@ EXPORT_SYMBOL(migrate_vma_setup);
> * handle_pte_fault()
> * do_anonymous_page()
> * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
> - * private page.
> + * private or coherent page.
> */
> static void migrate_vma_insert_page(struct migrate_vma *migrate,
> unsigned long addr,
> @@ -2676,25 +2676,24 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
> */
> __SetPageUptodate(page);
>
> - if (is_zone_device_page(page)) {
> - if (is_device_private_page(page)) {
> - swp_entry_t swp_entry;
> + if (is_device_private_page(page)) {
> + swp_entry_t swp_entry;
>
> - if (vma->vm_flags & VM_WRITE)
> - swp_entry = make_writable_device_private_entry(
> - page_to_pfn(page));
> - else
> - swp_entry = make_readable_device_private_entry(
> - page_to_pfn(page));
> - entry = swp_entry_to_pte(swp_entry);
> - } else {
> - /*
> - * For now we only support migrating to un-addressable
> - * device memory.
> - */
> - pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
> - goto abort;
> - }
> + if (vma->vm_flags & VM_WRITE)
> + swp_entry = make_writable_device_private_entry(
> + page_to_pfn(page));
> + else
> + swp_entry = make_readable_device_private_entry(
> + page_to_pfn(page));
> + entry = swp_entry_to_pte(swp_entry);
> + } else if (is_zone_device_page(page) &&
> + !is_device_coherent_page(page)) {
> + /*
> + * We support migrating to private and coherent types
> + * for device zone memory.
> + */
> + pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
> + goto abort;
> } else {
> entry = mk_pte(page, vma->vm_page_prot);
> if (vma->vm_flags & VM_WRITE)
> @@ -2796,10 +2795,10 @@ void migrate_vma_pages(struct migrate_vma *migrate)
> mapping = page_mapping(page);
>
> if (is_zone_device_page(newpage)) {
> - if (is_device_private_page(newpage)) {
> + if (is_dev_private_or_coherent_page(newpage)) {
> /*
> - * For now only support private anonymous when
> - * migrating to un-addressable device memory.
> + * For now only support private and coherent
> + * anonymous when migrating to device memory.
> */
> if (mapping) {
> migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 6a1e8c7f6213..f2bd5a3da72c 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1835,7 +1835,7 @@ static bool try_to_migrate_one(struct page *page, struct vm_area_struct *vma,
> /* Update high watermark before we lower rss */
> update_hiwater_rss(mm);
>
> - if (is_zone_device_page(page)) {
> + if (is_device_private_page(page)) {
> unsigned long pfn = page_to_pfn(page);
> swp_entry_t entry;
> pte_t swp_pte;
> @@ -1976,7 +1976,8 @@ void try_to_migrate(struct page *page, enum ttu_flags flags)
> TTU_SYNC)))
> return;
>
> - if (is_zone_device_page(page) && !is_device_private_page(page))
> + if (is_zone_device_page(page) &&
> + !is_dev_private_or_coherent_page(page))
> return;
>
> /*
>
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