To be used in order to create foreign mappings. This is based on the ZONE_DEVICE facility which is used by persistent memory devices in order to create struct pages and kernel virtual mappings for the IOMEM areas of such devices. Note that on kernels without support for ZONE_DEVICE Xen will fallback to use ballooned pages in order to create foreign mappings.

The newly added helpers use the same parameters as the existing {alloc/free}_xenballooned_pages functions, which allows for in-place replacement of the callers. Once a memory region has been added to be used as scratch mapping space it will no longer be released, and pages returned are kept in a linked list. This allows to have a buffer of pages and prevents resorting to frequent additions and removals of regions.

If enabled (because ZONE_DEVICE is supported) the usage of the new functionality untangles Xen balloon and RAM hotplug from the usage of unpopulated physical memory ranges to map foreign pages, which is the correct thing to do in order to avoid mappings of foreign pages depend on memory hotplug.

Signed-off-by: Roger Pau Monné roger.pau@citrix.com --- I've not added a new memory_type type and just used MEMORY_DEVICE_DEVDAX which seems to be what we want for such memory regions. I'm unsure whether abusing this type is fine, or if I should instead add a specific type, maybe MEMORY_DEVICE_GENERIC? I don't think we should be using a specific Xen type at all. --- Cc: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com Cc: David Airlie airlied@linux.ie Cc: Daniel Vetter daniel@ffwll.ch Cc: Boris Ostrovsky boris.ostrovsky@oracle.com Cc: Juergen Gross jgross@suse.com Cc: Stefano Stabellini sstabellini@kernel.org Cc: Dan Carpenter dan.carpenter@oracle.com Cc: Roger Pau Monne roger.pau@citrix.com Cc: Wei Liu wl@xen.org Cc: Yan Yankovskyi yyankovskyi@gmail.com Cc: dri-devel@lists.freedesktop.org Cc: xen-devel@lists.xenproject.org Cc: linux-mm@kvack.org Cc: David Hildenbrand david@redhat.com Cc: Michal Hocko mhocko@kernel.org Cc: Dan Williams dan.j.williams@intel.com --- Changes since v2: - Drop BUILD_BUG_ON regarding PVMMU page sizes. - Use a SPDX license identifier. - Call fill with only the minimum required number of pages. - Include xen.h header in xen_drm_front_gem.c. - Use less generic function names. - Exit early from the init function if not a PV guest. - Don't use all caps for region name. --- drivers/gpu/drm/xen/xen_drm_front_gem.c | 9 +- drivers/xen/Makefile | 1 + drivers/xen/balloon.c | 4 +- drivers/xen/grant-table.c | 4 +- drivers/xen/privcmd.c | 4 +- drivers/xen/unpopulated-alloc.c | 185 ++++++++++++++++++++++++ drivers/xen/xenbus/xenbus_client.c | 6 +- drivers/xen/xlate_mmu.c | 4 +- include/xen/xen.h | 9 ++ 9 files changed, 211 insertions(+), 15 deletions(-) create mode 100644 drivers/xen/unpopulated-alloc.c

diff --git a/drivers/gpu/drm/xen/xen_drm_front_gem.c b/drivers/gpu/drm/xen/xen_drm_front_gem.c index f0b85e094111..270e1bd3e4da 100644 --- a/drivers/gpu/drm/xen/xen_drm_front_gem.c +++ b/drivers/gpu/drm/xen/xen_drm_front_gem.c @@ -18,6 +18,7 @@ #include <drm/drm_probe_helper.h>

#include <xen/balloon.h> +#include <xen/xen.h>

#include "xen_drm_front.h" #include "xen_drm_front_gem.h" @@ -99,8 +100,8 @@ static struct xen_gem_object *gem_create(struct drm_device *dev, size_t size) * allocate ballooned pages which will be used to map * grant references provided by the backend */ - ret = alloc_xenballooned_pages(xen_obj->num_pages, - xen_obj->pages); + ret = xen_alloc_unpopulated_pages(xen_obj->num_pages, + xen_obj->pages); if (ret < 0) { DRM_ERROR("Cannot allocate %zu ballooned pages: %d\n", xen_obj->num_pages, ret); @@ -152,8 +153,8 @@ void xen_drm_front_gem_free_object_unlocked(struct drm_gem_object *gem_obj) } else { if (xen_obj->pages) { if (xen_obj->be_alloc) { - free_xenballooned_pages(xen_obj->num_pages, - xen_obj->pages); + xen_free_unpopulated_pages(xen_obj->num_pages, + xen_obj->pages); gem_free_pages_array(xen_obj); } else { drm_gem_put_pages(&xen_obj->base, diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile index 0d322f3d90cd..788a5d9c8ef0 100644 --- a/drivers/xen/Makefile +++ b/drivers/xen/Makefile @@ -42,3 +42,4 @@ xen-gntdev-$(CONFIG_XEN_GNTDEV_DMABUF) += gntdev-dmabuf.o xen-gntalloc-y := gntalloc.o xen-privcmd-y := privcmd.o privcmd-buf.o obj-$(CONFIG_XEN_FRONT_PGDIR_SHBUF) += xen-front-pgdir-shbuf.o +obj-$(CONFIG_ZONE_DEVICE) += unpopulated-alloc.o diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index b1d8b028bf80..815ef10eb2ff 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -654,7 +654,7 @@ void free_xenballooned_pages(int nr_pages, struct page **pages) } EXPORT_SYMBOL(free_xenballooned_pages);

-#ifdef CONFIG_XEN_PV +#if defined(CONFIG_XEN_PV) && !defined(CONFIG_ZONE_DEVICE) static void __init balloon_add_region(unsigned long start_pfn, unsigned long pages) { @@ -708,7 +708,7 @@ static int __init balloon_init(void) register_sysctl_table(xen_root); #endif

-#ifdef CONFIG_XEN_PV +#if defined(CONFIG_XEN_PV) && !defined(CONFIG_ZONE_DEVICE) { int i;

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c index 8d06bf1cc347..523dcdf39cc9 100644 --- a/drivers/xen/grant-table.c +++ b/drivers/xen/grant-table.c @@ -801,7 +801,7 @@ int gnttab_alloc_pages(int nr_pages, struct page **pages) { int ret;

- ret = alloc_xenballooned_pages(nr_pages, pages); + ret = xen_alloc_unpopulated_pages(nr_pages, pages); if (ret < 0) return ret;

@@ -836,7 +836,7 @@ EXPORT_SYMBOL_GPL(gnttab_pages_clear_private); void gnttab_free_pages(int nr_pages, struct page **pages) { gnttab_pages_clear_private(nr_pages, pages); - free_xenballooned_pages(nr_pages, pages); + xen_free_unpopulated_pages(nr_pages, pages); } EXPORT_SYMBOL_GPL(gnttab_free_pages);

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c index a250d118144a..56000ab70974 100644 --- a/drivers/xen/privcmd.c +++ b/drivers/xen/privcmd.c @@ -425,7 +425,7 @@ static int alloc_empty_pages(struct vm_area_struct *vma, int numpgs) if (pages == NULL) return -ENOMEM;

- rc = alloc_xenballooned_pages(numpgs, pages); + rc = xen_alloc_unpopulated_pages(numpgs, pages); if (rc != 0) { pr_warn("%s Could not alloc %d pfns rc:%d\n", __func__, numpgs, rc); @@ -900,7 +900,7 @@ static void privcmd_close(struct vm_area_struct *vma)

rc = xen_unmap_domain_gfn_range(vma, numgfns, pages); if (rc == 0) - free_xenballooned_pages(numpgs, pages); + xen_free_unpopulated_pages(numpgs, pages); else pr_crit("unable to unmap MFN range: leaking %d pages. rc=%d\n", numpgs, rc); diff --git a/drivers/xen/unpopulated-alloc.c b/drivers/xen/unpopulated-alloc.c new file mode 100644 index 000000000000..c50450375922 --- /dev/null +++ b/drivers/xen/unpopulated-alloc.c @@ -0,0 +1,185 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <linux/errno.h> +#include <linux/gfp.h> +#include <linux/kernel.h> +#include <linux/mm.h> +#include <linux/memremap.h> +#include <linux/slab.h> + +#include <asm/page.h> + +#include <xen/page.h> +#include <xen/xen.h> + +static DEFINE_MUTEX(list_lock); +static LIST_HEAD(page_list); +static unsigned int list_count; + +static int fill_list(unsigned int nr_pages) +{ + struct dev_pagemap *pgmap; + void *vaddr; + unsigned int i, alloc_pages = round_up(nr_pages, PAGES_PER_SECTION); + int nid, ret; + + pgmap = kzalloc(sizeof(*pgmap), GFP_KERNEL); + if (!pgmap) + return -ENOMEM; + + pgmap->type = MEMORY_DEVICE_DEVDAX; + pgmap->res.name = "Xen scratch"; + pgmap->res.flags = IORESOURCE_MEM | IORESOURCE_BUSY; + + ret = allocate_resource(&iomem_resource, &pgmap->res, + alloc_pages * PAGE_SIZE, 0, -1, + PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL); + if (ret < 0) { + pr_err("Cannot allocate new IOMEM resource\n"); + kfree(pgmap); + return ret; + } + + nid = memory_add_physaddr_to_nid(pgmap->res.start); + +#ifdef CONFIG_XEN_HAVE_PVMMU + /* + * memremap will build page tables for the new memory so + * the p2m must contain invalid entries so the correct + * non-present PTEs will be written. + * + * If a failure occurs, the original (identity) p2m entries + * are not restored since this region is now known not to + * conflict with any devices. + */ + if (!xen_feature(XENFEAT_auto_translated_physmap)) { + xen_pfn_t pfn = PFN_DOWN(pgmap->res.start); + + for (i = 0; i < alloc_pages; i++) { + if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) { + pr_warn("set_phys_to_machine() failed, no memory added\n"); + release_resource(&pgmap->res); + kfree(pgmap); + return -ENOMEM; + } + } + } +#endif + + vaddr = memremap_pages(pgmap, nid); + if (IS_ERR(vaddr)) { + pr_err("Cannot remap memory range\n"); + release_resource(&pgmap->res); + kfree(pgmap); + return PTR_ERR(vaddr); + } + + for (i = 0; i < alloc_pages; i++) { + struct page *pg = virt_to_page(vaddr + PAGE_SIZE * i); + + BUG_ON(!virt_addr_valid(vaddr + PAGE_SIZE * i)); + list_add(&pg->lru, &page_list); + list_count++; + } + + return 0; +} + +/** + * xen_alloc_unpopulated_pages - alloc unpopulated pages + * @nr_pages: Number of pages + * @pages: pages returned + * @return 0 on success, error otherwise + */ +int xen_alloc_unpopulated_pages(unsigned int nr_pages, struct page **pages) +{ + unsigned int i; + int ret = 0; + + mutex_lock(&list_lock); + if (list_count < nr_pages) { + ret = fill_list(nr_pages - list_count); + if (ret) + goto out; + } + + for (i = 0; i < nr_pages; i++) { + struct page *pg = list_first_entry_or_null(&page_list, + struct page, + lru); + + BUG_ON(!pg); + list_del(&pg->lru); + list_count--; + pages[i] = pg; + +#ifdef CONFIG_XEN_HAVE_PVMMU + if (!xen_feature(XENFEAT_auto_translated_physmap)) { + ret = xen_alloc_p2m_entry(page_to_pfn(pg)); + if (ret < 0) { + unsigned int j; + + for (j = 0; j <= i; j++) { + list_add(&pages[j]->lru, &page_list); + list_count++; + } + goto out; + } + } +#endif + } + +out: + mutex_unlock(&list_lock); + return ret; +} +EXPORT_SYMBOL(xen_alloc_unpopulated_pages); + +/** + * xen_free_unpopulated_pages - return unpopulated pages + * @nr_pages: Number of pages + * @pages: pages to return + */ +void xen_free_unpopulated_pages(unsigned int nr_pages, struct page **pages) +{ + unsigned int i; + + mutex_lock(&list_lock); + for (i = 0; i < nr_pages; i++) { + list_add(&pages[i]->lru, &page_list); + list_count++; + } + mutex_unlock(&list_lock); +} +EXPORT_SYMBOL(xen_free_unpopulated_pages); + +#ifdef CONFIG_XEN_PV +static int __init init(void) +{ + unsigned int i; + + if (!xen_domain()) + return -ENODEV; + + if (!xen_pv_domain()) + return 0; + + /* + * Initialize with pages from the extra memory regions (see + * arch/x86/xen/setup.c). + */ + for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) { + unsigned int j; + + for (j = 0; j < xen_extra_mem[i].n_pfns; j++) { + struct page *pg = + pfn_to_page(xen_extra_mem[i].start_pfn + j); + + list_add(&pg->lru, &page_list); + list_count++; + } + } + + return 0; +} +subsys_initcall(init); +#endif diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c index 786fbb7d8be0..70b6c4780fbd 100644 --- a/drivers/xen/xenbus/xenbus_client.c +++ b/drivers/xen/xenbus/xenbus_client.c @@ -615,7 +615,7 @@ static int xenbus_map_ring_hvm(struct xenbus_device *dev, bool leaked = false; unsigned int nr_pages = XENBUS_PAGES(nr_grefs);

- err = alloc_xenballooned_pages(nr_pages, node->hvm.pages); + err = xen_alloc_unpopulated_pages(nr_pages, node->hvm.pages); if (err) goto out_err;

@@ -656,7 +656,7 @@ static int xenbus_map_ring_hvm(struct xenbus_device *dev, addr, nr_pages); out_free_ballooned_pages: if (!leaked) - free_xenballooned_pages(nr_pages, node->hvm.pages); + xen_free_unpopulated_pages(nr_pages, node->hvm.pages); out_err: return err; } @@ -852,7 +852,7 @@ static int xenbus_unmap_ring_hvm(struct xenbus_device *dev, void *vaddr) info.addrs); if (!rv) { vunmap(vaddr); - free_xenballooned_pages(nr_pages, node->hvm.pages); + xen_free_unpopulated_pages(nr_pages, node->hvm.pages); } else WARN(1, "Leaking %p, size %u page(s)\n", vaddr, nr_pages); diff --git a/drivers/xen/xlate_mmu.c b/drivers/xen/xlate_mmu.c index 7b1077f0abcb..34742c6e189e 100644 --- a/drivers/xen/xlate_mmu.c +++ b/drivers/xen/xlate_mmu.c @@ -232,7 +232,7 @@ int __init xen_xlate_map_ballooned_pages(xen_pfn_t **gfns, void **virt, kfree(pages); return -ENOMEM; } - rc = alloc_xenballooned_pages(nr_pages, pages); + rc = xen_alloc_unpopulated_pages(nr_pages, pages); if (rc) { pr_warn("%s Couldn't balloon alloc %ld pages rc:%d\n", __func__, nr_pages, rc); @@ -249,7 +249,7 @@ int __init xen_xlate_map_ballooned_pages(xen_pfn_t **gfns, void **virt, if (!vaddr) { pr_warn("%s Couldn't map %ld pages rc:%d\n", __func__, nr_pages, rc); - free_xenballooned_pages(nr_pages, pages); + xen_free_unpopulated_pages(nr_pages, pages); kfree(pages); kfree(pfns); return -ENOMEM; diff --git a/include/xen/xen.h b/include/xen/xen.h index 19a72f591e2b..e93b47e5e378 100644 --- a/include/xen/xen.h +++ b/include/xen/xen.h @@ -52,4 +52,13 @@ bool xen_biovec_phys_mergeable(const struct bio_vec *vec1, extern u64 xen_saved_max_mem_size; #endif

+#ifdef CONFIG_ZONE_DEVICE +int xen_alloc_unpopulated_pages(unsigned int nr_pages, struct page **pages); +void xen_free_unpopulated_pages(unsigned int nr_pages, struct page **pages); +#else +#define xen_alloc_unpopulated_pages alloc_xenballooned_pages +#define xen_free_unpopulated_pages free_xenballooned_pages +#include <xen/balloon.h> +#endif + #endif /* _XEN_XEN_H */