linux-kernel - Re: [PATCH 2/2] x86/vdso: Add VCLOCK

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Message-ID: <87d1eqqlkv.fsf@vitty.brq.redhat.com>
Date:   Fri, 10 Feb 2017 13:25:36 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Stephen Hemminger <sthemmin@...rosoft.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "x86\@kernel.org" <x86@...nel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "KY Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "devel\@linuxdriverproject.org" <devel@...uxdriverproject.org>,
        "virtualization\@lists.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH 2/2] x86/vdso: Add VCLOCK_HVCLOCK vDSO clock read method

Stephen Hemminger <sthemmin@...rosoft.com> writes:

> Why not use existing seqlock's?
>

To be honest I don't quite understand how we could use it -- the
sequence locking here is done against the page updated by the
hypersior, we're not creating new structures (so I don't understand how
we could use struct seqcount which we don't have) but I may be
misunderstanding something.

BTW, I just occured to me that I should've probably put the TSC reading
code to mshyperv.h and use it from both vDSO and read_hv_clock_tsc() --
what do you thing?

[snip]

-- 
  Vitaly