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Thu, 16 Dec 2021 14:51:23 +0000 (GMT) Received: from [9.211.79.24] (unknown [9.211.79.24]) by b03ledav004.gho.boulder.ibm.com (Postfix) with ESMTP; Thu, 16 Dec 2021 14:51:23 +0000 (GMT) Message-ID: Date: Thu, 16 Dec 2021 09:51:22 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.0 Subject: Re: [PATCH 23/32] KVM: s390: pci: handle refresh of PCI translations Content-Language: en-US To: Niklas Schnelle , Pierre Morel , linux-s390@vger.kernel.org Cc: alex.williamson@redhat.com, cohuck@redhat.com, farman@linux.ibm.com, borntraeger@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, gerald.schaefer@linux.ibm.com, agordeev@linux.ibm.com, frankja@linux.ibm.com, david@redhat.com, imbrenda@linux.ibm.com, vneethv@linux.ibm.com, oberpar@linux.ibm.com, freude@linux.ibm.com, thuth@redhat.com, pasic@linux.ibm.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20211207205743.150299-1-mjrosato@linux.ibm.com> <20211207205743.150299-24-mjrosato@linux.ibm.com> <9a953a7938218afed246e93995d22ee7d09a81f3.camel@linux.ibm.com> From: Matthew Rosato In-Reply-To: <9a953a7938218afed246e93995d22ee7d09a81f3.camel@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: aUNvU2mYj5-qgHi9vbqg7vbk8wcH4f7K X-Proofpoint-GUID: i_4QVHy6VyEac7L87FLOjuI9Dotnqax_ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2021-12-16_05,2021-12-16_01,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 mlxlogscore=999 lowpriorityscore=0 priorityscore=1501 impostorscore=0 suspectscore=0 clxscore=1015 malwarescore=0 spamscore=0 mlxscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2110150000 definitions=main-2112160081 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/16/21 9:39 AM, Niklas Schnelle wrote: > On Tue, 2021-12-14 at 12:54 -0500, Matthew Rosato wrote: >> On 12/14/21 11:59 AM, Pierre Morel wrote: >>> >>> On 12/7/21 21:57, Matthew Rosato wrote: >>>> Add a routine that will perform a shadow operation between a guest >>>> and host IOAT. A subsequent patch will invoke this in response to >>>> an 04 RPCIT instruction intercept. >>>> >>>> Signed-off-by: Matthew Rosato >>>> --- >>>> arch/s390/include/asm/kvm_pci.h | 1 + >>>> arch/s390/include/asm/pci_dma.h | 1 + >>>> arch/s390/kvm/pci.c | 191 ++++++++++++++++++++++++++++++++ >>>> arch/s390/kvm/pci.h | 4 +- >>>> 4 files changed, 196 insertions(+), 1 deletion(-) >>>> > ---8<--- >>> >>>> + >>>> +int kvm_s390_pci_refresh_trans(struct kvm_vcpu *vcpu, unsigned long req, >>>> + unsigned long start, unsigned long size) >>>> +{ >>>> + struct zpci_dev *zdev; >>>> + u32 fh; >>>> + int rc; >>>> + >>>> + /* If the device has a SHM bit on, let userspace take care of >>>> this */ >>>> + fh = req >> 32; >>>> + if ((fh & aift.mdd) != 0) >>>> + return -EOPNOTSUPP; >>> >>> I think you should make this check in the caller. >> >> OK >> >>>> + >>>> + /* Make sure this is a valid device associated with this guest */ >>>> + zdev = get_zdev_by_fh(fh); >>>> + if (!zdev || !zdev->kzdev || zdev->kzdev->kvm != vcpu->kvm) >>>> + return -EINVAL; >>>> + >>>> + /* Only proceed if the device is using the assist */ >>>> + if (zdev->kzdev->ioat.head[0] == 0) >>>> + return -EOPNOTSUPP; >>> >>> Using the assist means using interpretation over using interception and >>> legacy vfio-pci. right? >> >> Right - more specifically that the IOAT assist feature was never set via >> the vfio feature ioctl, so we can't handle the RPCIT for this device and >> so throw to userspace. >> >> The way the QEMU series is being implemented, a device using >> interpretation will always have the IOAT feature set on. >> >>>> + >>>> + rc = dma_table_shadow(vcpu, zdev, start, size); >>>> + if (rc > 0) >>>> + rc = zpci_refresh_trans((u64) zdev->fh << 32, start, size); >>> >>> Here you lose the status reported by the hardware. >>> You should directly use __rpcit(fn, addr, range, &status); >> >> OK, I can have a look at doing this. >> >> @Niklas thoughts on how you would want this exported. Renamed to >> zpci_rpcit or so? > > Hmm with using __rpcit() directly we would lose the error reporting in > s390dbf and this ist still kind of a RPCIT in the host. How about we > add the status as an out parameter to zpci_refresh_trans()? But yes if Another advantage of doing this would be that we then also keep the cc2 retry logic in zpci_refresh_trans(), which would be nice. However we do still lose the returned CC value from the instruction. But I think we can infer a CC1 from a nonzero status and a CC3 from a zero status so maybe this is OK too. I think I will add the status parm to zpci_refresh_trans(). FWIW, I do also think it is likely we will end up with a s390dbf for kvm-pci at some point after this initial series. > you prefer to use __rpcit() directly I would rename it to zpci_rpcit(). > >> > > ---8<--- >