[Bug 1879646] [NEW] [Feature request] x86: dump MSR features in human form

[Philippe Mathieu-Daudé]

Public bug reported:

QEMU might fail because host/guest cpu features are not properly
configured:

qemu-system-x86_64: error: failed to set MSR 0x48f to 0x7fefff00036dfb
qemu-system-x86_64: /root/qemu-master/target/i386/kvm.c:2695:
kvm_buf_set_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed.

To ease debugging, it the MSR features bit could be dumped.

Example in this thread:

https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg05593.html

  The high 32 bits are 0111 1111 1110 1111 1111 1111.

  The low 32 bits are  0000 0011 0110 1101 1111 1011.

  The features that are set are the xor, so 0111 1100 1000 0010 0000
0100:

  - bit 2, vmx-exit-nosave-debugctl
  - bit 9, host address space size, is handled automatically by QEMU
  - bit 15, vmx-exit-ack-intr
  - bit 17, vmx-exit-save-pat
  - bit 18, vmx-exit-load-pat
  - bit 19, vmx-exit-save-efer
  - bit 20, vmx-exit-load-efer
  - bit 21, vmx-exit-save-preemption-timer

This output ^^^ is easier to digest.

** Affects: qemu
     Importance: Undecided
         Status: New


** Tags: i386

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https://bugs.launchpad.net/bugs/1879646

Title:
  [Feature request] x86: dump MSR features in human form

Status in QEMU:
  New

Bug description:
  QEMU might fail because host/guest cpu features are not properly
  configured:

  qemu-system-x86_64: error: failed to set MSR 0x48f to 0x7fefff00036dfb
  qemu-system-x86_64: /root/qemu-master/target/i386/kvm.c:2695:
  kvm_buf_set_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed.

  To ease debugging, it the MSR features bit could be dumped.

  Example in this thread:

  https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg05593.html

    The high 32 bits are 0111 1111 1110 1111 1111 1111.

    The low 32 bits are  0000 0011 0110 1101 1111 1011.

    The features that are set are the xor, so 0111 1100 1000 0010 0000
  0100:

    - bit 2, vmx-exit-nosave-debugctl
    - bit 9, host address space size, is handled automatically by QEMU
    - bit 15, vmx-exit-ack-intr
    - bit 17, vmx-exit-save-pat
    - bit 18, vmx-exit-load-pat
    - bit 19, vmx-exit-save-efer
    - bit 20, vmx-exit-load-efer
    - bit 21, vmx-exit-save-preemption-timer

  This output ^^^ is easier to digest.

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