Re: [PATCH v1 01/14] s390x/s390-virtio-ccw: don't crash on weird RAM sizes

[David Hildenbrand <david@redhat.com>]

On 11.09.24 14:46, Thomas Huth wrote:
> On 11/09/2024 14.38, David Hildenbrand wrote:
>> On 11.09.24 13:28, Janosch Frank wrote:
>>> On 9/10/24 7:57 PM, David Hildenbrand wrote:
>>>> KVM is not happy when starting a VM with weird RAM sizes:
>>>>
>>>>      # qemu-system-s390x --enable-kvm --nographic -m 1234K
>>>>      qemu-system-s390x: kvm_set_user_memory_region:
>>>> KVM_SET_USER_MEMORY_REGION
>>>>        failed, slot=0, start=0x0, size=0x244000: Invalid argument
>>>>      kvm_set_phys_mem: error registering slot: Invalid argument
>>>>      Aborted (core dumped)
>>>>
>>>> Let's handle that in a better way by rejecting such weird RAM sizes
>>>> right from the start:
>>>>
>>>
>>> Huh, I always assumed that ram is handled in multiples of 1MB in QEMU.
>>
>> Me as well, I did not dig if that changed at some point ... or why such odd
>> sizes would even be required :)
> 
> I guess it's there for some old PC hardware ... Remember, 640K ought to be
> enough for anybody.

True, maybe the "default to MiB" made some of us believe that something
smaller is impossible :)

And in fact, I think suffix support was added in

commit 6e1d3c1c855818a6d1399698572afae0d11b872b
Author: Igor Mammedov <imammedo@redhat.com>
Date:   Wed Nov 27 01:27:35 2013 +0100

     vl: convert -m to QemuOpts
     
     Adds option to -m
      "size" - startup memory amount
     
     For compatibility with legacy CLI if suffix-less number is passed,
     it assumes amount in Mb.
     
     Otherwise user is free to use suffixed number using suffixes b,k/K,M,G


-- 
Cheers,

David / dhildenb