5450203719
A guest which has configured the per-vCPU upcall vector may set the
HVM_PARAM_CALLBACK_IRQ param to fairly much anything other than zero.
For example, Linux v6.0+ after commit b1c3497e604 ("x86/xen: Add support
for HVMOP_set_evtchn_upcall_vector") will just do this after setting the
vector:
/* Trick toolstack to think we are enlightened. */
if (!cpu)
rc = xen_set_callback_via(1);
That's explicitly setting the delivery to GSI#1, but it's supposed to be
overridden by the per-vCPU vector setting. This mostly works in Qemu
*except* for the logic to enable the in-kernel handling of event channels,
which falsely determines that the kernel cannot accelerate GSI delivery
in this case.
Add a kvm_xen_has_vcpu_callback_vector() to report whether vCPU#0 has
the vector set, and use that in xen_evtchn_set_callback_param() to
enable the kernel acceleration features even when the param *appears*
to be set to target a GSI.
Preserve the Xen behaviour that when HVM_PARAM_CALLBACK_IRQ is set to
*zero* the event channel delivery is disabled completely. (Which is
what that bizarre guest behaviour is working round in the first place.)
Cc: qemu-stable@nongnu.org
Fixes:
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||
|---|---|---|
| .. | ||
| accel-blocker.h | ||
| accel-ops.h | ||
| arch_init.h | ||
| balloon.h | ||
| block-backend-common.h | ||
| block-backend-global-state.h | ||
| block-backend-io.h | ||
| block-backend.h | ||
| block-ram-registrar.h | ||
| blockdev.h | ||
| cpu-throttle.h | ||
| cpu-timers.h | ||
| cpus.h | ||
| cryptodev-vhost-user.h | ||
| cryptodev-vhost.h | ||
| cryptodev.h | ||
| device_tree.h | ||
| dirtylimit.h | ||
| dirtyrate.h | ||
| dma.h | ||
| dump-arch.h | ||
| dump.h | ||
| event-loop-base.h | ||
| hax.h | ||
| hostmem.h | ||
| hvf.h | ||
| hvf_int.h | ||
| hw_accel.h | ||
| iothread.h | ||
| kvm.h | ||
| kvm_int.h | ||
| kvm_xen.h | ||
| memory_mapping.h | ||
| numa.h | ||
| nvmm.h | ||
| os-posix.h | ||
| os-win32.h | ||
| qtest.h | ||
| replay.h | ||
| reset.h | ||
| rng-random.h | ||
| rng.h | ||
| rtc.h | ||
| runstate-action.h | ||
| runstate.h | ||
| seccomp.h | ||
| stats.h | ||
| sysemu.h | ||
| tcg.h | ||
| tpm.h | ||
| tpm_backend.h | ||
| tpm_util.h | ||
| vhost-user-backend.h | ||
| watchdog.h | ||
| whpx.h | ||
| xen-mapcache.h | ||
| xen.h | ||