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Date: Fri, 22 Dec 2017 11:57:34 +0100
From: Cornelia Huck <cohuck@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v1 0/2] s390x/tcg: TEST PROTECTION and
 memory hotplug
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To: David Hildenbrand <david@redhat.com>
Cc: qemu-s390x@nongnu.org, qemu-devel@nongnu.org, Christian Borntraeger <borntraeger@de.ibm.com>, Richard Henderson <rth@twiddle.net>, Alexander Graf <agraf@suse.de>

On Mon, 18 Dec 2017 23:46:14 +0100
David Hildenbrand <david@redhat.com> wrote:

> While trying to fix TCG so I can properly detect memory in kvm-unit-tests
> ... looks like I accidentally made memory hotplug under TCG work (whoops).

:)

> 
> qemu-system-s390x ... -m 2048,maxmem=4096M,slots=4 ...
> 
> [root@localhost ~]# cat /proc/meminfo
> MemTotal:        4143632 kB
> MemFree:         3845248 kB
> MemAvailable:    3947932 kB
> 
> [root@localhost ~]# lsmem
> RANGE                                  SIZE  STATE REMOVABLE BLOCK
> 0x0000000000000000-0x000000000fffffff  256M online        no     0
> 0x0000000010000000-0x000000006fffffff  1.5G online       yes   1-6
> 0x0000000070000000-0x00000000ffffffff  2.3G online        no  7-15
> 
> Memory block size:       256M
> Total online memory:       4G
> Total offline memory:      0B
> 
> I am not sure if we want to have memory hotplug in its current form later
> on (the guest can hotplug memory itself). This is different compared to
> all other architectures. E.g. when booting Fedora 27, it will simply
> hotplug and add all memory. This doesn't make any sense in the context of
> VMs where you want to be able to control from the outside, when and how
> much more memory is given to a VM. But anyhow, seems to work ...

Yes, s390x is different from anyone else in that respect.

I played with it for a bit and it behaves exactly the same under kvm
and under tcg.

> 
> 
> David Hildenbrand (2):
>   s390x/tcg: implement TEST PROTECTION
>   s390x/sclp: fix missing be conversion
> 
>  hw/s390x/sclp.c           |  4 ++--
>  target/s390x/helper.h     |  2 +-
>  target/s390x/mem_helper.c | 41 +++++++++++++++++++++++++++++++++++++++--
>  target/s390x/translate.c  |  2 +-
>  4 files changed, 43 insertions(+), 6 deletions(-)
> 

Thanks, applied.