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Re: [Qemu-devel] NVDIMM live migration broken?
From: |
Juan Quintela |
Subject: |
Re: [Qemu-devel] NVDIMM live migration broken? |
Date: |
Tue, 27 Jun 2017 18:58:12 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux) |
Haozhong Zhang <address@hidden> wrote:
....
Hi
I am trying to see what is going on.
>>
>
> I managed to reproduce this bug. After bisect between good v2.8.0 and
> bad edf8bc984, it looks a regression introduced by
> 6b6712efccd "ram: Split dirty bitmap by RAMBlock"
> This commit may result in guest crash after migration if any host
> memory backend is used.
>
> Could you test whether the attached draft patch fixes this bug? If yes,
> I will make a formal patch later.
>
> Thanks,
> Haozhong
>
> diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
> index 73d1bea8b6..2ae4ff3965 100644
> --- a/include/exec/ram_addr.h
> +++ b/include/exec/ram_addr.h
> @@ -377,7 +377,9 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock
> *rb,
> uint64_t *real_dirty_pages)
> {
> ram_addr_t addr;
> + ram_addr_t offset = rb->offset;
> unsigned long page = BIT_WORD(start >> TARGET_PAGE_BITS);
> + unsigned long dirty_page = BIT_WORD((start + offset) >>
> TARGET_PAGE_BITS);
> uint64_t num_dirty = 0;
> unsigned long *dest = rb->bmap;
>
If this is the case, I can't understand how it ever worked :-(
Investigating.
Later, Juan.
> @@ -386,8 +388,9 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock
> *rb,
> int k;
> int nr = BITS_TO_LONGS(length >> TARGET_PAGE_BITS);
> unsigned long * const *src;
> - unsigned long idx = (page * BITS_PER_LONG) / DIRTY_MEMORY_BLOCK_SIZE;
> - unsigned long offset = BIT_WORD((page * BITS_PER_LONG) %
> + unsigned long idx = (dirty_page * BITS_PER_LONG) /
> + DIRTY_MEMORY_BLOCK_SIZE;
> + unsigned long offset = BIT_WORD((dirty_page * BITS_PER_LONG) %
> DIRTY_MEMORY_BLOCK_SIZE);
>
> rcu_read_lock();
> @@ -416,7 +419,7 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock
> *rb,
> } else {
> for (addr = 0; addr < length; addr += TARGET_PAGE_SIZE) {
> if (cpu_physical_memory_test_and_clear_dirty(
> - start + addr,
> + start + addr + offset,
> TARGET_PAGE_SIZE,
> DIRTY_MEMORY_MIGRATION)) {
> *real_dirty_pages += 1;