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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> Reviewed-by: Thomas Huth <thuth@redhat.com> Acked-by: Cornelia Huck <cohuck@redhat.com> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com> Message-Id: <20200915194416.107460-7-walling@linux.ibm.com> Signed-off-by: Cornelia Huck <cohuck@redhat.com> |
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| authz | ||
| block | ||
| chardev | ||
| crypto | ||
| disas | ||
| exec | ||
| fpu | ||
| hw | ||
| io | ||
| libdecnumber | ||
| migration | ||
| monitor | ||
| net | ||
| qapi | ||
| qemu | ||
| qom | ||
| scsi | ||
| standard-headers | ||
| sysemu | ||
| tcg | ||
| ui | ||
| user | ||
| elf.h | ||
| glib-compat.h | ||
| qemu-common.h | ||
| qemu-io.h | ||
| trace-tcg.h | ||