apic-split / x2apic test in kvm-unit-test failed (FAIL: PV IPIs testing)

Issue found with kvm-unit-test repo updated to d8a4f9e5 (ci: Update the list of tests that we run in the Fedora Cirrus-CI).

Unlike the result on 3.13 and 4.4 kernel, which timeout in the end (bug 1748103)

Test failed with just one failure on AMD64 node exotic-skunk with Bionic 4.15 kernel:
  FAIL: PV IPIs testing

Test log:
 Running '/home/ubuntu/autotest/client/tmp/ubuntu_kvm_unit_tests/src/kvm-unit-tests/tests/apic'
 BUILD_HEAD=63cdb04b
 timeout -k 1s --foreground 30 /usr/bin/qemu-system-x86_64 --no-reboot -nodefaults -device pc-testdev -device isa-debug-exit,iobase=0xf4,iosize=0x4 -vnc none -serial stdio -device pci-testdev -machine accel=kvm -kernel /tmp/tmp.Ek2vxrGPNJ -smp 2 -cpu qemu64,+x2apic,+tsc-deadline # -initrd /tmp/tmp.UYCbRGrCF6
 qemu-system-x86_64: warning: host doesn't support requested feature: CPUID.80000001H:ECX.svm [bit 2]
 qemu-system-x86_64: warning: host doesn't support requested feature: CPUID.80000001H:ECX.svm [bit 2]
 enabling apic
 smp: waiting for 1 APs
 enabling apic
 setup: CPU 1 online
 paging enabled
 cr0 = 80010011
 cr3 = 1007000
 cr4 = 20
 apic version: 14
 PASS: apic existence
 PASS: xapic id matches cpuid
 PASS: writeable xapic id
 PASS: non-writeable x2apic id
 PASS: sane x2apic id
 PASS: x2apic id matches cpuid
 PASS: correct xapic id after reset
 PASS: apic_disable: Local apic disabled
 PASS: apic_disable: CPUID.1H:EDX.APIC[bit 9] is clear
 PASS: apic_disable: *0xfee00030: ffffffff
 PASS: apic_disable: CR8: 0
 PASS: apic_disable: CR8: f
 PASS: apic_disable: *0xfee00080: ffffffff
 PASS: apic_disable: Local apic enabled in xAPIC mode
 PASS: apic_disable: CPUID.1H:EDX.APIC[bit 9] is set
 PASS: apic_disable: *0xfee00030: 50014
 PASS: apic_disable: *0xfee00080: 0
 PASS: apic_disable: *0xfee00080: f0
 PASS: apic_disable: Local apic enabled in x2APIC mode
 PASS: apic_disable: CPUID.1H:EDX.APIC[bit 9] is set
 PASS: apic_disable: *0xfee00030: ffffffff
 PASS: apic_disable: CR8: 0
 PASS: apic_disable: CR8: f
 PASS: apic_disable: *0xfee00080: ffffffff
 x2apic enabled
 PASS: x2apic enabled to invalid state
 PASS: x2apic enabled to apic enabled
 PASS: x2apic enabled to disabled state
 PASS: disabled to invalid state
 PASS: disabled to x2apic enabled
 PASS: apic disabled to apic enabled
 PASS: apic enabled to invalid state
 PASS: apicbase: relocate apic
 PASS: apicbase: reserved physaddr bits
 PASS: apicbase: reserved low bits
 PASS: self_ipi_xapic: Local apic enabled in xAPIC mode
 PASS: self_ipi_xapic: self ipi
 PASS: self_ipi_x2apic: Local apic enabled in x2APIC mode
 PASS: self_ipi_x2apic: self ipi
 starting broadcast (x2apic)
 PASS: APIC physical broadcast address
 PASS: APIC physical broadcast shorthand
 FAIL: PV IPIs testing
 PASS: nmi-after-sti
 PASS: multiple nmi
 PASS: pending nmi
 PASS: APIC LVT timer one shot
 starting apic change mode
 PASS: TMICT value reset
 PASS: TMCCT should have a non-zero value
 PASS: TMCCT should have reached 0
 PASS: TMCCT should have a non-zero value
 PASS: TMCCT should not be reset to TMICT value
 PASS: TMCCT should be reset to the initial-count
 PASS: TMCCT should not be reset to init
 PASS: TMCCT should have reach zero
 PASS: TMCCT should stay at zero
 PASS: tsc deadline timer
 PASS: tsc deadline timer clearing
 SUMMARY: 56 tests, 1 unexpected failures
 FAIL apic (56 tests, 1 unexpected failures)