linux-kernel - Re: [PATCH] KVM: nVMX: Fix some comment typos and coding style

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Message-ID: <bc72431b89444fa3a127cf71065f71db@huawei.com>
Date:   Fri, 7 Feb 2020 04:05:36 +0000
From:   linmiaohe <linmiaohe@...wei.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "wanpengli@...cent.com" <wanpengli@...cent.com>,
        "jmattson@...gle.com" <jmattson@...gle.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "hpa@...or.com" <hpa@...or.com>
Subject: Re: [PATCH] KVM: nVMX: Fix some comment typos and coding style

Hi:
Sean Christopherson <sean.j.christopherson@...el.com> wrote:
> On Thu, Feb 06, 2020 at 12:32:38PM +0100, Vitaly Kuznetsov wrote:
>> linmiaohe <linmiaohe@...wei.com> writes:
>> 
>> 
>> I have to admit that shadow MMU in KVM is not my strong side but this 
>> comment reads weird, I'd appreciate if someone could suggest a better 
>> alternative.
>
>	/* One off flag for a stupid corner case in shadow paging. */
>> 
>> >  	 */
>
>	/*
>	 * Indicates the guest is trying to write a gfn that contains one or
>	 * more of the PTEs used to translate the write itself, i.e. the access
>	 * is changing its own translation in the guest page tables.  KVM exits
>	 * to userspace if emulation of the faulting instruction fails and this
>	 * flag is set, as KVM cannot make forward progress.
>	 *
>	 * If emulation fails for a write to guest page tables, KVM unprotects
>	 * (zaps) the shadow page for the target gfn and resumes the guest to
>	 * retry the non-emulatable instruction (on hardware).  Unprotecting the
>	 * gfn doesn't allow forward progress for a self-changing access because
>	 * doing so also zaps the translation for the gfn, i.e. retrying the
>	 * instruction will hit a !PRESENT fault, which results in a new shadow
>	 * page and sends KVM back to square one.
>	 */
>> >  	bool write_fault_to_shadow_pgtable;

Thanks for your detail comment. This field confused me once.

Thanks to both for review! Will send v2.