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Subject: Re: [PATCH v2] xen/events: remove event handling recursion detection
To:     Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org
Cc:     Stefano Stabellini <sstabellini@kernel.org>
References: <20191128084545.13831-1-jgross@suse.com>
 <b0a86e66-2366-ff94-e867-2fc5cfdae38d@oracle.com>
From:   =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= <jgross@suse.com>
Message-ID: <6483de2d-963c-3b5e-150a-641e070e3d0e@suse.com>
Date:   Fri, 29 Nov 2019 06:59:12 +0100
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On 28.11.19 22:37, Boris Ostrovsky wrote:
> On 11/28/19 3:45 AM, Juergen Gross wrote:
>> -
>>   static void __xen_evtchn_do_upcall(void)
>>   {
>>   	struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
>> -	int cpu = get_cpu();
>> -	unsigned count;
>> +	int cpu = smp_processor_id();
>>   
>>   	do {
>>   		vcpu_info->evtchn_upcall_pending = 0;
>>   
>> -		if (__this_cpu_inc_return(xed_nesting_count) - 1)
>> -			goto out;
>> -
>>   		xen_evtchn_handle_events(cpu);
>>   
>>   		BUG_ON(!irqs_disabled());
>>   
>> -		count = __this_cpu_read(xed_nesting_count);
>> -		__this_cpu_write(xed_nesting_count, 0);
>> -	} while (count != 1 || vcpu_info->evtchn_upcall_pending);
>> -
>> -out:
>> +		rmb(); /* Hypervisor can set upcall pending. */
> 
> virt_rmb() perhaps then?

Yes, that's better.


Juergen