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[PATCH v6 0/8] s390: Extended-Length SCCB & DIAGNOSE 0x318

From: Collin Walling
Subject: [PATCH v6 0/8] s390: Extended-Length SCCB & DIAGNOSE 0x318
Date: Tue, 15 Sep 2020 15:44:08 -0400



    • sccb_verify_boundary function:
        • s/len/sccb_len
        • removed the endian check/conversion of the sccb_len from within 
          this function (caller is now responsible)

    • proper endian conversion when using header length to malloc

    • use g_autofree for work_sccb

    • added r-b's and acks (thanks!)

    • added a feature-check fence within the diag_318_handler to ensure
        the handler does not complete without proper feature support
        • will throw a program exception if handler is invoked but
          feature is not enabled


    v5 (comment below pertains to version 5)

    Janosch, Thomas, Conny: I've removed your r-b's from patch #3 since I
    added some g_mallocs in place and I'd like to make sure things are
    done properly there (explained in changelog, but let me know if further
    explanation is necessary).

    Janosch, please let me know if the changes to #3 are safe under PV.


    • removed sccb_verify_length function
        - will simply use the length check code that was in place before

    • introduced a macro for calculating required SCCB length
        - takes a struct and max # of cpus as args

    • work_sccb size is now dynamically allocated based on the length
      provided by the guest kernel, instead of always using a static
      4K size
        - as such, the SCCB will have to be read twice:
            - first time to retrieve the header
            - second time with proper size after space for work_sccb 
              is allocated

    • added r-b's and ack's (thanks, everyone!)

    • renamed boundary and length function

    • updated header sync to reflect a change discussed in the respective
        KVM patches

    • s/data_len/offset_cpu

    • added /* fallthrough */ comment in boundary check


    • Device IOCTLs removed
        - diag 318 info is now communicated via sync_regs

    • Reset code removed
        - this is now handled in KVM
        - diag318_info is stored within the CPU reset portion of the

    • Various cleanups for ELS preliminary patches


    • QEMU now handles the instruction call
        - as such, the "enable diag 318" IOCTL has been removed

    • patch #1 now changes the read scp/cpu info functions to
      retrieve the machine state once
        - as such, I have not added any ack's or r-bs since this
          patch differs from the previous version

    • patch #3 introduces a new "get_read_scp_info_data_len"
      function in order clean-up the variable data length assignment
      in patch #7
        - a comment above this function should help clarify what's
          going on to make things a bit easier to read

    • other misc clean ups and fixes
        - s/diag318/diag_318 in order to keep the naming scheme
          consistent with Linux and other diag-related code
        - s/byte_134/fac134 to align naming scheme with Linux


This patch series introduces two features for an s390 KVM quest:
    - Extended-Length SCCB (els) for the Read SCP/CPU Info SCLP 
    - DIAGNOSE 0x318 (diag_318) enabling / migration handling

The diag 318 feature depends on els and KVM support.

The els feature is handled entirely with QEMU, and does not require 
KVM support.

Both features are made available starting with the zEC12-full model.

These patches are introduced together for two main reasons:
    - els allows diag 318 to exist while retaining the original 248 
        VCPU max
    - diag 318 is presented to show how els is useful

Full els support is dependant on the Linux kernel, which must react
to the SCLP response code and set an appropriate-length SCCB. 

A user should take care when tuning the CPU model for a VM.
If a user defines a VM with els support and specifies 248 CPUs, but
the guest Linux kernel cannot react to the SCLP response code, then
the guest will crash immediately upon kernel startup.

Collin L. Walling (8):
  s390/sclp: get machine once during read scp/cpu info
  s390/sclp: rework sclp boundary checks
  s390/sclp: read sccb from mem based on provided length
  s390/sclp: check sccb len before filling in data
  s390/sclp: use cpu offset to locate cpu entries
  s390/sclp: add extended-length sccb support for kvm guest
  s390/kvm: header sync for diag318
  s390: guest support for diagnose 0x318

 hw/s390x/event-facility.c           |   2 +-
 hw/s390x/sclp.c                     | 142 ++++++++++++++++++++--------
 include/hw/s390x/sclp.h             |  11 ++-
 linux-headers/asm-s390/kvm.h        |   7 +-
 linux-headers/linux/kvm.h           |   1 +
 target/s390x/cpu.h                  |   2 +
 target/s390x/cpu_features.h         |   1 +
 target/s390x/cpu_features_def.h.inc |   4 +
 target/s390x/cpu_models.c           |   1 +
 target/s390x/gen-features.c         |   2 +
 target/s390x/kvm.c                  |  47 +++++++++
 target/s390x/machine.c              |  17 ++++
 12 files changed, 194 insertions(+), 43 deletions(-)


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