From: Paolo Bonzini <pbonzini@redhat.com>
To: Andy Lutomirski <luto@amacapital.net>, Borislav Petkov <bp@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, X86 ML <x86@kernel.org>,
Minfei Huang <mnghuan@gmail.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH] Cleanup __pvclock_read_cycles to remove useless variables
Date: Wed, 11 May 2016 16:24:37 +0200 [thread overview]
Message-ID: <573340A5.1090209@redhat.com> (raw)
In-Reply-To: <CALCETrVwn_bqeuuv7UbZzr8T2M+krjaDNgrqWd3vX0gujPm5sA@mail.gmail.com>
On 30/04/2016 23:57, Andy Lutomirski wrote:
>> > Should we kill __pvclock_read_cycles in favor of vread_pvclock? It looks
>> > doable at a quick scan...
>> >
> The in-kernel version might have to be a bit different because it
> needs to handle the !stable case. If !stable, it should just use the
> current CPU's copy which means that, realistically, it should just
> get_cpu and use the local copy unconditionally. Other than that, it
> could look a lot like the vread_pvclock variant.
>
> But I agree, the current thing is incomprehensible.
It also lacks smp_rmb()s. One is more or less implicit in rdtsc, but
you need one to separate __pvclock_read_cycles's reads of src->foo from
pvclock_read_flags's read of src->version.
Minfei, would you like to take a look?
Paolo
next prev parent reply other threads:[~2016-05-11 14:24 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-25 6:53 [PATCH] Cleanup __pvclock_read_cycles to remove useless variables Minfei Huang
2016-04-30 10:12 ` Minfei Huang
2016-04-30 13:24 ` Borislav Petkov
2016-04-30 17:47 ` Andy Lutomirski
2016-04-30 19:17 ` Borislav Petkov
2016-04-30 21:57 ` Andy Lutomirski
2016-05-11 14:24 ` Paolo Bonzini [this message]
2016-05-11 15:19 ` Minfei Huang
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