From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH 7/7] s390/cio: Remove vfio-ccw checks of command codes References: <20190503134912.39756-1-farman@linux.ibm.com> <20190503134912.39756-8-farman@linux.ibm.com> <20190506173707.40216e76.cohuck@redhat.com> From: Eric Farman Message-ID: <65313674-09be-88c0-4b5e-c99527f26532@linux.ibm.com> Date: Mon, 6 May 2019 11:46:59 -0400 MIME-Version: 1.0 In-Reply-To: <20190506173707.40216e76.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit 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 5/6/19 11:37 AM, Cornelia Huck wrote: > On Fri, 3 May 2019 15:49:12 +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), > > The "Common I/O Device Commands" document actually defines this :) Blech, okay so I didn't look early enough in that document. Section 1.5 it is. :) > >> 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. > > But I agree that everything possible should be sent 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(-) >> >> diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c >> index 36d76b821209..c0a52025bf06 100644 >> --- a/drivers/s390/cio/vfio_ccw_cp.c >> +++ b/drivers/s390/cio/vfio_ccw_cp.c >> @@ -289,8 +289,6 @@ static long copy_ccw_from_iova(struct channel_program *cp, >> #define ccw_is_read_backward(_ccw) (((_ccw)->cmd_code & 0x0F) == 0x0C) >> #define ccw_is_sense(_ccw) (((_ccw)->cmd_code & 0x0F) == CCW_CMD_BASIC_SENSE) >> >> -#define ccw_is_test(_ccw) (((_ccw)->cmd_code & 0x0F) == 0) >> - >> #define ccw_is_noop(_ccw) ((_ccw)->cmd_code == CCW_CMD_NOOP) >> >> #define ccw_is_tic(_ccw) ((_ccw)->cmd_code == CCW_CMD_TIC) >> @@ -314,6 +312,10 @@ static inline int ccw_does_data_transfer(struct ccw1 *ccw) >> if (ccw->count == 0) >> return 0; >> >> + /* If the command is a NOP, then no data will be transferred */ >> + if (ccw_is_noop(ccw)) >> + return 0; >> + > > Don't you need to return 0 here for any test command as well? > > (If I read the doc correctly, we'll just get a unit check in any case, > as there are no parallel I/O interfaces on modern s390 boxes. Even if > we had a parallel I/O interface, we'd just collect the status, and not > get any data transfer. FWIW, the QEMU ccw interpreter for emulated > devices rejects test ccws with a channel program check, which looks > wrong; should be a command reject instead.) I will go back and look. I thought when I sent a test command with an address that wasn't translated I got an unhappy result, which is why I ripped this check out. I was trying to use test CCWs as a safety valve for Halil's Status Modifier concern, so maybe I had something else wrong on that pile. (The careful observer would note that that code was not included here. :) > >> /* If the skip flag is off, then data will be transferred */ >> if (!ccw_is_skip(ccw)) >> return 1; >> @@ -398,7 +400,7 @@ static void ccwchain_cda_free(struct ccwchain *chain, int idx) >> { >> struct ccw1 *ccw = chain->ch_ccw + idx; >> >> - if (ccw_is_test(ccw) || ccw_is_noop(ccw) || ccw_is_tic(ccw)) >> + if (ccw_is_tic(ccw)) >> return; >> >> kfree((void *)(u64)ccw->cda); >> @@ -723,9 +725,6 @@ static int ccwchain_fetch_one(struct ccwchain *chain, >> { >> struct ccw1 *ccw = chain->ch_ccw + idx; >> >> - if (ccw_is_test(ccw) || ccw_is_noop(ccw)) >> - return 0; >> - >> if (ccw_is_tic(ccw)) >> return ccwchain_fetch_tic(chain, idx, cp); >> >