Re: [PATCH v3 12/12] KVM: s390: allow to change the IAM clear strategy dynamically

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On 29.11.18 13:38, Cornelia Huck wrote:
On Wed, 28 Nov 2018 11:19:43 +0100
Michael Mueller <mimu@xxxxxxxxxxxxx> wrote:

The sysctl file /proc/sys/s390/iam_clear_strategy defines under which
condition the GISA IAM is cleared before entering the SIE in routine
vcpu_pre_run().

The following IAM clear strategies are available:

   0 : the mask is never cleared
   1 : the mask is cleared if I/O interruptions are not
       disabled by the PSW of the vcpu entering the SIE
   2 : the mask is unconditionally cleared

The default IAM clear strategy after system boot is 0.

Set the new strategy by means of the sysctl command or write to the file.

   sysctl s390.iam_clear_strategy=1
   echo 2 >/proc/sys/s390/iam_clear_strategy

This wants some documentation, I think. How is the admin supposed to
know which strategy to choose?

The patch will be dropped. The strategy will not be changeable by
an admin. The IAM will never be cleared by the host program during
normal operation except for the GISA clear and GISA drop cases.



Signed-off-by: Michael Mueller <mimu@xxxxxxxxxxxxx>
---
  arch/s390/kvm/interrupt.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++
  arch/s390/kvm/kvm-s390.c  |  1 +
  arch/s390/kvm/kvm-s390.h  |  1 +
  3 files changed, 71 insertions(+)


--
Mit freundlichen Grüßen / Kind regards
Michael Müller

IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Martina Köderitz
Geschäftsführung: Dirk Wittkopp
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