| Message ID | 20200624202312.28349-7-walling@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | s390: Extended-Length SCCB & DIAGNOSE 0x318 | expand |
On Wed, 24 Jun 2020 16:23:10 -0400 Collin Walling <walling@linux.ibm.com> wrote: > 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 <walling@linux.ibm.com> > --- > hw/s390x/sclp.c | 24 +++++++++++++++++++++++- > 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, 34 insertions(+), 1 deletion(-) > (...) > @@ -111,6 +131,8 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb) > CPUEntry *entries_start = (void *)sccb + offset_cpu; > > if (!sccb_verify_length(sccb, machine->possible_cpus->len, offset_cpu)) { > + qemu_log_mask(LOG_GUEST_ERROR, "insufficient sccb size to store " > + "read scp info response\n"); Not sure if logging needed/provided length would be helpful here. > return; > } > (...) Acked-by: Cornelia Huck <cohuck@redhat.com>
On 6/26/20 6:01 AM, Cornelia Huck wrote: > On Wed, 24 Jun 2020 16:23:10 -0400 > Collin Walling <walling@linux.ibm.com> wrote: > >> 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 <walling@linux.ibm.com> >> --- >> hw/s390x/sclp.c | 24 +++++++++++++++++++++++- >> 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, 34 insertions(+), 1 deletion(-) >> > > (...) > >> @@ -111,6 +131,8 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb) >> CPUEntry *entries_start = (void *)sccb + offset_cpu; >> >> if (!sccb_verify_length(sccb, machine->possible_cpus->len, offset_cpu)) { >> + qemu_log_mask(LOG_GUEST_ERROR, "insufficient sccb size to store " >> + "read scp info response\n"); > > Not sure if logging needed/provided length would be helpful here. > I had the thought that it may be beneficial for kernel development -- it gives a response if an SCCB size needs to be larger. >> return; >> } >> > > (...) > > Acked-by: Cornelia Huck <cohuck@redhat.com> > Thanks.
On Wed, 15 Jul 2020 11:35:06 -0400 Collin Walling <walling@linux.ibm.com> wrote: > On 6/26/20 6:01 AM, Cornelia Huck wrote: > > On Wed, 24 Jun 2020 16:23:10 -0400 > > Collin Walling <walling@linux.ibm.com> wrote: > > > >> 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 <walling@linux.ibm.com> > >> --- > >> hw/s390x/sclp.c | 24 +++++++++++++++++++++++- > >> 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, 34 insertions(+), 1 deletion(-) > >> > > > > (...) > > > >> @@ -111,6 +131,8 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb) > >> CPUEntry *entries_start = (void *)sccb + offset_cpu; > >> > >> if (!sccb_verify_length(sccb, machine->possible_cpus->len, offset_cpu)) { > >> + qemu_log_mask(LOG_GUEST_ERROR, "insufficient sccb size to store " > >> + "read scp info response\n"); > > > > Not sure if logging needed/provided length would be helpful here. > > > > I had the thought that it may be beneficial for kernel development -- it > gives a response if an SCCB size needs to be larger. If we have the info, we might as well log it, I guess.
diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c index 518f630938..2e83b4f598 100644 --- a/hw/s390x/sclp.c +++ b/hw/s390x/sclp.c @@ -22,6 +22,7 @@ #include "hw/s390x/event-facility.h" #include "hw/s390x/s390-pci-bus.h" #include "hw/s390x/ipl.h" +#include "qemu/log.h" static inline SCLPDevice *get_sclp_device(void) { @@ -56,6 +57,19 @@ static bool sccb_verify_boundary(uint64_t sccb_addr, uint32_t code, uint64_t sccb_boundary = (sccb_addr & PAGE_MASK) + PAGE_SIZE; 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; @@ -72,6 +86,10 @@ static bool sccb_verify_length(SCCB *sccb, int num_cpus, int offset_cpu) if (be16_to_cpu(sccb->h.length) < required_len) { sccb->h.response_code = cpu_to_be16(SCLP_RC_INSUFFICIENT_SCCB_LENGTH); + if (s390_has_feat(S390_FEAT_EXTENDED_LENGTH_SCCB) && + sccb->h.control_mask[2] & SCLP_VARIABLE_LENGTH_RESPONSE) { + sccb->h.length = required_len; + } return false; } return true; @@ -96,7 +114,9 @@ static void prepare_cpu_entries(MachineState *ms, CPUEntry *entry, int *count) static inline int get_read_scp_info_offset_cpu(void) { - return offsetof(ReadInfo, entries); + return s390_has_feat(S390_FEAT_EXTENDED_LENGTH_SCCB) ? + offsetof(ReadInfo, entries) : + SCLP_READ_SCP_INFO_FIXED_CPU_OFFSET; } /* Provide information about the configuration, CPUs and storage */ @@ -111,6 +131,8 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb) CPUEntry *entries_start = (void *)sccb + offset_cpu; if (!sccb_verify_length(sccb, machine->possible_cpus->len, offset_cpu)) { + qemu_log_mask(LOG_GUEST_ERROR, "insufficient sccb size to store " + "read scp info response\n"); return; } diff --git a/include/hw/s390x/sclp.h b/include/hw/s390x/sclp.h index 822eff4396..ef2d63eae9 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 5942f81f16..1c04cc18f4 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 8ddeebc544..6857f657fb 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 f2f75d2a57..a2d5ad78f6 100644 --- a/target/s390x/kvm.c +++ b/target/s390x/kvm.c @@ -2456,6 +2456,14 @@ 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);
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 <walling@linux.ibm.com> --- hw/s390x/sclp.c | 24 +++++++++++++++++++++++- 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, 34 insertions(+), 1 deletion(-)