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Tue, 15 Sep 2020 14:16:24 +0000 (GMT) Received: from oc4221205838.ibm.com (unknown [9.163.85.51]) by b03ledav002.gho.boulder.ibm.com (Postfix) with ESMTP; Tue, 15 Sep 2020 14:16:24 +0000 (GMT) Subject: Re: [PATCH v2 2/3] s390x/pci: Honor DMA limits set by vfio To: Cornelia Huck References: <1600122570-12941-1-git-send-email-mjrosato@linux.ibm.com> <1600122570-12941-3-git-send-email-mjrosato@linux.ibm.com> <20200915132849.5e166b3e.cohuck@redhat.com> From: Matthew Rosato Message-ID: <2913a3f4-0c4e-14d2-9d8e-fda75e5defb4@linux.ibm.com> Date: Tue, 15 Sep 2020 10:16:23 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200915132849.5e166b3e.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-09-15_08:2020-09-15, 2020-09-15 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 adultscore=0 clxscore=1015 lowpriorityscore=0 phishscore=0 impostorscore=0 mlxscore=0 suspectscore=2 malwarescore=0 bulkscore=0 mlxlogscore=999 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009150114 Received-SPF: pass client-ip=148.163.156.1; envelope-from=mjrosato@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/15 09:39:26 X-ACL-Warn: Detected OS = Linux 3.x [generic] [fuzzy] X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: thuth@redhat.com, pmorel@linux.ibm.com, david@redhat.com, schnelle@linux.ibm.com, qemu-s390x@nongnu.org, qemu-devel@nongnu.org, pasic@linux.ibm.com, borntraeger@de.ibm.com, alex.williamson@redhat.com, rth@twiddle.net Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 9/15/20 7:28 AM, Cornelia Huck wrote: > On Mon, 14 Sep 2020 18:29:29 -0400 > Matthew Rosato wrote: > >> When an s390 guest is using lazy unmapping, it can result in a very >> large number of oustanding DMA requests, far beyond the default >> limit configured for vfio. Let's track DMA usage similar to vfio >> in the host, and trigger the guest to flush their DMA mappings >> before vfio runs out. >> >> Signed-off-by: Matthew Rosato >> --- >> hw/s390x/s390-pci-bus.c | 99 +++++++++++++++++++++++++++++++++++++++++++++--- >> hw/s390x/s390-pci-bus.h | 9 +++++ >> hw/s390x/s390-pci-inst.c | 29 +++++++++++--- >> hw/s390x/s390-pci-inst.h | 3 ++ >> 4 files changed, 129 insertions(+), 11 deletions(-) >> > > (...) > >> @@ -737,6 +742,82 @@ static void s390_pci_iommu_free(S390pciState *s, PCIBus *bus, int32_t devfn) >> object_unref(OBJECT(iommu)); >> } >> >> +static bool s390_sync_dma_avail(int fd, unsigned int *avail) > > Not sure I like the name. It sounds like the function checks whether > "sync dma" is available. Maybe s390_update_dma_avail()? > Sounds fine to me. >> +{ >> + struct vfio_iommu_type1_info *info; >> + uint32_t argsz; >> + bool rval = false; >> + int ret; >> + >> + if (avail == NULL) { >> + return false; >> + } >> + >> + argsz = sizeof(struct vfio_iommu_type1_info); >> + info = g_malloc0(argsz); >> + info->argsz = argsz; >> + /* >> + * If the specified argsz is not large enough to contain all >> + * capabilities it will be updated upon return. In this case >> + * use the updated value to get the entire capability chain. >> + */ >> + ret = ioctl(fd, VFIO_IOMMU_GET_INFO, info); >> + if (argsz != info->argsz) { >> + argsz = info->argsz; >> + info = g_realloc(info, argsz); >> + info->argsz = argsz; >> + ret = ioctl(fd, VFIO_IOMMU_GET_INFO, info); >> + } >> + >> + if (ret) { >> + goto out; >> + } >> + >> + /* If the capability exists, update with the current value */ >> + rval = vfio_get_info_dma_avail(info, avail); > > Adding vfio specific things into the generic s390 pci emulation code > looks a bit ugly... I'd prefer to factor that out into a separate file, > especially if you plan to add more vfio-specific things in the future. > Fair. hw/s390x/s390-pci-vfio.* ? >> + >> +out: >> + g_free(info); >> + return rval; >> +} >> + > > (...) > >> diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c >> index 2f7a7d7..6af9af4 100644 >> --- a/hw/s390x/s390-pci-inst.c >> +++ b/hw/s390x/s390-pci-inst.c >> @@ -32,6 +32,9 @@ >> } \ >> } while (0) >> >> +#define INC_DMA_AVAIL(iommu) if (iommu->dma_limit) iommu->dma_limit->avail++; >> +#define DEC_DMA_AVAIL(iommu) if (iommu->dma_limit) iommu->dma_limit->avail--; > > Hm... maybe lowercase inline functions might be better here? > OK >> + >> static void s390_set_status_code(CPUS390XState *env, >> uint8_t r, uint64_t status_code) >> { > > (...) > >> @@ -620,6 +629,7 @@ int rpcit_service_call(S390CPU *cpu, uint8_t r1, uint8_t r2, uintptr_t ra) >> S390PCIIOMMU *iommu; >> S390IOTLBEntry entry; >> hwaddr start, end; >> + uint32_t dma_avail; >> >> if (env->psw.mask & PSW_MASK_PSTATE) { >> s390_program_interrupt(env, PGM_PRIVILEGED, ra); >> @@ -675,8 +685,9 @@ int rpcit_service_call(S390CPU *cpu, uint8_t r1, uint8_t r2, uintptr_t ra) >> } >> >> start += entry.len; >> - while (entry.iova < start && entry.iova < end) { >> - s390_pci_update_iotlb(iommu, &entry); >> + dma_avail = 1; /* Assume non-zero dma_avail to start */ >> + while (entry.iova < start && entry.iova < end && dma_avail > 0) { >> + dma_avail = s390_pci_update_iotlb(iommu, &entry); >> entry.iova += PAGE_SIZE; >> entry.translated_addr += PAGE_SIZE; >> } >> @@ -689,7 +700,13 @@ err: >> s390_pci_generate_error_event(error, pbdev->fh, pbdev->fid, start, 0); >> } else { >> pbdev->fmb.counter[ZPCI_FMB_CNT_RPCIT]++; >> - setcc(cpu, ZPCI_PCI_LS_OK); >> + if (dma_avail > 0) { > > When I compile this (with a headers update), the compiler moans here > about an uninitialized variable. > D'oh. Obviously dma_avail needs to be initialized outside of the if/else -- I'll double-check the logic here and fix. >> + setcc(cpu, ZPCI_PCI_LS_OK); >> + } else { >> + /* vfio DMA mappings are exhausted, trigger a RPCIT */ >> + setcc(cpu, ZPCI_PCI_LS_ERR); >> + s390_set_status_code(env, r1, ZPCI_RPCIT_ST_INSUFF_RES); >> + } >> } >> return 0; >> } > > (...) >