[RFC v2 10/43] PKRAM: pass a list of preserved ranges to the next kernel
Anthony Yznaga
anthony.yznaga at oracle.com
Tue Mar 30 22:35:45 BST 2021
In order to build a new memblock reserved list during boot that
includes ranges preserved by the previous kernel, a list of preserved
ranges is passed to the next kernel via the pkram superblock. The
ranges are stored in ascending order in a linked list of pages. A more
complete memblock list is not prepared to avoid possible conflicts with
changes in a newer kernel and to avoid having to allocate a contiguous
range larger than a page.
Signed-off-by: Anthony Yznaga <anthony.yznaga at oracle.com>
---
mm/pkram.c | 183 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 176 insertions(+), 7 deletions(-)
diff --git a/mm/pkram.c b/mm/pkram.c
index a9e6cd8ca084..4cfa236a4126 100644
--- a/mm/pkram.c
+++ b/mm/pkram.c
@@ -86,6 +86,20 @@ struct pkram_node {
#define PKRAM_LOAD 2
#define PKRAM_ACCMODE_MASK 3
+struct pkram_region {
+ phys_addr_t base;
+ phys_addr_t size;
+};
+
+struct pkram_region_list {
+ __u64 prev_pfn;
+ __u64 next_pfn;
+
+ struct pkram_region regions[0];
+};
+
+#define PKRAM_REGIONS_LIST_MAX \
+ ((PAGE_SIZE-sizeof(struct pkram_region_list))/sizeof(struct pkram_region))
/*
* The PKRAM super block contains data needed to restore the preserved memory
* structure on boot. The pointer to it (pfn) should be passed via the 'pkram'
@@ -98,13 +112,20 @@ struct pkram_node {
*/
struct pkram_super_block {
__u64 node_pfn; /* first element of the node list */
+ __u64 region_list_pfn;
+ __u64 nr_regions;
};
+static struct pkram_region_list *pkram_regions_list;
+static int pkram_init_regions_list(void);
+static unsigned long pkram_populate_regions_list(void);
+
static unsigned long pkram_sb_pfn __initdata;
static struct pkram_super_block *pkram_sb;
extern int pkram_add_identity_map(struct page *page);
extern void pkram_remove_identity_map(struct page *page);
+extern void pkram_find_preserved(unsigned long start, unsigned long end, void *private, int (*callback)(unsigned long base, unsigned long size, void *private));
/*
* For convenience sake PKRAM nodes are kept in an auxiliary doubly-linked list
@@ -862,21 +883,48 @@ static void __pkram_reboot(void)
struct page *page;
struct pkram_node *node;
unsigned long node_pfn = 0;
+ unsigned long rl_pfn = 0;
+ unsigned long nr_regions = 0;
+ int err = 0;
- list_for_each_entry_reverse(page, &pkram_nodes, lru) {
- node = page_address(page);
- if (WARN_ON(node->flags & PKRAM_ACCMODE_MASK))
- continue;
- node->node_pfn = node_pfn;
- node_pfn = page_to_pfn(page);
+ if (!list_empty(&pkram_nodes)) {
+ err = pkram_add_identity_map(virt_to_page(pkram_sb));
+ if (err) {
+ pr_err("PKRAM: failed to add super block to pagetable\n");
+ goto done;
+ }
+ list_for_each_entry_reverse(page, &pkram_nodes, lru) {
+ node = page_address(page);
+ if (WARN_ON(node->flags & PKRAM_ACCMODE_MASK))
+ continue;
+ node->node_pfn = node_pfn;
+ node_pfn = page_to_pfn(page);
+ }
+ err = pkram_init_regions_list();
+ if (err) {
+ pr_err("PKRAM: failed to init regions list\n");
+ goto done;
+ }
+ nr_regions = pkram_populate_regions_list();
+ if (IS_ERR_VALUE(nr_regions)) {
+ err = nr_regions;
+ pr_err("PKRAM: failed to populate regions list\n");
+ goto done;
+ }
+ rl_pfn = page_to_pfn(virt_to_page(pkram_regions_list));
}
+done:
/*
* Zero out pkram_sb completely since it may have been passed from
* the previous boot.
*/
memset(pkram_sb, 0, PAGE_SIZE);
- pkram_sb->node_pfn = node_pfn;
+ if (!err && node_pfn) {
+ pkram_sb->node_pfn = node_pfn;
+ pkram_sb->region_list_pfn = rl_pfn;
+ pkram_sb->nr_regions = nr_regions;
+ }
}
static int pkram_reboot(struct notifier_block *notifier,
@@ -952,3 +1000,124 @@ static int __init pkram_init(void)
return 0;
}
module_init(pkram_init);
+
+static int count_region_cb(unsigned long base, unsigned long size, void *private)
+{
+ unsigned long *nr_regions = (unsigned long *)private;
+
+ (*nr_regions)++;
+ return 0;
+}
+
+static unsigned long pkram_count_regions(void)
+{
+ unsigned long nr_regions = 0;
+
+ pkram_find_preserved(0, PHYS_ADDR_MAX, &nr_regions, count_region_cb);
+
+ return nr_regions;
+}
+
+/*
+ * To faciliate rapidly building a new memblock reserved list during boot
+ * with the addition of preserved memory ranges a regions list is built
+ * before reboot.
+ * The regions list is a linked list of pages with each page containing an
+ * array of preserved memory ranges. The ranges are stored in each page
+ * and across the list in address order. A linked list is used rather than
+ * a single contiguous range to mitigate against the possibility that a
+ * larger, contiguous allocation may fail due to fragmentation.
+ *
+ * Since the pages of the regions list must be preserved and the pkram
+ * pagetable is used to determine what ranges are preserved, the list pages
+ * must be allocated and represented in the pkram pagetable before they can
+ * be populated. Rather than recounting the number of regions after
+ * allocating pages and repeating until a precise number of pages are
+ * are allocated, the number of pages needed is estimated.
+ */
+static int pkram_init_regions_list(void)
+{
+ struct pkram_region_list *rl;
+ unsigned long nr_regions;
+ unsigned long nr_lpages;
+ struct page *page;
+
+ nr_regions = pkram_count_regions();
+
+ nr_lpages = DIV_ROUND_UP(nr_regions, PKRAM_REGIONS_LIST_MAX);
+ nr_regions += nr_lpages;
+ nr_lpages = DIV_ROUND_UP(nr_regions, PKRAM_REGIONS_LIST_MAX);
+
+ for (; nr_lpages; nr_lpages--) {
+ page = pkram_alloc_page(GFP_KERNEL | __GFP_ZERO);
+ if (!page)
+ return -ENOMEM;
+ rl = page_address(page);
+ if (pkram_regions_list) {
+ rl->next_pfn = page_to_pfn(virt_to_page(pkram_regions_list));
+ pkram_regions_list->prev_pfn = page_to_pfn(page);
+ }
+ pkram_regions_list = rl;
+ }
+
+ return 0;
+}
+
+struct pkram_regions_priv {
+ struct pkram_region_list *curr;
+ struct pkram_region_list *last;
+ unsigned long nr_regions;
+ int idx;
+};
+
+static int add_region_cb(unsigned long base, unsigned long size, void *private)
+{
+ struct pkram_regions_priv *priv;
+ struct pkram_region_list *rl;
+ int i;
+
+ priv = (struct pkram_regions_priv *)private;
+ rl = priv->curr;
+ i = priv->idx;
+
+ if (!rl) {
+ WARN_ON(1);
+ return 1;
+ }
+
+ if (!i)
+ priv->last = priv->curr;
+
+ rl->regions[i].base = base;
+ rl->regions[i].size = size;
+
+ priv->nr_regions++;
+ i++;
+ if (i == PKRAM_REGIONS_LIST_MAX) {
+ u64 next_pfn = rl->next_pfn;
+
+ if (next_pfn)
+ priv->curr = pfn_to_kaddr(next_pfn);
+ else
+ priv->curr = NULL;
+
+ i = 0;
+ }
+ priv->idx = i;
+
+ return 0;
+}
+
+static unsigned long pkram_populate_regions_list(void)
+{
+ struct pkram_regions_priv priv = { .curr = pkram_regions_list };
+
+ pkram_find_preserved(0, PHYS_ADDR_MAX, &priv, add_region_cb);
+
+ /*
+ * Link the first node to the last populated one.
+ */
+ pkram_regions_list->prev_pfn = page_to_pfn(virt_to_page(priv.last));
+
+ return priv.nr_regions;
+}
--
1.8.3.1
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