From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Reply-To: pmorel@linux.ibm.com 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> From: Pierre Morel Date: Mon, 6 May 2019 14:56:12 +0200 MIME-Version: 1.0 In-Reply-To: <20190503134912.39756-8-farman@linux.ibm.com> Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Language: en-US Content-Transfer-Encoding: 8bit Message-Id: <8625f759-0a2d-09af-c8b5-5b312d854ba1@linux.ibm.com> Sender: kvm-owner@vger.kernel.org List-Archive: List-Post: To: Eric Farman , Cornelia Huck , Farhan Ali Cc: Halil Pasic , linux-s390@vger.kernel.org, kvm@vger.kernel.org List-ID: On 03/05/2019 15:49, 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. > > [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; > + > /* 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)) AFAIR, we introduced this code to protect against noop and test with a non zero CDA. This could go away only if there is somewhere the guaranty that noop have always a null CDA (same for test). > 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); > > -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany