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Description: KVM: PV: ext call delivered twice when receiver in PSW wait
Symptom: In a secure execution guest, the external interrupt for the
SIGP external call order is delivered twice to a VCPU even
though it was only sent once.
Problem: Under PV, external call interrupts are delivered by the SIGP
interpretation facility, without KVM's involvement. But, if the
receiving CPU is in enabled wait, KVM needs to wake the
receiving CPU such that the interrupt can be delivered. Hence,
in this case, the SIGP external call order causes an
interception. In response, KVM only needs to wake the receiving
VCPU. Interrupt delivery is then handled by the SIGP
interpretation facility.
KVM wrongfuly assumed it also needs to request injection for the
external call interrupt after the respective intercept, causing
the interrupt to be delivered twice: once through the SIGP
interpretation facility and once through the interrupt injection
control by KVM.
Solution: Add appropriate special handling for 108 external call
intercepts.
Reproduction: 0. Apply kvm-unit-test submitted upstream
("[kvm-unit-tests PATCH v1 0/4] s390x: add tests for SIGP
call orders in enabled wait").
1. Run the smp_PV kvm-unit-test:
./run_tests.sh smp_PV
2. Check logs/smp_PV.log. If system is affected, the following
line can be found:
ABORT: smp: psw wait: ecall: Unexpected external call \
interrupt (code 0x1202): on cpu 1 at 0x11958
If the system is not affected, the line should look like
this:
PASS: smp: psw wait: ecall: received
Preventive: yes
Author: Nico Boehr <n...@linux.ibm.com>
Component: kernel
** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: Skipper Bug Screeners (skipper-screen-team)
Status: New
** Tags: architecture-s39064 bugnameltc-199408 severity-medium
targetmilestone-inin---
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[UBUNTU 20.04] KVM: PV: ext call delivered twice when receiver in PSW wait
https://bugs.launchpad.net/bugs/1995941
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