From d7ebb3044bd446baad16ce0e812736e4960f9d5e Mon Sep 17 00:00:00 2001 From: Collin Walling Date: Tue, 15 Sep 2020 15:44:14 -0400 Subject: [PATCH 6/8] s390/sclp: add extended-length sccb support for kvm guest As more features and facilities are added to the Read SCP Info (RSCPI) response, more space is required to store them. The space used to store these new features intrudes on the space originally used to store CPU entries. This means as more features and facilities are added to the RSCPI response, less space can be used to store CPU entries. With the Extended-Length SCCB (ELS) facility, a KVM guest can execute the RSCPI command and determine if the SCCB is large enough to store a complete reponse. If it is not large enough, then the required length will be set in the SCCB header. The caller of the SCLP command is responsible for creating a large-enough SCCB to store a complete response. Proper checking should be in place, and the caller should execute the command once-more with the large-enough SCCB. This facility also enables an extended SCCB for the Read CPU Info (RCPUI) command. When this facility is enabled, the boundary violation response cannot be a result from the RSCPI, RSCPI Forced, or RCPUI commands. In order to tolerate kernels that do not yet have full support for this feature, a "fixed" offset to the start of the CPU Entries within the Read SCP Info struct is set to allow for the original 248 max entries when this feature is disabled. Additionally, this is introduced as a CPU feature to protect the guest from migrating to a machine that does not support storing an extended SCCB. This could otherwise hinder the VM from being able to read all available CPU entries after migration (such as during re-ipl). Signed-off-by: Collin Walling Reviewed-by: Thomas Huth Acked-by: Cornelia Huck Reviewed-by: Claudio Imbrenda Message-Id: <20200915194416.107460-7-walling@linux.ibm.com> Signed-off-by: Cornelia Huck (backported from commit: 1ecd6078f587cfadda8edc93d45b5072e35f2d17) Signed-off-by: Collin Walling --- hw/s390x/sclp.c | 41 +++++++++++++++++++++++++---- include/hw/s390x/sclp.h | 1 + target/s390x/cpu_features_def.inc.h | 1 + target/s390x/gen-features.c | 1 + target/s390x/kvm.c | 8 ++++++ 5 files changed, 47 insertions(+), 5 deletions(-) diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c index 22e5f4c75e..d2fd37c9c5 100644 --- a/hw/s390x/sclp.c +++ b/hw/s390x/sclp.c @@ -33,13 +33,30 @@ static inline SCLPDevice *get_sclp_device(void) return sclp; } -static bool sccb_verify_boundary(uint64_t sccb_addr, uint16_t sccb_len) +static bool sccb_verify_boundary(uint64_t sccb_addr, uint16_t sccb_len, + uint32_t code) { uint64_t sccb_max_addr = sccb_addr + sccb_len - 1; uint64_t sccb_boundary = (sccb_addr & PAGE_MASK) + PAGE_SIZE; - if (sccb_max_addr < sccb_boundary) { - return true; + switch (code & SCLP_CMD_CODE_MASK) { + case SCLP_CMDW_READ_SCP_INFO: + case SCLP_CMDW_READ_SCP_INFO_FORCED: + case SCLP_CMDW_READ_CPU_INFO: + /* + * An extended-length SCCB is only allowed for Read SCP/CPU Info and + * is allowed to exceed the 4k boundary. The respective commands will + * set the length field to the required length if an insufficient + * SCCB length is provided. + */ + if (s390_has_feat(S390_FEAT_EXTENDED_LENGTH_SCCB)) { + return true; + } + /* fallthrough */ + default: + if (sccb_max_addr < sccb_boundary) { + return true; + } } return false; @@ -64,6 +81,12 @@ static void prepare_cpu_entries(MachineState *ms, CPUEntry *entry, int *count) #define SCCB_REQ_LEN(s, max_cpus) (sizeof(s) + max_cpus * sizeof(CPUEntry)) +static inline bool ext_len_sccb_supported(SCCBHeader header) +{ + return s390_has_feat(S390_FEAT_EXTENDED_LENGTH_SCCB) && + header.control_mask[2] & SCLP_VARIABLE_LENGTH_RESPONSE; +} + /* Provide information about the configuration, CPUs and storage */ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb) { @@ -73,10 +96,15 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb) int rnsize, rnmax; IplParameterBlock *ipib = s390_ipl_get_iplb(); int required_len = SCCB_REQ_LEN(ReadInfo, machine->possible_cpus->len); - int offset_cpu = offsetof(ReadInfo, entries); + int offset_cpu = s390_has_feat(S390_FEAT_EXTENDED_LENGTH_SCCB) ? + offsetof(ReadInfo, entries) : + SCLP_READ_SCP_INFO_FIXED_CPU_OFFSET; CPUEntry *entries_start = (void *)sccb + offset_cpu; if (be16_to_cpu(sccb->h.length) < required_len) { + if (ext_len_sccb_supported(sccb->h)) { + sccb->h.length = cpu_to_be16(required_len); + } sccb->h.response_code = cpu_to_be16(SCLP_RC_INSUFFICIENT_SCCB_LENGTH); return; } @@ -137,6 +165,9 @@ static void sclp_read_cpu_info(SCLPDevice *sclp, SCCB *sccb) int required_len = SCCB_REQ_LEN(ReadCpuInfo, machine->possible_cpus->len); if (be16_to_cpu(sccb->h.length) < required_len) { + if (ext_len_sccb_supported(sccb->h)) { + sccb->h.length = cpu_to_be16(required_len); + } sccb->h.response_code = cpu_to_be16(SCLP_RC_INSUFFICIENT_SCCB_LENGTH); return; } @@ -269,7 +300,7 @@ int sclp_service_call(CPUS390XState *env, uint64_t sccb, uint32_t code) goto out_write; } - if (!sccb_verify_boundary(sccb, be16_to_cpu(work_sccb->h.length))) { + if (!sccb_verify_boundary(sccb, be16_to_cpu(work_sccb->h.length), code)) { work_sccb->h.response_code = cpu_to_be16(SCLP_RC_SCCB_BOUNDARY_VIOLATION); goto out_write; } diff --git a/include/hw/s390x/sclp.h b/include/hw/s390x/sclp.h index f0836d61ae..e2b95a7590 100644 --- a/include/hw/s390x/sclp.h +++ b/include/hw/s390x/sclp.h @@ -110,6 +110,7 @@ typedef struct CPUEntry { uint8_t reserved1; } QEMU_PACKED CPUEntry; +#define SCLP_READ_SCP_INFO_FIXED_CPU_OFFSET 128 typedef struct ReadInfo { SCCBHeader h; uint16_t rnmax; diff --git a/target/s390x/cpu_features_def.inc.h b/target/s390x/cpu_features_def.inc.h index 31dff0d84e..7594f7a7ef 100644 --- a/target/s390x/cpu_features_def.inc.h +++ b/target/s390x/cpu_features_def.inc.h @@ -97,6 +97,7 @@ DEF_FEAT(GUARDED_STORAGE, "gs", STFL, 133, "Guarded-storage facility") DEF_FEAT(VECTOR_PACKED_DECIMAL, "vxpd", STFL, 134, "Vector packed decimal facility") DEF_FEAT(VECTOR_ENH, "vxeh", STFL, 135, "Vector enhancements facility") DEF_FEAT(MULTIPLE_EPOCH, "mepoch", STFL, 139, "Multiple-epoch facility") +DEF_FEAT(EXTENDED_LENGTH_SCCB, "els", STFL, 140, "Extended-length SCCB facility") DEF_FEAT(TEST_PENDING_EXT_INTERRUPTION, "tpei", STFL, 144, "Test-pending-external-interruption facility") DEF_FEAT(INSERT_REFERENCE_BITS_MULT, "irbm", STFL, 145, "Insert-reference-bits-multiple facility") DEF_FEAT(MSA_EXT_8, "msa8-base", STFL, 146, "Message-security-assist-extension-8 facility (excluding subfunctions)") diff --git a/target/s390x/gen-features.c b/target/s390x/gen-features.c index 6278845b12..3e2429f702 100644 --- a/target/s390x/gen-features.c +++ b/target/s390x/gen-features.c @@ -522,6 +522,7 @@ static uint16_t full_GEN12_GA1[] = { S390_FEAT_AP_QUEUE_INTERRUPT_CONTROL, S390_FEAT_AP_FACILITIES_TEST, S390_FEAT_AP, + S390_FEAT_EXTENDED_LENGTH_SCCB, }; static uint16_t full_GEN12_GA2[] = { diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c index 0c9d14b4b1..eb6a6c5cd1 100644 --- a/target/s390x/kvm.c +++ b/target/s390x/kvm.c @@ -2349,6 +2349,14 @@ void kvm_s390_get_host_cpu_model(S390CPUModel *model, Error **errp) KVM_S390_VM_CRYPTO_ENABLE_APIE)) { set_bit(S390_FEAT_AP, model->features); } + + /* + * Extended-Length SCCB is handled entirely within QEMU. + * For PV guests this is completely fenced by the Ultravisor, as Service + * Call error checking and STFLE interpretation are handled via SIE. + */ + set_bit(S390_FEAT_EXTENDED_LENGTH_SCCB, model->features); + /* strip of features that are not part of the maximum model */ bitmap_and(model->features, model->features, model->def->full_feat, S390_FEAT_MAX); -- 2.25.1