Re: [Qemu-devel] [PATCH 3/5] pc: future-proof migration-compatibility of ACPI tables

[Paolo Bonzini <pbonzini@redhat.com>]

Il 28/07/2014 17:59, Michael S. Tsirkin ha scritto:
> On Mon, Jul 28, 2014 at 05:34:16PM +0200, Paolo Bonzini wrote:
>> This patch avoids that similar changes break QEMU again in the future.
>> QEMU will now hard-code 64k as the maximum ACPI table size, which
>> (despite being an order of magnitude smaller than 640k) should be enough
>> for everyone.
> 
> Famous last words :) So what worries me here, is that we
> are potentially breaking legal configurations for the
> benefit of the minority that cares about cross-version
> migration.
> 
> So I'm inclined to apply everything except this patch, and
> instead, use the patches that I sent to make the
> ram block very large, something like 1 Megabyte.

Even just 128k are enough for 160 VCPUs, 255 memory slots and 35-40 PCI
bridges.  And for 2.2 I'd rather move to the other model where all
user-defined elements (MADT, SSDT) are in a separate file and we
guarantee that *all* changes are versioned by machine type.

What do you think about just changing 64k->128k?  Your patch is a huge
amount of code for -rc4.

Paolo