Re: [PATCH 1/2] pc-bios: s390x: Ensure Read IPL memory is clean

[Cornelia Huck]

On Thu, 19 Nov 2020 17:57:28 +0100
Eric Farman <farman@linux.ibm.com> wrote:

> If, for example, we boot off a virtio device and chreipl to a vfio-ccw
> device, the space at lowcore will be non-zero. We build a Read IPL CCW
> at address zero, but it will have leftover PSW data that will conflict
> with the Format-0 CCW being generated:
> 
> 0x0: 00080000 80010000
>        ------ Ccw0.cda
>               -- Ccw0.chainData
>                 -- Reserved bits
> 
> The data address will be overwritten with the correct value (0x0), but
> the apparent data chain bit will cause subsequent memory to be used as
> the target of the data store, which may not be where we expect (0x0).
> 
> Clear out this space when we boot from DASD, so that we know it exists
> exactly as we expect.
> 
> Signed-off-by: Eric Farman <farman@linux.ibm.com>
> Reviewed-by: Jason J. Herne <jjherne@linux.ibm.com>
> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
>  pc-bios/s390-ccw/dasd-ipl.c | 3 +++
>  1 file changed, 3 insertions(+)

Acked-by: Cornelia Huck <cohuck@redhat.com>