Re: [Qemu-devel] Re: [PATCH v3 2/6] Introduce bit-based phys_ram_dirty for VGA, CODE, MIGRATION and MASTER.

[Yoshiaki Tamura]

2010/4/19 Yoshiaki Tamura <address@hidden>:
> Avi Kivity wrote:
>>
>> On 04/19/2010 12:43 PM, Yoshiaki Tamura wrote:
>>>
>>> Replaces byte-based phys_ram_dirty bitmap with four bit-based
>>> phys_ram_dirty
>>> bitmap. On allocation, it sets all bits in the bitmap.
>>>
>>> Signed-off-by: Yoshiaki Tamura<address@hidden>
>>> ---
>>> exec.c | 16 +++++++++++-----
>>> qemu-common.h | 3 +++
>>> 2 files changed, 14 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/exec.c b/exec.c
>>> index c74b0a4..b85cb26 100644
>>> --- a/exec.c
>>> +++ b/exec.c
>>> @@ -110,7 +110,7 @@ uint8_t *code_gen_ptr;
>>>
>>> #if !defined(CONFIG_USER_ONLY)
>>> int phys_ram_fd;
>>> -uint8_t *phys_ram_dirty;
>>> +unsigned long *phys_ram_dirty[NUM_DIRTY_IDX];
>>> static int in_migration;
>>>
>>> typedef struct RAMBlock {
>>> @@ -2825,10 +2825,16 @@ ram_addr_t qemu_ram_alloc(ram_addr_t size)
>>> new_block->next = ram_blocks;
>>> ram_blocks = new_block;
>>>
>>> - phys_ram_dirty = qemu_realloc(phys_ram_dirty,
>>> - (last_ram_offset + size)>> TARGET_PAGE_BITS);
>>> - memset(phys_ram_dirty + (last_ram_offset>> TARGET_PAGE_BITS),
>>> - 0xff, size>> TARGET_PAGE_BITS);
>>> + if (BITMAP_SIZE(last_ram_offset + size) !=
>>> BITMAP_SIZE(last_ram_offset)) {
>>
>> This check is unneeded - the code will work fine even if the bitmap size
>> doesn't change.
>
> OK.  I'll remove it.

I have a problem here.
If I remove this check, glibc reports an error as below.

*** glibc detected *** /usr/local/qemu/bin/qemu-system-x86_64:
realloc(): invalid pointer: 0x0000000001f0e450 ***
======= Backtrace: =========
/lib64/libc.so.6[0x369fa75a96]
/lib64/libc.so.6(realloc+0x2a1)[0x369fa7b881]
/usr/local/qemu/bin/qemu-system-x86_64[0x437d93]
/usr/local/qemu/bin/qemu-system-x86_64[0x4f03f6]
/usr/local/qemu/bin/qemu-system-x86_64[0x5b052c]
/usr/local/qemu/bin/qemu-system-x86_64[0x5b0d8b]
/usr/local/qemu/bin/qemu-system-x86_64[0x41ec2b]
/lib64/libc.so.6(__libc_start_main+0xfd)[0x369fa1ea2d]
/usr/local/qemu/bin/qemu-system-x86_64[0x406479]
======= Memory map: ========

I reminded that I put this check to avoid reallocating same size to the bitmap.
qemu goes this routine at start up, and extends last_ram_offset at
small numbers.
The error above is reported at the extension phase.

Is this happening only on my environment (Fedora 11 x86_64)?

>>> + int i;
>>> + for (i = MASTER_DIRTY_IDX; i< NUM_DIRTY_IDX; i++) {
>>> + phys_ram_dirty[i]
>>> + = qemu_realloc(phys_ram_dirty[i],
>>> + BITMAP_SIZE(last_ram_offset + size));
>>> + memset((uint8_t *)phys_ram_dirty[i] +
>>> + BITMAP_SIZE(last_ram_offset), 0xff, BITMAP_SIZE(size));
>>> + }
>>> + }
>>>
>>> last_ram_offset += size;
>>>
>>
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