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From:   Thomas Gleixner <tglx@linutronix.de>
To:     David Laight <David.Laight@ACULAB.COM>,
        'Sasha Levin' <sashal@kernel.org>
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        Andrew Cooper <andrew.cooper3@citrix.com>,
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Subject: RE: [PATCH v12 10/18] x86/fsgsbase/64: Enable FSGSBASE instructions in helper functions
In-Reply-To: <238a6e2609eb4e0497b13fbe5f531917@AcuMS.aculab.com>
References: <20200511045311.4785-11-sashal@kernel.org> <87v9ktw1ev.fsf@nanos.tec.linutronix.de> <20200518202435.GD33628@sasha-vm> <238a6e2609eb4e0497b13fbe5f531917@AcuMS.aculab.com>
Date:   Tue, 19 May 2020 16:48:05 +0200
Message-ID: <87r1vg6kwq.fsf@nanos.tec.linutronix.de>
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David Laight <David.Laight@ACULAB.COM> writes:
> From: Sasha Levin
>> >> +		native_swapgs();
>> >> +		gsbase = rdgsbase();
>> >> +		native_swapgs();
>
> Does local_irq_save() even do anything useful here.
> You need to actually execute CLI, not just set a
> flag that indicates interrupts shouldn't happen.
> (Which is what I think local_irq_save() might do.)

  local_irq_save()
    raw_local_irq_save()
      arch_local_irq_save()
        arch_local_irq_disable()
          native_irq_disable()
            asm("CLI")

> You also (probably) need to disable NMIs.

The NMI entry can deal with that obviously.

Thanks,

        tglx