[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH v2 1/7] exec: Fix for qemu_ram_resize() callback

From: David Hildenbrand
Subject: Re: [PATCH v2 1/7] exec: Fix for qemu_ram_resize() callback
Date: Thu, 6 Feb 2020 15:54:52 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1

On 06.02.20 12:28, Shameerali Kolothum Thodi wrote:
>> -----Original Message-----
>> From: David Hildenbrand [mailto:address@hidden]
>> Sent: 06 February 2020 10:56
>> To: Shameerali Kolothum Thodi <address@hidden>;
>> Igor Mammedov <address@hidden>
>> Cc: address@hidden; address@hidden;
>> address@hidden; address@hidden; address@hidden;
>> xuwei (O) <address@hidden>; Linuxarm <address@hidden>;
>> address@hidden; address@hidden; address@hidden
>> Subject: Re: [PATCH v2 1/7] exec: Fix for qemu_ram_resize() callback
> [...]
>>> root@ubuntu:/# cat /dev/pmem
>>> pmem0  pmem1
>>> From the logs, it looks like the ram_load_precopy() --> qemu_ram_resize() is
>> not
>>> called as length == used_length and both seems to be page aligned values.
>>> And from
>> https://github.com/qemu/qemu/blob/master/migration/ram.c#L3421
>>> qemu_ram_resize() is called with length if length != used_length.
>> Assume on your source, the old size is 12345 bytes. So 16384 aligned up
>> (4 pages).
>> Assume on your target, the new size is 123456 bytes, so 126976 aligned
>> up (31 pages).
>> If you migrate from source to destination, the migration code would
>> resize to 16384, although the "actual size" is 12345. The callback will
>> be called with the aligned size, not the actual size. Same the other way
>> around. That's what's inconsistent IMHO.
> Thanks. You are right. I didn’t consider the case where the target can be
> configured with a larger number of devices than the source. I can replicate
> the scenario now,
> Source:
> fw_cfg_add_file_callback: filename etc/boot-fail-wait size 0x4
> fw_cfg_add_file_callback: filename etc/acpi/nvdimm-mem size 0x1000
> fw_cfg_add_file_callback: filename etc/acpi/tables size 0x6210
> Target:
> ram_load_precopy: Ram blk mem1 length 0x40000000 used_length 0x40000000
> ram_load_precopy: Ram blk virt.flash0 length 0x4000000 used_length 0x4000000
> ram_load_precopy: Ram blk virt.flash1 length 0x4000000 used_length 0x4000000
> ram_load_precopy: Ram blk /rom@etc/acpi/tables length 0x7000 used_length 
> 0x8000
> fw_cfg_modify_file: filename etc/acpi/tables len 0x7000
> Target updates FWCfgEntry with a page aligned size :(. I will look into this 
> and see how
> we can solve this. Any pointers welcome.

Can you look the original value up somehow and us the resize callback
only as a notification that something changed? (that value would have to
be stored somewhere and migrated I assume - maybe that's already being done)


David / dhildenb

reply via email to

[Prev in Thread] Current Thread [Next in Thread]