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i386/xen: Implement SCHEDOP_poll and SCHEDOP_yield

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They both do the same thing and just call sched_yield. This is enough to
stop the Linux guest panicking when running on a host kernel which doesn't
intercept SCHEDOP_poll and lets it reach userspace.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
This commit is contained in:
David Woodhouse 2022-12-14 21:50:41 +00:00
parent 79b7067dc6
commit c789b9ef5f
1 changed files with 13 additions and 0 deletions
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13
target/i386/kvm/xen-emu.c
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@ -234,6 +234,19 @@ static bool kvm_xen_hcall_sched_op(struct kvm_xen_exit *exit, X86CPU *cpu,
err = schedop_shutdown(cs, arg); err = schedop_shutdown(cs, arg);
break; break;
case SCHEDOP_poll:
/*
* Linux will panic if this doesn't work. Just yield; it's not
* worth overthinking it because with event channel handling
* in KVM, the kernel will intercept this and it will never
* reach QEMU anyway. The semantics of the hypercall explicltly
* permit spurious wakeups.
*/
case SCHEDOP_yield:
sched_yield();
err = 0;
break;
default: default:
return false; return false;
} }