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Re: [Qemu-devel] [PATCH] migration: catch unknown flags in ram_load
From: |
Peter Lieven |
Subject: |
Re: [Qemu-devel] [PATCH] migration: catch unknown flags in ram_load |
Date: |
Mon, 12 May 2014 12:25:23 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 |
Am 12.05.2014 12:19, schrieb Juan Quintela:
> Peter Lieven <address@hidden> wrote:
>> if a saved vm has unknown flags in the memory data qemu
>> currently simply ignores this flag and continues which
>> yields in an unpredictable result.
>>
>> this patch catches all unknown flags and
>> aborts the loading of the vm.
>>
>> CC: address@hidden
>> Signed-off-by: Peter Lieven <address@hidden>
> .....
>
> Once here, shouldn't be better to do this as:
>
> change do {} while () for while (true) {}
>
>>
>> @@ -1121,6 +1119,9 @@ static int ram_load(QEMUFile *f, void *opaque, int
>> version_id)
>> }
>> } else if (flags & RAM_SAVE_FLAG_HOOK) {
>> ram_control_load_hook(f, flags);
>> + } else if (!(flags & RAM_SAVE_FLAG_EOS)) {
>> + ret = -EINVAL;
>> + goto done;
>> }
>> error = qemu_file_get_error(f);
>> if (error) {
>
> } else if (flags & RAM_SAVE_FLAG_HOOK) {
> ram_control_load_hook(f, flags);
> + } else if (flags & RAM_SAVE_FLAG_EOS) {
> + break;
> + } else {
> + ret = -EINVAL;
> + goto done;
> }
> error = qemu_file_get_error(f);
> if (error) {
> }
>
>
> This way, we are checking RAM_SAVE_FLAG_EOS the same way than any other
> flag? And we don't have to duplicate the FLAG_NAME?
Ok, I will send a v2.
>
> Unrelated to this patch, all the flags are a bitmap, but really, the
> ones that can be together are RAM_SAVE_FLAG_CONTINUE and the rest, all
> the others need to be alone. I am telling this because we have used
> already 8 flags, and we are using the low bits of offset to save the
> flags, we have 10 flags? Perhaps changing the last flag to mean that
> the low bits pass to be a counter?
Some better encoding would indeed be useful. I already thought
that we might run out of flags soon. We have 11 flags I think,
but there is not much space left. Reserving the last flag to indicate
that the lower 10 bits a are counter might be a good option.
Peter
>
> PD. No, I haven't investigated right now how RAM_SAVE_FLAG_HOOK works
> with all of this.
>
> Later, Juan.
>