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SubjectRe: kvm kdump regression
Hello,

I was slightly confused with the debug patch but it looks like someone
is feeding non-percpu address to the function. Hmm... or it could be
that the first chunk test is returning false incorrectly for an
address which is inside static percpu area. Can you please try the
following patch instead? This should make the problem go away and
give us enough information about which address is causing the problem.
Please attach logs from both the original kernel before triggering
crash and from the crash kernel.

Thank you.

diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c
index 7d9c1d0..357569a 100644
--- a/mm/percpu-vm.c
+++ b/mm/percpu-vm.c
@@ -415,6 +415,7 @@ static struct pcpu_chunk *pcpu_create_chunk(void)
{
struct pcpu_chunk *chunk;
struct vm_struct **vms;
+ int i;

chunk = pcpu_alloc_chunk();
if (!chunk)
@@ -429,6 +430,13 @@ static struct pcpu_chunk *pcpu_create_chunk(void)

chunk->data = vms;
chunk->base_addr = vms[0]->addr - pcpu_group_offsets[0];
+ chunk->chunkno = ++chunkno;
+ printk("XXX chunk %d allocated base_addr=%p\n",
+ chunk->chunkno, chunk->base_addr);
+ printk("XXX VMS:");
+ for (i = 0; i < pcpu_nr_groups; i++)
+ printk(" %zu@%p", vms[i]->size, vms[i]->addr);
+ printk("\n");
return chunk;
}

diff --git a/mm/percpu.c b/mm/percpu.c
index 77e3f5a..14c836b 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -96,7 +96,10 @@
#define __pcpu_ptr_to_addr(ptr) (void __force *)(ptr)
#endif /* CONFIG_SMP */

+static int chunkno;
+
struct pcpu_chunk {
+ int chunkno;
struct list_head list; /* linked to pcpu_slot lists */
int free_size; /* free bytes in the chunk */
int contig_hint; /* max contiguous size hint */
@@ -182,6 +185,40 @@ static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */
static void pcpu_reclaim(struct work_struct *work);
static DECLARE_WORK(pcpu_reclaim_work, pcpu_reclaim);

+void pcpu_dump_chunk(struct pcpu_chunk *chunk)
+{
+ int i, contig = 0, free = 0;
+
+ printk("XXX %d(f=%d,c=%d,u=%d,a=%d)", chunk->chunkno,
+ chunk->free_size, chunk->contig_hint,
+ chunk->map_used, chunk->map_alloc);
+ for (i = 0; i < chunk->map_used; i++) {
+ if (chunk->map[i] > 0) {
+ free += chunk->map[i];
+ contig = max(contig, chunk->map[i]);
+ }
+ printk(" %d", chunk->map[i]);
+ }
+ printk(" free=%d contig=%d%s\n", free, contig,
+ (free != chunk->free_size || contig != chunk->contig_hint) ?
+ " MISMATCH!" : "");
+}
+
+void pcpu_dump_chunk_slots(void)
+{
+ struct pcpu_chunk *chunk;
+ int i;
+
+ printk("XXX percpu allocator dump\n");
+ for (i = 0; i < pcpu_nr_slots; i++) {
+ if (list_empty(&pcpu_slot[i]))
+ continue;
+ printk("XXX SLOT[%02d]\n", i);
+ list_for_each_entry(chunk, &pcpu_slot[i], list)
+ pcpu_dump_chunk(chunk);
+ }
+}
+
static bool pcpu_addr_in_first_chunk(void *addr)
{
void *first_start = pcpu_first_chunk->base_addr;
@@ -1017,8 +1054,20 @@ phys_addr_t per_cpu_ptr_to_phys(void *addr)
return __pa(addr);
else
return page_to_phys(vmalloc_to_page(addr));
- } else
+ } else {
+ if ((unsigned long)addr < VMALLOC_START ||
+ (unsigned long)addr >= VMALLOC_END) {
+ static bool first = true;
+ if (first) {
+ WARN_ON(1);
+ printk("XXX addr=%p out of vmalloc area and not in first chunk\n", addr);
+ pcpu_dump_chunk_slots();
+ first = false;
+ }
+ return __pa(addr);
+ }
return page_to_phys(pcpu_addr_to_page(addr));
+ }
}

/**
@@ -1283,6 +1332,11 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
pcpu_chunk_struct_size = sizeof(struct pcpu_chunk) +
BITS_TO_LONGS(pcpu_unit_pages) * sizeof(unsigned long);

+ printk("XXX CPU->UNIT M/O");
+ for_each_possible_cpu(cpu)
+ printk(" %d:%lx", unit_map[cpu], unit_off[cpu]);
+ printk("\n");
+
/*
* Allocate chunk slots. The additional last slot is for
* empty chunks.
@@ -1292,6 +1346,10 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
for (i = 0; i < pcpu_nr_slots; i++)
INIT_LIST_HEAD(&pcpu_slot[i]);

+ printk("XXX ss=%zu up=%d us=%d ns=%d rs=%zd ds=%zd\n",
+ ai->static_size, pcpu_unit_pages, pcpu_unit_size,
+ pcpu_nr_slots, ai->reserved_size, dyn_size);
+
/*
* Initialize static chunk. If reserved_size is zero, the
* static chunk covers static area + dynamic allocation area
@@ -1311,6 +1369,7 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
schunk->free_size = ai->reserved_size;
pcpu_reserved_chunk = schunk;
pcpu_reserved_chunk_limit = ai->static_size + ai->reserved_size;
+ schunk->chunkno = -1;
} else {
schunk->free_size = dyn_size;
dyn_size = 0; /* dynamic area covered */
@@ -1340,6 +1399,12 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
pcpu_first_chunk = dchunk ?: schunk;
pcpu_chunk_relocate(pcpu_first_chunk, -1);

+ if (pcpu_reserved_chunk) {
+ printk("XXX reserved chunk\n");
+ pcpu_dump_chunk(pcpu_reserved_chunk);
+ }
+ pcpu_dump_chunk_slots();
+
/* we're done */
pcpu_base_addr = base_addr;
return 0;
@@ -1623,6 +1688,7 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
goto out_free_areas;
}
areas[group] = ptr;
+ printk("XXX areas[%d]=%p\n", group, areas[group]);

base = min(ptr, base);

@@ -1639,12 +1705,15 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
}

/* base address is now known, determine group base offsets */
+ printk("XXX base_addr=%p", base);
max_distance = 0;
for (group = 0; group < ai->nr_groups; group++) {
ai->groups[group].base_offset = areas[group] - base;
max_distance = max_t(size_t, max_distance,
ai->groups[group].base_offset);
+ printk(" %lx", ai->groups[group].base_offset);
}
+ printk("\n");
max_distance += ai->unit_size;

/* warn if maximum distance is further than 75% of vmalloc space */

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