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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Sean Christopherson <sean.j.christopherson@intel.com>,
        "Luck\, Tony" <tony.luck@intel.com>
Cc:     Mark D Rustad <mrustad@gmail.com>,
        Arvind Sankar <nivedita@alum.mit.edu>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        "Yu\, Fenghua" <fenghua.yu@intel.com>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        H Peter Anvin <hpa@zytor.com>,
        "Raj\, Ashok" <ashok.raj@intel.com>,
        "Shankar\, Ravi V" <ravi.v.shankar@intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>
Subject: Re: [PATCH v17] x86/split_lock: Enable split lock detection by kernel
In-Reply-To: <20200204000449.GA28014@linux.intel.com>
References: <4E95BFAA-A115-4159-AA4F-6AAB548C6E6C@gmail.com> <C3302B2F-177F-4C39-910E-EADBA9285DD0@intel.com> <8CC9FBA7-D464-4E58-8912-3E14A751D243@gmail.com> <20200126200535.GB30377@agluck-desk2.amr.corp.intel.com> <20200204000449.GA28014@linux.intel.com>
Date:   Tue, 04 Feb 2020 12:52:31 +0000
Message-ID: <87v9omy0og.fsf@nanos.tec.linutronix.de>
MIME-Version: 1.0
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Sender: linux-kernel-owner@vger.kernel.org
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Sean Christopherson <sean.j.christopherson@intel.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