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Date:   Thu, 19 Jan 2023 17:57:45 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     Yu Zhang <yu.c.zhang@linux.intel.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, Michal Luczaj <mhal@rbox.co>,
        David Woodhouse <dwmw@amazon.co.uk>
Subject: Re: [PATCH] KVM: x86: fix deadlock for KVM_XEN_EVTCHN_RESET
Message-ID: <Y8mEmSESlcdgtVg4@google.com>
References: <20221228110410.1682852-1-pbonzini@redhat.com>
 <20230119155800.fiypvvzoalnfavse@linux.intel.com>
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On Thu, Jan 19, 2023, Yu Zhang wrote:
> Hi Paolo,
> 
> > diff --git a/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c b/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
> > index 721f6a693799..dae510c263b4 100644
> > --- a/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
> > +++ b/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
> > @@ -962,6 +962,12 @@ int main(int argc, char *argv[])
> >  	}
> >  
> >   done:
> > +	struct kvm_xen_hvm_attr evt_reset = {
> > +		.type = KVM_XEN_ATTR_TYPE_EVTCHN,
> > +		.u.evtchn.flags = KVM_XEN_EVTCHN_RESET,
> > +	};
> > +	vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &evt_reset);
> > +
> >  	alarm(0);
> >  	clock_gettime(CLOCK_REALTIME, &max_ts);
> >  
> 
> This change generates a build failure with error message: 
> "error: a label can only be part of a statement and a declaration is not a statement".

And other flavors too, e.g.

x86_64/xen_shinfo_test.c:965:2: error: expected expression
        struct kvm_xen_hvm_attr evt_reset = {
        ^
x86_64/xen_shinfo_test.c:969:38: error: use of undeclared identifier 'evt_reset'
        vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &evt_reset);
                                            ^
x86_64/xen_shinfo_test.c:969:38: error: use of undeclared identifier 'evt_reset'
3 errors generated.
make: *** [../lib.mk:145: tools/testing/selftests/kvm/x86_64/xen_shinfo_test] Error 1
make: *** Waiting for unfinished jobs....

I'm surprised bots haven't complained about this, haven't seen any reports.

> Moving the definition of evt_reset to the beginning of main() can fix it:

I'll queue a patch, this is already in Linus' tree and I've collected a few other
tiny fixes for v6.2-rcwhatever that I'll send to Paolo.

Thanks!