From dcea65777f7d089e7d7ec0b135e1c1aca06faf1c Mon Sep 17 00:00:00 2001 From: David Vrabel Date: Fri, 11 Jul 2014 16:42:34 +0100 Subject: [PATCH] x86/xen: safely map and unmap grant frames when in atomic context arch_gnttab_map_frames() and arch_gnttab_unmap_frames() are called in atomic context but were calling alloc_vm_area() which might sleep. Also, if a driver attempts to allocate a grant ref from an interrupt and the table needs expanding, then the CPU may already by in lazy MMU mode and apply_to_page_range() will BUG when it tries to re-enable lazy MMU mode. These two functions are only used in PV guests. Introduce arch_gnttab_init() to allocates the virtual address space in advance. Avoid the use of apply_to_page_range() by using saving and using the array of PTE addresses from the alloc_vm_area() call (which ensures that the required page tables are pre-allocated). Signed-off-by: David Vrabel Signed-off-by: Konrad Rzeszutek Wilk [Backported to 3.13.10.] Signed-off-by: David Vrabel --- arch/arm/xen/grant-table.c | 5 ++ arch/x86/xen/grant-table.c | 148 +++++++++++++++++++++++++++----------------- drivers/xen/grant-table.c | 5 ++ include/xen/grant_table.h | 1 + 4 files changed, 102 insertions(+), 57 deletions(-) diff --git a/arch/arm/xen/grant-table.c b/arch/arm/xen/grant-table.c index 859a9bb..91cf08b 100644 --- a/arch/arm/xen/grant-table.c +++ b/arch/arm/xen/grant-table.c @@ -51,3 +51,8 @@ int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes, { return -ENOSYS; } + +int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status) +{ + return 0; +} diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c index 3a5f55d..4d2c9bf 100644 --- a/arch/x86/xen/grant-table.c +++ b/arch/x86/xen/grant-table.c @@ -36,92 +36,126 @@ #include #include +#include #include #include #include #include +#include #include -static int map_pte_fn(pte_t *pte, struct page *pmd_page, - unsigned long addr, void *data) -{ - unsigned long **frames = (unsigned long **)data; - - set_pte_at(&init_mm, addr, pte, mfn_pte((*frames)[0], PAGE_KERNEL)); - (*frames)++; - return 0; -} - -/* - * This function is used to map shared frames to store grant status. It is - * different from map_pte_fn above, the frames type here is uint64_t. - */ -static int map_pte_fn_status(pte_t *pte, struct page *pmd_page, - unsigned long addr, void *data) -{ - uint64_t **frames = (uint64_t **)data; - - set_pte_at(&init_mm, addr, pte, mfn_pte((*frames)[0], PAGE_KERNEL)); - (*frames)++; - return 0; -} - -static int unmap_pte_fn(pte_t *pte, struct page *pmd_page, - unsigned long addr, void *data) -{ - - set_pte_at(&init_mm, addr, pte, __pte(0)); - return 0; -} +static struct gnttab_vm_area { + struct vm_struct *area; + pte_t **ptes; +} gnttab_shared_vm_area, gnttab_status_vm_area; int arch_gnttab_map_shared(unsigned long *frames, unsigned long nr_gframes, unsigned long max_nr_gframes, void **__shared) { - int rc; void *shared = *__shared; + unsigned long addr; + unsigned long i; + + if (shared == NULL) + *__shared = shared = gnttab_shared_vm_area.area->addr; - if (shared == NULL) { - struct vm_struct *area = - alloc_vm_area(PAGE_SIZE * max_nr_gframes, NULL); - BUG_ON(area == NULL); - shared = area->addr; - *__shared = shared; + addr = (unsigned long)shared; + + for (i = 0; i < nr_gframes; i++) { + set_pte_at(&init_mm, addr, gnttab_shared_vm_area.ptes[i], + mfn_pte(frames[i], PAGE_KERNEL)); + addr += PAGE_SIZE; } - rc = apply_to_page_range(&init_mm, (unsigned long)shared, - PAGE_SIZE * nr_gframes, - map_pte_fn, &frames); - return rc; + return 0; } int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes, unsigned long max_nr_gframes, grant_status_t **__shared) { - int rc; grant_status_t *shared = *__shared; + unsigned long addr; + unsigned long i; + + if (shared == NULL) + *__shared = shared = gnttab_status_vm_area.area->addr; - if (shared == NULL) { - /* No need to pass in PTE as we are going to do it - * in apply_to_page_range anyhow. */ - struct vm_struct *area = - alloc_vm_area(PAGE_SIZE * max_nr_gframes, NULL); - BUG_ON(area == NULL); - shared = area->addr; - *__shared = shared; + addr = (unsigned long)shared; + + for (i = 0; i < nr_gframes; i++) { + set_pte_at(&init_mm, addr, gnttab_status_vm_area.ptes[i], + mfn_pte(frames[i], PAGE_KERNEL)); + addr += PAGE_SIZE; } - rc = apply_to_page_range(&init_mm, (unsigned long)shared, - PAGE_SIZE * nr_gframes, - map_pte_fn_status, &frames); - return rc; + return 0; } void arch_gnttab_unmap(void *shared, unsigned long nr_gframes) { - apply_to_page_range(&init_mm, (unsigned long)shared, - PAGE_SIZE * nr_gframes, unmap_pte_fn, NULL); + pte_t **ptes; + unsigned long addr; + unsigned long i; + + if (shared == gnttab_status_vm_area.area->addr) + ptes = gnttab_status_vm_area.ptes; + else + ptes = gnttab_shared_vm_area.ptes; + + addr = (unsigned long)shared; + + for (i = 0; i < nr_gframes; i++) { + set_pte_at(&init_mm, addr, ptes[i], __pte(0)); + addr += PAGE_SIZE; + } +} + +static int arch_gnttab_valloc(struct gnttab_vm_area *area, unsigned nr_frames) +{ + area->ptes = kmalloc(sizeof(pte_t *) * nr_frames, GFP_KERNEL); + if (area->ptes == NULL) + return -ENOMEM; + + area->area = alloc_vm_area(PAGE_SIZE * nr_frames, area->ptes); + if (area->area == NULL) { + kfree(area->ptes); + return -ENOMEM; + } + + return 0; +} + +static void arch_gnttab_vfree(struct gnttab_vm_area *area) +{ + free_vm_area(area->area); + kfree(area->ptes); +} + +int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status) +{ + int ret; + + if (!xen_pv_domain()) + return 0; + + ret = arch_gnttab_valloc(&gnttab_shared_vm_area, nr_shared); + if (ret < 0) + return ret; + + /* + * Always allocate the space for the status frames in case + * we're migrated to a host with V2 support. + */ + ret = arch_gnttab_valloc(&gnttab_status_vm_area, nr_status); + if (ret < 0) + goto err; + + return 0; + err: + arch_gnttab_vfree(&gnttab_shared_vm_area); + return -ENOMEM; } diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c index aa846a4..b983a99 100644 --- a/drivers/xen/grant-table.c +++ b/drivers/xen/grant-table.c @@ -1250,6 +1250,11 @@ int gnttab_init(void) } } + ret = arch_gnttab_init(boot_max_nr_grant_frames, + nr_status_frames(boot_max_nr_grant_frames)); + if (ret < 0) + goto ini_nomem; + if (gnttab_setup() < 0) { ret = -ENODEV; goto ini_nomem; diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h index 694dcaf..bbb6c50 100644 --- a/include/xen/grant_table.h +++ b/include/xen/grant_table.h @@ -170,6 +170,7 @@ gnttab_set_unmap_op(struct gnttab_unmap_grant_ref *unmap, phys_addr_t addr, unmap->dev_bus_addr = 0; } +int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status); int arch_gnttab_map_shared(xen_pfn_t *frames, unsigned long nr_gframes, unsigned long max_nr_gframes, void **__shared); -- 1.7.10.4