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xics/spapr: Detect old KVM XICS on POWER9 hosts

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Older KVMs on POWER9 don't support destroying/recreating a KVM XICS
device, which is required by 'dual' interrupt controller mode. This
causes QEMU to emit a warning when the guest is rebooted and to fall
back on XICS emulation:

qemu-system-ppc64: warning: kernel_irqchip allowed but unavailable:
 Error on KVM_CREATE_DEVICE for XICS: File exists

If kernel irqchip is required, QEMU will thus exit when the guest is
first rebooted. Failing QEMU this late may be a painful experience
for the user.

Detect that and exit at machine init instead.

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <156044430517.125694.6207865998817342638.stgit@bahia.lab.toulouse-stg.fr.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Greg Kurz 2019-06-13 18:45:05 +02:00 • committed by David Gibson
parent d9293c4843
commit 7abc0c6d35
4 changed files with 46 additions and 2 deletions
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4
docs/specs/ppc-spapr-xive.rst
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@ -142,8 +142,8 @@ xics XICS KVM XICS emul. XICS KVM
(3) QEMU fails at CAS with ``Guest requested unavailable interrupt
mode (XICS), either don't set the ic-mode machine property or try
ic-mode=xics or ic-mode=dual``
(4) QEMU/KVM incompatibility due to device destruction in reset. This
needs to be addressed more cleanly with an error.
(4) QEMU/KVM incompatibility due to device destruction in reset. QEMU fails
with ``KVM is too old to support ic-mode=dual,kernel-irqchip=on``
XIVE Device tree properties