From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH v2 7/7] s390/cio: Remove vfio-ccw checks of command codes References: <20190514234248.36203-1-farman@linux.ibm.com> <20190514234248.36203-8-farman@linux.ibm.com> <20190515144305.46a2ecb1.cohuck@redhat.com> From: Eric Farman Date: Wed, 15 May 2019 09:36:01 -0400 MIME-Version: 1.0 In-Reply-To: <20190515144305.46a2ecb1.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Message-Id: <1f0e2084-2e3d-bc97-f8cf-a40f194d7288@linux.ibm.com> Sender: kvm-owner@vger.kernel.org List-Archive: List-Post: To: Cornelia Huck Cc: Farhan Ali , Halil Pasic , Pierre Morel , linux-s390@vger.kernel.org, kvm@vger.kernel.org List-ID: On 5/15/19 8:43 AM, Cornelia Huck wrote: > On Wed, 15 May 2019 01:42:48 +0200 > Eric Farman wrote: > >> If the CCW being processed is a No-Operation, then by definition no >> data is being transferred. Let's fold those checks into the normal >> CCW processors, rather than skipping out early. >> >> Likewise, if the CCW being processed is a "test" (an invented >> definition to simply mean it ends in a zero), let's permit that to go >> through to the hardware. There's nothing inherently unique about >> those command codes versus one that ends in an eight [1], or any other >> otherwise valid command codes that are undefined for the device type >> in question. > > Hm... let's tweak that a bit? It's not that "test" is an invented > category; it's just that this has not been a valid command for > post-s/370 and therefore should not get any special treatment and just > be sent to the hardware? Agreed, I should've re-read that one before I sent it... How about: Likewise, if the CCW being processed is a "test" (a category defined here as an opcode that contains zero in the lowest four bits) then no special processing is necessary as far as vfio-ccw is concerned. These command codes have not been valid since the S/370 days, meaning they are invalid in the same way as one that ends in an eight [1] or an otherwise valid command code that is undefined for the device type in question. Considering that, let's just process "test" CCWs like any other CCW, and send everything to the hardware. > >> >> [1] POPS states that a x08 is a TIC CCW, and that having any high-order >> bits enabled is invalid for format-1 CCWs. For format-0 CCWs, the >> high-order bits are ignored. >> >> Signed-off-by: Eric Farman >> --- >> drivers/s390/cio/vfio_ccw_cp.c | 11 +++++------ >> 1 file changed, 5 insertions(+), 6 deletions(-) >