Re: [Qemu-devel] KVM call agenda for tuesday 31

[Andreas Färber]

Am 09.02.2012 23:37, schrieb Anthony Liguori:
> On 02/09/2012 04:23 PM, Peter Maydell wrote:
>> Ping re the VMState and variable sized arrays issue. I don't
>> see any consensus in this discussion for a different approach,
>> so should we just commit Mitsyanko's patchset?
> 
> I don't know if I mentioned this, but do we really need variable sizes?

You didn't in this context. :)

I didn't write the original code so don't know what use cases beyond
ICH9 it had in mind. Alex?

> Can we just use a fixed size (pre-allocated) array and then use a
> VMSTATE_SUB_ARRAY?

my RFC did something similar. Apparently I forgot the link:

http://patchwork.ozlabs.org/patch/133065/

In the case of AHCI allocating 32 structs when we know we only need six
seems like a waste - although I agree that preallocation can be a good
thing (but that's for a different thread).

> If it's truly variable size with no upper bound, then that's actually a
> security problem since it implies a guest can do unbounded memory
> allocation.

In the cases we're talking about here, I believe the allocation is
always in the init or realize phase based on user parameters, not the guest.

And whatever we decide, we definitely need better documentation on
VMState! There's also a small part that wasn't moved to vmstate.h. I'd
volunteer for the easy macros but honestly don't understand all of them.

Andreas

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