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:
|
||
|---|---|---|
| .. | ||
| hax | ||
| hvf | ||
| kvm | ||
| nvmm | ||
| tcg | ||
| whpx | ||
| arch_dump.c | ||
| arch_memory_mapping.c | ||
| cpu-dump.c | ||
| cpu-internal.h | ||
| cpu-param.h | ||
| cpu-qom.h | ||
| cpu-sysemu.c | ||
| cpu.c | ||
| cpu.h | ||
| gdbstub.c | ||
| helper.c | ||
| helper.h | ||
| host-cpu.c | ||
| host-cpu.h | ||
| Kconfig | ||
| machine.c | ||
| meson.build | ||
| monitor.c | ||
| ops_sse.h | ||
| sev-sysemu-stub.c | ||
| sev.c | ||
| sev.h | ||
| svm.h | ||
| trace-events | ||
| trace.h | ||
| xsave_helper.c | ||