Hello, In XenServer we have seen the watchdog occasionally triggering during domain creation if 1GB pages are scrubbed in-place during physmap population. The following series attempt to mitigate this by adding preemption to page scrubbing in populate_physmap(). Also a new limit and command line option to signal the maximum allocation order when doing in-place scrubbing. This is set by default to CONFIG_DOMU_MAX_ORDER. Thanks, Roger. Roger Pau Monne (3): xen/mm: enforce SCRUB_DEBUG checks for MEMF_no_scrub allocations xen/mm: allow deferred scrub of physmap populate allocated pages xen/mm: limit non-scrubbed allocations to a specific order docs/misc/xen-command-line.pandoc | 9 +++ xen/common/domain.c | 17 +++++ xen/common/memory.c | 105 +++++++++++++++++++++++++++++- xen/common/page_alloc.c | 30 +++++++-- xen/include/xen/mm.h | 1 + xen/include/xen/sched.h | 5 ++ 6 files changed, 161 insertions(+), 6 deletions(-) -- 2.51.0 The logic in alloc_heap_pages() only checks for scrubbing pattern correctness when the caller doesn't pass MEMF_no_scrub in memflags. However already scrubbed pages can be checked for correctness, regardless of the caller having requested MEMF_no_scrub. Relax the checking around the check_one_page() call, to allow for calls with MEMF_no_scrub to also check the correctness of pages marked as already scrubbed when allocated. This widens the checking of scrubbing correctness, so it would also check the scrubbing correctness of MEMF_no_scrub allocations. Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> --- After discussing with Jan I've deliberately omitted the tag: Fixes: 0c5f2f9cefac ("mm: Make sure pages are scrubbed") The intended approach might have been to ensure the caller of alloc_heap_pages() gets properly scrubbed pages, rather than asserting the internal state of free pages is as expected. --- xen/common/page_alloc.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c index XXXXXXX..XXXXXXX 100644 --- a/xen/common/page_alloc.c +++ b/xen/common/page_alloc.c @@ -XXX,XX +XXX,XX @@ static struct page_info *alloc_heap_pages( spin_unlock(&heap_lock); - if ( first_dirty != INVALID_DIRTY_IDX || - (scrub_debug && !(memflags & MEMF_no_scrub)) ) + if ( first_dirty != INVALID_DIRTY_IDX || scrub_debug ) { bool cold = d && d != current->domain; @@ -XXX,XX +XXX,XX @@ static struct page_info *alloc_heap_pages( dirty_cnt++; } - else if ( !(memflags & MEMF_no_scrub) ) + else check_one_page(&pg[i]); } -- 2.51.0 Physmap population has the need to use pages as big as possible to reduce p2m shattering. However that triggers issues when big enough pages are not yet scrubbed, and so scrubbing must be done at allocation time. On some scenarios with added contention the watchdog can trigger: Watchdog timer detects that CPU55 is stuck! ----[ Xen-4.17.5-21 x86_64 debug=n Not tainted ]---- CPU: 55 RIP: e008:[<ffff82d040204c4a>] clear_page_sse2+0x1a/0x30 RFLAGS: 0000000000000202 CONTEXT: hypervisor (d0v12) [...] Xen call trace: [<ffff82d040204c4a>] R clear_page_sse2+0x1a/0x30 [<ffff82d04022a121>] S clear_domain_page+0x11/0x20 [<ffff82d04022c170>] S common/page_alloc.c#alloc_heap_pages+0x400/0x5a0 [<ffff82d04022d4a7>] S alloc_domheap_pages+0x67/0x180 [<ffff82d040226f9f>] S common/memory.c#populate_physmap+0x22f/0x3b0 [<ffff82d040228ec8>] S do_memory_op+0x728/0x1970 Introduce a mechanism to preempt page scrubbing in populate_physmap(). It relies on stashing the dirty page in the domain struct temporarily to preempt to guest context, so the scrubbing can resume when the domain re-enters the hypercall. The added deferral mechanism will only be used for domain construction, and is designed to be used with a single threaded domain builder. If the toolstack makes concurrent calls to XENMEM_populate_physmap for the same target domain it will trash stashed pages, resulting in slow domain physmap population. Note a similar issue is present in increase reservation. However that hypercall is likely to only be used once the domain is already running and the known implementations use 4K pages. It will be deal with in a separate patch using a different approach, that will also take care of the allocation in populate_physmap() once the domain is running. Fixes: 74d2e11ccfd2 ("mm: Scrub pages in alloc_heap_pages() if needed") Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> --- Changes since v1: - New in this version, different approach than v1. --- xen/common/domain.c | 17 +++++++ xen/common/memory.c | 105 +++++++++++++++++++++++++++++++++++++++- xen/common/page_alloc.c | 2 +- xen/include/xen/mm.h | 1 + xen/include/xen/sched.h | 5 ++ 5 files changed, 128 insertions(+), 2 deletions(-) diff --git a/xen/common/domain.c b/xen/common/domain.c index XXXXXXX..XXXXXXX 100644 --- a/xen/common/domain.c +++ b/xen/common/domain.c @@ -XXX,XX +XXX,XX @@ static void _domain_destroy(struct domain *d) XVFREE(d->console); + if ( d->pending_scrub ) + { + BUG_ON(d->creation_finished); + free_domheap_pages(d->pending_scrub, d->pending_scrub_order); + d->pending_scrub = NULL; + d->pending_scrub_order = 0; + d->pending_scrub_index = 0; + } + argo_destroy(d); rangeset_domain_destroy(d); @@ -XXX,XX +XXX,XX @@ int domain_unpause_by_systemcontroller(struct domain *d) */ if ( new == 0 && !d->creation_finished ) { + if ( d->pending_scrub ) + { + printk(XENLOG_ERR + "%pd: cannot be started with pending dirty pages, destroying\n", + d); + domain_crash(d); + return -EBUSY; + } d->creation_finished = true; arch_domain_creation_finished(d); } diff --git a/xen/common/memory.c b/xen/common/memory.c index XXXXXXX..XXXXXXX 100644 --- a/xen/common/memory.c +++ b/xen/common/memory.c @@ -XXX,XX +XXX,XX @@ static void increase_reservation(struct memop_args *a) a->nr_done = i; } +/* + * Temporary storage for a domain assigned page that's not been fully scrubbed. + * Stored pages must be domheap ones. + * + * The stashed page can be freed at any time by Xen, the caller must pass the + * order and NUMA node requirement to the fetch function to ensure the + * currently stashed page matches it's requirements. + */ +static void stash_allocation(struct domain *d, struct page_info *page, + unsigned int order, unsigned int scrub_index) +{ + BUG_ON(d->creation_finished); + + rspin_lock(&d->page_alloc_lock); + + /* + * Drop any stashed allocation to accommodated the current one. This + * interface is designed to be used for single-threaded domain creation. + */ + if ( d->pending_scrub ) + free_domheap_pages(d->pending_scrub, d->pending_scrub_order); + + d->pending_scrub_index = scrub_index; + d->pending_scrub_order = order; + d->pending_scrub = page; + + rspin_unlock(&d->page_alloc_lock); +} + +static struct page_info *get_stashed_allocation(struct domain *d, + unsigned int order, + nodeid_t node, + unsigned int *scrub_index) +{ + struct page_info *page = NULL; + + BUG_ON(d->creation_finished && d->pending_scrub); + + rspin_lock(&d->page_alloc_lock); + + /* + * If there's a pending page to scrub check it satisfies the current + * request. If it doesn't keep it stashed and return NULL. + */ + if ( !d->pending_scrub || d->pending_scrub_order != order || + (node != NUMA_NO_NODE && node != page_to_nid(d->pending_scrub)) ) + goto done; + else + { + page = d->pending_scrub; + *scrub_index = d->pending_scrub_index; + } + + /* + * The caller now owns the page, clear stashed information. Prevent + * concurrent usages of get_stashed_allocation() from returning the same + * page to different contexts. + */ + d->pending_scrub_index = 0; + d->pending_scrub_order = 0; + d->pending_scrub = NULL; + + done: + rspin_unlock(&d->page_alloc_lock); + + return page; +} + static void populate_physmap(struct memop_args *a) { struct page_info *page; @@ -XXX,XX +XXX,XX @@ static void populate_physmap(struct memop_args *a) } else { - page = alloc_domheap_pages(d, a->extent_order, a->memflags); + unsigned int scrub_start = 0; + nodeid_t node = + (a->memflags & MEMF_exact_node) ? MEMF_get_node(a->memflags) + : NUMA_NO_NODE; + + page = get_stashed_allocation(d, a->extent_order, node, + &scrub_start); + + if ( !page ) + page = alloc_domheap_pages(d, a->extent_order, + a->memflags | (d->creation_finished ? 0 + : MEMF_no_scrub)); if ( unlikely(!page) ) { @@ -XXX,XX +XXX,XX @@ static void populate_physmap(struct memop_args *a) goto out; } + if ( !d->creation_finished ) + { + unsigned int dirty_cnt = 0, j; + + /* Check if there's anything to scrub. */ + for ( j = scrub_start; j < (1U << a->extent_order); j++ ) + { + if ( !test_and_clear_bit(_PGC_need_scrub, + &page[j].count_info) ) + continue; + + scrub_one_page(&page[j], true); + + if ( (j + 1) != (1U << a->extent_order) && + !(++dirty_cnt & 0xff) && + hypercall_preempt_check() ) + { + a->preempted = 1; + stash_allocation(d, page, a->extent_order, ++j); + goto out; + } + } + } + if ( unlikely(a->memflags & MEMF_no_tlbflush) ) { for ( j = 0; j < (1U << a->extent_order); j++ ) diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c index XXXXXXX..XXXXXXX 100644 --- a/xen/common/page_alloc.c +++ b/xen/common/page_alloc.c @@ -XXX,XX +XXX,XX @@ static void page_list_add_scrub(struct page_info *pg, unsigned int node, # define scrub_page_cold clear_page_cold #endif -static void scrub_one_page(const struct page_info *pg, bool cold) +void scrub_one_page(const struct page_info *pg, bool cold) { void *ptr; diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h index XXXXXXX..XXXXXXX 100644 --- a/xen/include/xen/mm.h +++ b/xen/include/xen/mm.h @@ -XXX,XX +XXX,XX @@ unsigned long avail_domheap_pages_region( unsigned long avail_node_heap_pages(unsigned int nodeid); #define alloc_domheap_page(d,f) (alloc_domheap_pages(d,0,f)) #define free_domheap_page(p) (free_domheap_pages(p,0)) +void scrub_one_page(const struct page_info *pg, bool cold); int online_page(mfn_t mfn, uint32_t *status); int offline_page(mfn_t mfn, int broken, uint32_t *status); diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h index XXXXXXX..XXXXXXX 100644 --- a/xen/include/xen/sched.h +++ b/xen/include/xen/sched.h @@ -XXX,XX +XXX,XX @@ struct domain /* Pointer to console settings; NULL for system domains. */ struct domain_console *console; + + /* Pointer to allocated domheap page that possibly needs scrubbing. */ + struct page_info *pending_scrub; + unsigned int pending_scrub_order; + unsigned int pending_scrub_index; } __aligned(PAGE_SIZE); static inline struct page_list_head *page_to_list( -- 2.51.0 The current logic allows for up to 1G pages to be scrubbed in place, which can cause the watchdog to trigger in practice. Reduce the limit for in-place scrubbed allocations to a newly introduced define: CONFIG_DIRTY_MAX_ORDER. This currently defaults to CONFIG_DOMU_MAX_ORDER on all architectures. Also introduce a command line option to set the value. Fixes: 74d2e11ccfd2 ("mm: Scrub pages in alloc_heap_pages() if needed") Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> --- Changes since v1: - Split from previous patch. - Introduce a command line option to set the limit. --- docs/misc/xen-command-line.pandoc | 9 +++++++++ xen/common/page_alloc.c | 23 ++++++++++++++++++++++- 2 files changed, 31 insertions(+), 1 deletion(-) diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc index XXXXXXX..XXXXXXX 100644 --- a/docs/misc/xen-command-line.pandoc +++ b/docs/misc/xen-command-line.pandoc @@ -XXX,XX +XXX,XX @@ Specify the deepest C-state CPUs are permitted to be placed in, and optionally the maximum sub C-state to be used used. The latter only applies to the highest permitted C-state. +### max-order-dirty +> `= <integer>` + +Specify the maximum allocation order allowed when scrubbing allocated pages +in-place. The allocation is non-preemptive, and hence the value must be keep +low enough to avoid hogging the CPU for too long. + +Defaults to `CONFIG_DIRTY_MAX_ORDER` or if unset to `CONFIG_DOMU_MAX_ORDER`. + ### max_gsi_irqs (x86) > `= <integer>` diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c index XXXXXXX..XXXXXXX 100644 --- a/xen/common/page_alloc.c +++ b/xen/common/page_alloc.c @@ -XXX,XX +XXX,XX @@ static PAGE_LIST_HEAD(page_offlined_list); /* Broken page list, protected by heap_lock. */ static PAGE_LIST_HEAD(page_broken_list); +/* Maximum order allowed for allocations with MEMF_no_scrub. */ +#ifndef CONFIG_DIRTY_MAX_ORDER +# define CONFIG_DIRTY_MAX_ORDER CONFIG_DOMU_MAX_ORDER +#endif +static unsigned int __ro_after_init dirty_max_order = CONFIG_DIRTY_MAX_ORDER; +integer_param("max-order-dirty", dirty_max_order); + /************************* * BOOT-TIME ALLOCATOR */ @@ -XXX,XX +XXX,XX @@ static struct page_info *alloc_heap_pages( pg = get_free_buddy(zone_lo, zone_hi, order, memflags, d); /* Try getting a dirty buddy if we couldn't get a clean one. */ - if ( !pg && !(memflags & MEMF_no_scrub) ) + if ( !pg && !(memflags & MEMF_no_scrub) && + /* + * Allow any order unscrubbed allocations during boot time, we + * compensate by processing softirqs in the scrubbing loop below once + * irqs are enabled. + */ + (order <= dirty_max_order || system_state < SYS_STATE_active) ) pg = get_free_buddy(zone_lo, zone_hi, order, memflags | MEMF_no_scrub, d); if ( !pg ) @@ -XXX,XX +XXX,XX @@ static struct page_info *alloc_heap_pages( scrub_one_page(&pg[i], cold); dirty_cnt++; + + /* + * Use SYS_STATE_smp_boot explicitly; ahead of that state + * interrupts are disabled. + */ + if ( system_state == SYS_STATE_smp_boot && + !(dirty_cnt & 0xff) ) + process_pending_softirqs(); } else check_one_page(&pg[i]); -- 2.51.0 Hello, In XenServer we have seen the watchdog occasionally triggering during domain creation if 1GB pages are scrubbed in-place during physmap population. The following series attempt to mitigate this by adding preemption to page scrubbing in populate_physmap(). Also a new limit and command line option to signal the maximum allocation order when doing in-place scrubbing. This is set by default to CONFIG_PTDOM_MAX_ORDER. Thanks, Roger. Roger Pau Monne (3): xen/mm: enforce SCRUB_DEBUG checks for MEMF_no_scrub allocations xen/mm: allow deferred scrub of physmap populate allocated pages xen/mm: limit non-scrubbed allocations to a specific order docs/misc/xen-command-line.pandoc | 13 ++++ xen/common/domain.c | 28 +++++++++ xen/common/memory.c | 100 ++++++++++++++++++++++++++++-- xen/common/page_alloc.c | 30 +++++++-- xen/include/xen/mm.h | 14 +++++ xen/include/xen/sched.h | 5 ++ 6 files changed, 181 insertions(+), 9 deletions(-) -- 2.51.0 The logic in alloc_heap_pages() only checks for scrubbing pattern correctness when the caller doesn't pass MEMF_no_scrub in memflags. However already scrubbed pages can be checked for correctness, regardless of the caller having requested MEMF_no_scrub. Relax the checking around the check_one_page() call, to allow for calls with MEMF_no_scrub to also check the correctness of pages marked as already scrubbed when allocated. This widens the checking of scrubbing correctness, so it would also check the scrubbing correctness of MEMF_no_scrub allocations. Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> --- After discussing with Jan I've deliberately omitted the tag: Fixes: 0c5f2f9cefac ("mm: Make sure pages are scrubbed") The intended approach might have been to ensure the caller of alloc_heap_pages() gets properly scrubbed pages, rather than asserting the internal state of free pages is as expected. --- xen/common/page_alloc.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c index XXXXXXX..XXXXXXX 100644 --- a/xen/common/page_alloc.c +++ b/xen/common/page_alloc.c @@ -XXX,XX +XXX,XX @@ static struct page_info *alloc_heap_pages( spin_unlock(&heap_lock); - if ( first_dirty != INVALID_DIRTY_IDX || - (scrub_debug && !(memflags & MEMF_no_scrub)) ) + if ( first_dirty != INVALID_DIRTY_IDX || scrub_debug ) { bool cold = d && d != current->domain; @@ -XXX,XX +XXX,XX @@ static struct page_info *alloc_heap_pages( dirty_cnt++; } - else if ( !(memflags & MEMF_no_scrub) ) + else check_one_page(&pg[i]); } -- 2.51.0 Physmap population has the need to use pages as big as possible to reduce p2m shattering. However that triggers issues when big enough pages are not yet scrubbed, and so scrubbing must be done at allocation time. On some scenarios with added contention the watchdog can trigger: Watchdog timer detects that CPU55 is stuck! ----[ Xen-4.17.5-21 x86_64 debug=n Not tainted ]---- CPU: 55 RIP: e008:[<ffff82d040204c4a>] clear_page_sse2+0x1a/0x30 RFLAGS: 0000000000000202 CONTEXT: hypervisor (d0v12) [...] Xen call trace: [<ffff82d040204c4a>] R clear_page_sse2+0x1a/0x30 [<ffff82d04022a121>] S clear_domain_page+0x11/0x20 [<ffff82d04022c170>] S common/page_alloc.c#alloc_heap_pages+0x400/0x5a0 [<ffff82d04022d4a7>] S alloc_domheap_pages+0x67/0x180 [<ffff82d040226f9f>] S common/memory.c#populate_physmap+0x22f/0x3b0 [<ffff82d040228ec8>] S do_memory_op+0x728/0x1970 Introduce a mechanism to preempt page scrubbing in populate_physmap(). It relies on stashing the dirty page in the domain struct temporarily to preempt to guest context, so the scrubbing can resume when the domain re-enters the hypercall. The added deferral mechanism will only be used for domain construction, and is designed to be used with a single threaded domain builder. If the toolstack makes concurrent calls to XENMEM_populate_physmap for the same target domain it will trash stashed pages, resulting in slow domain physmap population. Note a similar issue is present in increase reservation. However that hypercall is likely to only be used once the domain is already running and the known implementations use 4K pages. It will be deal with in a separate patch using a different approach, that will also take care of the allocation in populate_physmap() once the domain is running. Fixes: 74d2e11ccfd2 ("mm: Scrub pages in alloc_heap_pages() if needed") Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> --- Changes since v2: - Introduce FREE_DOMHEAP_PAGE{,S}(). - Remove j local counter. - Free page pending scrub in domain_kill() also. - Remove BUG_ON(). - Reorder get_stashed_allocation() flow. - s/dirty/unscrubbed/ in a printk message. Changes since v1: - New in this version, different approach than v1. --- xen/common/domain.c | 28 ++++++++++++ xen/common/memory.c | 97 ++++++++++++++++++++++++++++++++++++++++- xen/common/page_alloc.c | 2 +- xen/include/xen/mm.h | 10 +++++ xen/include/xen/sched.h | 5 +++ 5 files changed, 140 insertions(+), 2 deletions(-) diff --git a/xen/common/domain.c b/xen/common/domain.c index XXXXXXX..XXXXXXX 100644 --- a/xen/common/domain.c +++ b/xen/common/domain.c @@ -XXX,XX +XXX,XX @@ static void _domain_destroy(struct domain *d) XVFREE(d->console); + if ( d->pending_scrub ) + { + FREE_DOMHEAP_PAGES(d->pending_scrub, d->pending_scrub_order); + d->pending_scrub_order = 0; + d->pending_scrub_index = 0; + } + argo_destroy(d); rangeset_domain_destroy(d); @@ -XXX,XX +XXX,XX @@ int domain_kill(struct domain *d) rspin_barrier(&d->domain_lock); argo_destroy(d); vnuma_destroy(d->vnuma); + /* + * Attempt to free any pages pending scrub early. Toolstack can still + * trigger populate_physmap() operations at this point, and hence a + * final cleanup must be done in _domain_destroy(). + */ + rspin_lock(&d->page_alloc_lock); + if ( d->pending_scrub ) + { + FREE_DOMHEAP_PAGES(d->pending_scrub, d->pending_scrub_order); + d->pending_scrub_order = 0; + d->pending_scrub_index = 0; + } + rspin_unlock(&d->page_alloc_lock); domain_set_outstanding_pages(d, 0); /* fallthrough */ case DOMDYING_dying: @@ -XXX,XX +XXX,XX @@ int domain_unpause_by_systemcontroller(struct domain *d) */ if ( new == 0 && !d->creation_finished ) { + if ( d->pending_scrub ) + { + printk(XENLOG_ERR + "%pd: cannot be started with pending unscrubbed pages, destroying\n", + d); + domain_crash(d); + return -EBUSY; + } d->creation_finished = true; arch_domain_creation_finished(d); } diff --git a/xen/common/memory.c b/xen/common/memory.c index XXXXXXX..XXXXXXX 100644 --- a/xen/common/memory.c +++ b/xen/common/memory.c @@ -XXX,XX +XXX,XX @@ static void increase_reservation(struct memop_args *a) a->nr_done = i; } +/* + * Temporary storage for a domain assigned page that's not been fully scrubbed. + * Stored pages must be domheap ones. + * + * The stashed page can be freed at any time by Xen, the caller must pass the + * order and NUMA node requirement to the fetch function to ensure the + * currently stashed page matches it's requirements. + */ +static void stash_allocation(struct domain *d, struct page_info *page, + unsigned int order, unsigned int scrub_index) +{ + rspin_lock(&d->page_alloc_lock); + + /* + * Drop any stashed allocation to accommodated the current one. This + * interface is designed to be used for single-threaded domain creation. + */ + if ( d->pending_scrub ) + free_domheap_pages(d->pending_scrub, d->pending_scrub_order); + + d->pending_scrub_index = scrub_index; + d->pending_scrub_order = order; + d->pending_scrub = page; + + rspin_unlock(&d->page_alloc_lock); +} + +static struct page_info *get_stashed_allocation(struct domain *d, + unsigned int order, + nodeid_t node, + unsigned int *scrub_index) +{ + struct page_info *page = NULL; + + rspin_lock(&d->page_alloc_lock); + + /* + * If there's a pending page to scrub check if it satisfies the current + * request. If it doesn't keep it stashed and return NULL. + */ + if ( d->pending_scrub && d->pending_scrub_order == order && + (node == NUMA_NO_NODE || node == page_to_nid(d->pending_scrub)) ) + { + page = d->pending_scrub; + *scrub_index = d->pending_scrub_index; + + /* + * The caller now owns the page, clear stashed information. Prevent + * concurrent usages of get_stashed_allocation() from returning the same + * page to different contexts. + */ + d->pending_scrub_index = 0; + d->pending_scrub_order = 0; + d->pending_scrub = NULL; + } + + rspin_unlock(&d->page_alloc_lock); + return page; +} + static void populate_physmap(struct memop_args *a) { struct page_info *page; @@ -XXX,XX +XXX,XX @@ static void populate_physmap(struct memop_args *a) } else { - page = alloc_domheap_pages(d, a->extent_order, a->memflags); + unsigned int scrub_start = 0; + nodeid_t node = + (a->memflags & MEMF_exact_node) ? MEMF_get_node(a->memflags) + : NUMA_NO_NODE; + + page = get_stashed_allocation(d, a->extent_order, node, + &scrub_start); + + if ( !page ) + page = alloc_domheap_pages(d, a->extent_order, + a->memflags | (d->creation_finished ? 0 + : MEMF_no_scrub)); if ( unlikely(!page) ) { @@ -XXX,XX +XXX,XX @@ static void populate_physmap(struct memop_args *a) goto out; } + if ( !d->creation_finished ) + { + unsigned int dirty_cnt = 0; + + /* Check if there's anything to scrub. */ + for ( j = scrub_start; j < (1U << a->extent_order); j++ ) + { + if ( !test_and_clear_bit(_PGC_need_scrub, + &page[j].count_info) ) + continue; + + scrub_one_page(&page[j], true); + + if ( (j + 1) != (1U << a->extent_order) && + !(++dirty_cnt & 0xff) && + hypercall_preempt_check() ) + { + a->preempted = 1; + stash_allocation(d, page, a->extent_order, ++j); + goto out; + } + } + } + if ( unlikely(a->memflags & MEMF_no_tlbflush) ) { for ( j = 0; j < (1U << a->extent_order); j++ ) diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c index XXXXXXX..XXXXXXX 100644 --- a/xen/common/page_alloc.c +++ b/xen/common/page_alloc.c @@ -XXX,XX +XXX,XX @@ static void page_list_add_scrub(struct page_info *pg, unsigned int node, # define scrub_page_cold clear_page_cold #endif -static void scrub_one_page(const struct page_info *pg, bool cold) +void scrub_one_page(const struct page_info *pg, bool cold) { void *ptr; diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h index XXXXXXX..XXXXXXX 100644 --- a/xen/include/xen/mm.h +++ b/xen/include/xen/mm.h @@ -XXX,XX +XXX,XX @@ unsigned long avail_node_heap_pages(unsigned int nodeid); #define alloc_domheap_page(d,f) (alloc_domheap_pages(d,0,f)) #define free_domheap_page(p) (free_domheap_pages(p,0)) +/* Free an allocation, and zero the pointer to it. */ +#define FREE_DOMHEAP_PAGES(p, o) do { \ + void *_ptr_ = (p); \ + (p) = NULL; \ + free_domheap_pages(_ptr_, o); \ +} while ( false ) +#define FREE_DOMHEAP_PAGE(p) FREE_DOMHEAP_PAGES(p, 0) + +void scrub_one_page(const struct page_info *pg, bool cold); + int online_page(mfn_t mfn, uint32_t *status); int offline_page(mfn_t mfn, int broken, uint32_t *status); int query_page_offline(mfn_t mfn, uint32_t *status); diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h index XXXXXXX..XXXXXXX 100644 --- a/xen/include/xen/sched.h +++ b/xen/include/xen/sched.h @@ -XXX,XX +XXX,XX @@ struct domain /* Pointer to console settings; NULL for system domains. */ struct domain_console *console; + + /* Pointer to allocated domheap page that possibly needs scrubbing. */ + struct page_info *pending_scrub; + unsigned int pending_scrub_order; + unsigned int pending_scrub_index; } __aligned(PAGE_SIZE); static inline struct page_list_head *page_to_list( -- 2.51.0 The current logic allows for up to 1G pages to be scrubbed in place, which can cause the watchdog to trigger in practice. Reduce the limit for in-place scrubbed allocations to a newly introduced define: CONFIG_DIRTY_MAX_ORDER. This currently defaults to CONFIG_PTDOM_MAX_ORDER on all architectures. Also introduce a command line option to set the value. Fixes: 74d2e11ccfd2 ("mm: Scrub pages in alloc_heap_pages() if needed") Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> --- Changes since v2: - Move placement of the max-order-dirty option help. - Add note in memop-max-order about interactions. - Use CONFIG_PTDOM_MAX_ORDER as the default. Changes since v1: - Split from previous patch. - Introduce a command line option to set the limit. --- docs/misc/xen-command-line.pandoc | 13 +++++++++++++ xen/common/memory.c | 3 --- xen/common/page_alloc.c | 23 ++++++++++++++++++++++- xen/include/xen/mm.h | 4 ++++ 4 files changed, 39 insertions(+), 4 deletions(-) diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc index XXXXXXX..XXXXXXX 100644 --- a/docs/misc/xen-command-line.pandoc +++ b/docs/misc/xen-command-line.pandoc @@ -XXX,XX +XXX,XX @@ presented as the number of bits needed to encode it. This must be at least one pending bit to be allocated. Defaults to 20 bits (to cover at most 1048576 interrupts). +### max-order-dirty +> `= <integer>` + +Specify the maximum allocation order allowed when scrubbing allocated pages +in-place. The allocation is non-preemptive, and hence the value must be keep +low enough to avoid hogging the CPU for too long. + +Defaults to `CONFIG_DIRTY_MAX_ORDER` or if unset to `CONFIG_PTDOM_MAX_ORDER`. +Note those are internal per-architecture defines not available from Kconfig. + ### mce (x86) > `= <boolean>` @@ -XXX,XX +XXX,XX @@ requests issued by the various kinds of domains (in this order: ordinary DomU, control domain, hardware domain, and - when supported by the platform - DomU with pass-through device assigned). +Note orders here can be further limited by the value in `max-order-dirty` for +allocations requesting pages to be scrubbed in-place. + ### mmcfg (x86) > `= <boolean>[,amd-fam10]` diff --git a/xen/common/memory.c b/xen/common/memory.c index XXXXXXX..XXXXXXX 100644 --- a/xen/common/memory.c +++ b/xen/common/memory.c @@ -XXX,XX +XXX,XX @@ struct memop_args { #ifndef CONFIG_CTLDOM_MAX_ORDER #define CONFIG_CTLDOM_MAX_ORDER CONFIG_PAGEALLOC_MAX_ORDER #endif -#ifndef CONFIG_PTDOM_MAX_ORDER -#define CONFIG_PTDOM_MAX_ORDER CONFIG_HWDOM_MAX_ORDER -#endif static unsigned int __read_mostly domu_max_order = CONFIG_DOMU_MAX_ORDER; static unsigned int __read_mostly ctldom_max_order = CONFIG_CTLDOM_MAX_ORDER; diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c index XXXXXXX..XXXXXXX 100644 --- a/xen/common/page_alloc.c +++ b/xen/common/page_alloc.c @@ -XXX,XX +XXX,XX @@ static PAGE_LIST_HEAD(page_offlined_list); /* Broken page list, protected by heap_lock. */ static PAGE_LIST_HEAD(page_broken_list); +/* Maximum order allowed for allocations with MEMF_no_scrub. */ +#ifndef CONFIG_DIRTY_MAX_ORDER +# define CONFIG_DIRTY_MAX_ORDER CONFIG_PTDOM_MAX_ORDER +#endif +static unsigned int __ro_after_init dirty_max_order = CONFIG_DIRTY_MAX_ORDER; +integer_param("max-order-dirty", dirty_max_order); + /************************* * BOOT-TIME ALLOCATOR */ @@ -XXX,XX +XXX,XX @@ static struct page_info *alloc_heap_pages( pg = get_free_buddy(zone_lo, zone_hi, order, memflags, d); /* Try getting a dirty buddy if we couldn't get a clean one. */ - if ( !pg && !(memflags & MEMF_no_scrub) ) + if ( !pg && !(memflags & MEMF_no_scrub) && + /* + * Allow any order unscrubbed allocations during boot time, we + * compensate by processing softirqs in the scrubbing loop below once + * irqs are enabled. + */ + (order <= dirty_max_order || system_state < SYS_STATE_active) ) pg = get_free_buddy(zone_lo, zone_hi, order, memflags | MEMF_no_scrub, d); if ( !pg ) @@ -XXX,XX +XXX,XX @@ static struct page_info *alloc_heap_pages( scrub_one_page(&pg[i], cold); dirty_cnt++; + + /* + * Use SYS_STATE_smp_boot explicitly; ahead of that state + * interrupts are disabled. + */ + if ( system_state == SYS_STATE_smp_boot && + !(dirty_cnt & 0xff) ) + process_pending_softirqs(); } else check_one_page(&pg[i]); diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h index XXXXXXX..XXXXXXX 100644 --- a/xen/include/xen/mm.h +++ b/xen/include/xen/mm.h @@ -XXX,XX +XXX,XX @@ struct npfec { #else #define MAX_ORDER 20 /* 2^20 contiguous pages */ #endif +#ifndef CONFIG_PTDOM_MAX_ORDER +# define CONFIG_PTDOM_MAX_ORDER CONFIG_HWDOM_MAX_ORDER +#endif + mfn_t acquire_reserved_page(struct domain *d, unsigned int memflags); /* Private domain structs for DOMID_XEN, DOMID_IO, etc. */ -- 2.51.0