linux-kernel - Re: [PATCH v17] x86/split_lock: Enable split lock detection by kernel

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Message-ID: <87v9omy0og.fsf@nanos.tec.linutronix.de>
Date:   Tue, 04 Feb 2020 12:52:31 +0000
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        "Luck\, Tony" <tony.luck@...el.com>
Cc:     Mark D Rustad <mrustad@...il.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Yu\, Fenghua" <fenghua.yu@...el.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        "Raj\, Ashok" <ashok.raj@...el.com>,
        "Shankar\, Ravi V" <ravi.v.shankar@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v17] x86/split_lock: Enable split lock detection by kernel

Sean Christopherson <sean.j.christopherson@...el.com> writes:

> On Sun, Jan 26, 2020 at 12:05:35PM -0800, Luck, Tony wrote:
>
> ...
>
>> +bool handle_user_split_lock(struct pt_regs *regs, long error_code)
>
> No reason to take the error code unless there's a plan to use it.
>
>> +{
>> +	if ((regs->flags & X86_EFLAGS_AC) || sld_state == sld_fatal)
>> +		return false;
>
> Any objection to moving the EFLAGS.AC up to do_alignment_check()?  And
> take "unsigned long rip" instead of @regs?
>
> That would allow KVM to reuse handle_user_split_lock() for guest faults
> without any changes (other than exporting).
>
> E.g. do_alignment_check() becomes:
>
> 	if (!(regs->flags & X86_EFLAGS_AC) && handle_user_split_lock(regs->ip))
> 		return;

No objections.

Thanks,

        tglx