linux-kernel - Re: [PATCH v4 2/2] xen: delay xen_hvm_init_time

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Date:   Wed, 2 Mar 2022 19:08:11 -0800
From:   Dongli Zhang <dongli.zhang@...cle.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, jgross@...e.com,
        sstabellini@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, joe.jin@...cle.com
Subject: Re: [PATCH v4 2/2] xen: delay xen_hvm_init_time_ops() if kdump is
 boot on vcpu>=32

Hi Boris,

On 3/2/22 6:11 PM, Boris Ostrovsky wrote:
> 
> On 3/2/22 7:31 PM, Dongli Zhang wrote:
>> Hi Boris,
>>
>> On 3/2/22 4:20 PM, Boris Ostrovsky wrote:
>>> On 3/2/22 11:40 AM, Dongli Zhang wrote:
>>>>    void __init xen_hvm_init_time_ops(void)
>>>>    {
>>>> +    static bool hvm_time_initialized;
>>>> +
>>>> +    if (hvm_time_initialized)
>>>> +        return;
>>>> +
>>>>        /*
>>>>         * vector callback is needed otherwise we cannot receive interrupts
>>>>         * on cpu > 0 and at this point we don't know how many cpus are
>>>>         * available.
>>>>         */
>>>>        if (!xen_have_vector_callback)
>>>> -        return;
>>>> +        goto exit;
>>>
>>> Why not just return? Do we expect the value of xen_have_vector_callback to
>>> change?
>> I just want to keep above sync with ....
>>
>>>
>>> -boris
>>>
>>>
>>>>          if (!xen_feature(XENFEAT_hvm_safe_pvclock)) {
>>>>            pr_info("Xen doesn't support pvclock on HVM, disable pv timer");
>>>> +        goto exit;
>>>> +    }
>> ... here.
>>
>> That is, I want the main logic of xen_hvm_init_time_ops() to run for at most
>> once. Both of above two if statements will "go to exit".
> 
> 
> I didn't notice this actually.
> 
> 
> I think both of them should return early, there is no reason to set
> hvm_time_initialized to true when, in fact, we have not initialized anything.
> And to avoid printing the warning twice we can just replace it with pr_info_once().
> 
> 
> I can fix it up when committing so no need to resend. So unless you disagree

Thank you very much for fixing it during committing.

Dongli Zhang