linux-kernel - Re: [PATCH v5 3/4] x86/xen/time: setup vcpu 0 time info page

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Message-ID: <62e11cdf-5411-1692-1103-a436581411a6@oracle.com>
Date:   Mon, 2 Oct 2017 21:58:42 +0100
From:   Joao Martins <joao.m.martins@...cle.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Juergen Gross <jgross@...e.com>,
        Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH v5 3/4] x86/xen/time: setup vcpu 0 time info page



On 10/02/2017 07:44 PM, Boris Ostrovsky wrote:
> 
>> +
>> +static void xen_setup_vsyscall_time_info(void)
>> +{
>> +	struct vcpu_register_time_memory_area t;
>> +	struct pvclock_vsyscall_time_info *ti;
>> +	int ret;
> 
> 
> In the previous version you'd return immediately if
> PVCLOCK_TSC_STABLE_BIT was not set. Don't you still need to check this?
> Especially give...
> 
Yes, my mistake.

When moving the primary info check I changed the comment below, but should have
moved the call to xen_setup_vsyscall_time_info() into the newly added if ()
clause added in the previous patch. Let me move that inside the conditional and
respin in v6.

Joao

> 
>> +
>> +	ti = (struct pvclock_vsyscall_time_info *)get_zeroed_page(GFP_KERNEL);
>> +	if (!ti)
>> +		return;
>> +
>> +	t.addr.v = &ti->pvti;
>> +
>> +	ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area, 0, &t);
>> +	if (ret) {
>> +		pr_notice("xen: VCLOCK_PVCLOCK not supported (err %d)\n", ret);
>> +		free_page((unsigned long)ti);
>> +		return;
>> +	}
>> +
>> +	/*
>> +	 * If primary time info had this bit set, secondary should too since
> 
> ... this comment?
> 
> -boris