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Date:   Thu, 19 Jan 2023 23:58:00 +0800
From:   Yu Zhang <yu.c.zhang@linux.intel.com>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        seanjc@google.com, 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: <20230119155800.fiypvvzoalnfavse@linux.intel.com>
References: <20221228110410.1682852-1-pbonzini@redhat.com>
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In-Reply-To: <20221228110410.1682852-1-pbonzini@redhat.com>
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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".

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

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 dae510c263b4..d71f1508bb21 100644
--- a/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
+++ b/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
@@ -623,6 +623,10 @@ int main(int argc, char *argv[])
        rs->state = 0x5a;

        bool evtchn_irq_expected = false;
+       struct kvm_xen_hvm_attr evt_reset = {
+               .type = KVM_XEN_ATTR_TYPE_EVTCHN,
+               .u.evtchn.flags = KVM_XEN_EVTCHN_RESET,
+       };

        for (;;) {
                volatile struct kvm_run *run = vcpu->run;
@@ -962,10 +966,6 @@ 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);

B.R.
Yu