Re: [qemu-s390x] [PATCH v2 1/3] s390x/sclp: proper support of larger send and receive masks

[Claudio Imbrenda]

On Fri, 23 Feb 2018 11:31:46 +0100
Cornelia Huck <address@hidden> wrote:

> On Thu, 22 Feb 2018 17:22:57 +0100
> Claudio Imbrenda <address@hidden> wrote:
> 
> > Until 67915de9f0383ccf4a ("s390x/event-facility: variable-length
> > event masks") we only supported sclp event masks of size exactly 4
> > bytes, even though  
> 
> s/of size/of a size of/

will fix

> > the archiecture allows the guests to set up sclp event masks from 1
> > to  
> 
> s/archiecture/architecture/

will fix

> > 1021 bytes in length.
> > After that patch, the behaviour was almost compliant, but some
> > issues were still remaining, in particular regarding the handling
> > of selective reads and migration.
> > 
> > When setting the sclp event mask, a mask size is also specified.
> > Until now we only considered the size in order to decide which bits
> > to save in the internal state. On the other hand, when a guest
> > performs a selective read, it sends a mask, but it does not specify
> > a size; the implied size is the size of the last mask that has been
> > set.
> > 
> > Specifying bits in the mask of selective read that are not
> > available in the internal mask should return an error, and bits
> > past the end of the mask should obviously be ignored. This can only
> > be achieved by keeping track of the lenght of the mask.
> > 
> > The mask length is thus now part of the internal state that needs
> > to be migrated.
> > 
> > This patch fixes the handling of selective reads, whose size will
> > now match the length of the event mask, as per architecture.
> > 
> > While the default behaviour is to be compliant with the
> > architecture, when using older machine models the old broken
> > behaviour is selected (allowing only masks of size exactly 4), in
> > order to be able to migrate toward older versions.
> > 
> > Fixes: 67915de9f0383ccf4a ("s390x/event-facility: variable-length
> > event masks") Signed-off-by: Claudio Imbrenda
> > <address@hidden> ---
> >  hw/s390x/event-facility.c  | 91
> > +++++++++++++++++++++++++++++++++++++++-------
> > hw/s390x/s390-virtio-ccw.c |  8 +++- 2 files changed, 85
> > insertions(+), 14 deletions(-)  
> 
> Looks reasonable.
>