From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH v2 1/7] s390/cio: Update SCSW if it points to the end of the chain References: <20190514234248.36203-1-farman@linux.ibm.com> <20190514234248.36203-2-farman@linux.ibm.com> From: Farhan Ali Date: Wed, 15 May 2019 10:30:35 -0400 MIME-Version: 1.0 In-Reply-To: <20190514234248.36203-2-farman@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Message-Id: <978ed329-cc81-b08f-8d59-ae92350abc17@linux.ibm.com> Sender: kvm-owner@vger.kernel.org List-Archive: List-Post: To: Eric Farman , Cornelia Huck Cc: Halil Pasic , Pierre Morel , linux-s390@vger.kernel.org, kvm@vger.kernel.org List-ID: On 05/14/2019 07:42 PM, Eric Farman wrote: > Per the POPs [1], when processing an interrupt the SCSW.CPA field of an > IRB generally points to 8 bytes after the last CCW that was executed > (there are exceptions, but this is the most common behavior). > > In the case of an error, this points us to the first un-executed CCW > in the chain. But in the case of normal I/O, the address points beyond > the end of the chain. While the guest generally only cares about this > when possibly restarting a channel program after error recovery, we > should convert the address even in the good scenario so that we provide > a consistent, valid, response upon I/O completion. > > [1] Figure 16-6 in SA22-7832-11. The footnotes in that table also state > that this is true even if the resulting address is invalid or protected, > but moving to the end of the guest chain should not be a surprise. > > Signed-off-by: Eric Farman > --- > drivers/s390/cio/vfio_ccw_cp.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c > index 384b3987eeb4..41f48b8790bc 100644 > --- a/drivers/s390/cio/vfio_ccw_cp.c > +++ b/drivers/s390/cio/vfio_ccw_cp.c > @@ -870,7 +870,11 @@ void cp_update_scsw(struct channel_program *cp, union scsw *scsw) > */ > list_for_each_entry(chain, &cp->ccwchain_list, next) { > ccw_head = (u32)(u64)chain->ch_ccw; > - if (is_cpa_within_range(cpa, ccw_head, chain->ch_len)) { > + /* > + * On successful execution, cpa points just beyond the end > + * of the chain. > + */ > + if (is_cpa_within_range(cpa, ccw_head, chain->ch_len + 1)) { > /* > * (cpa - ccw_head) is the offset value of the host > * physical ccw to its chain head. > Reviewed-by: Farhan Ali