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Date: Mon, 30 Jul 2018 17:47:14 +0200
From: Cornelia Huck <cohuck@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/1] s390x/sclp: fix maxram calculation
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To: David Hildenbrand <david@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>, qemu-devel <qemu-devel@nongnu.org>, qemu-s390x <qemu-s390x@nongnu.org>, Alexander Graf <agraf@suse.de>, Thomas Huth <thuth@redhat.com>, Richard Henderson <rth@twiddle.net>, Janosch Frank <frankja@linux.vnet.ibm.com>, Halil Pasic <pasic@linux.vnet.ibm.com>, imbrenda@linux.vnet.ibm.com

On Mon, 30 Jul 2018 17:43:42 +0200
David Hildenbrand <david@redhat.com> wrote:

> On 30.07.2018 16:09, Christian Borntraeger wrote:
> > We clamp down ram_size to match the sclp increment size. We do
> > not do the same for maxram_size, which means for large guests
> > with some sizes (e.g. -m 50000) maxram_size differs from ram_size.
> > This can break other code (e.g. CMMA migration) which uses maxram_size
> > to calculate the number of pages and then throws some errors.
> > 
> > Fixes: 82fab5c5b90e468f3e9d54c ("s390x/sclp: remove memory hotplug support")
> > Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> > CC: qemu-stable@nongnu.org
> > CC: David Hildenbrand <david@redhat.com>
> > ---
> >  hw/s390x/sclp.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c
> > index bd2a024..4510a80 100644
> > --- a/hw/s390x/sclp.c
> > +++ b/hw/s390x/sclp.c
> > @@ -320,6 +320,7 @@ static void sclp_memory_init(SCLPDevice *sclp)
> >      initial_mem = initial_mem >> increment_size << increment_size;
> >  
> >      machine->ram_size = initial_mem;
> > +    machine->maxram_size = initial_mem;
> >      /* let's propagate the changed ram size into the global variable. */
> >      ram_size = initial_mem;
> >  }
> >   
> 
> BTW, I handle it in may private patch like this
> 
>  static inline SCLPDevice *get_sclp_device(void)
>  {
> @@ -319,9 +321,12 @@ static void sclp_memory_init(SCLPDevice *sclp)
>       * down to align with the nearest increment boundary. */
>      initial_mem = initial_mem >> increment_size << increment_size;
> 
> -    machine->ram_size = initial_mem;
> -    /* let's propagate the changed ram size into the global variable. */
> -    ram_size = initial_mem;
> +    /* propagate the changed ram size into the different places */
> +    if (initial_mem != machine->ram_size) {
> +        machine->maxram_size -= machine->ram_size - initial_mem;
> +        machine->ram_size = initial_mem;
> +        ram_size = initial_mem;
> +    }
>  }
> 
> You would right now overwrite any maxmem setting (which might be ok as
> we don't support it yet).
> 

So, will you (for whatever value of 'you') submit more patches for 3.1?