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

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Message-ID: <20200206153546.GB13067@linux.intel.com>
Date:   Thu, 6 Feb 2020 07:35:46 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     linmiaohe <linmiaohe@...wei.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, x86@...nel.org, pbonzini@...hat.com,
        rkrcmar@...hat.com, wanpengli@...cent.com, jmattson@...gle.com,
        joro@...tes.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com
Subject: Re: [PATCH] KVM: nVMX: Fix some comment typos and coding style

On Thu, Feb 06, 2020 at 12:32:38PM +0100, Vitaly Kuznetsov wrote:
> linmiaohe <linmiaohe@...wei.com> writes:
> 
> > From: Miaohe Lin <linmiaohe@...wei.com>
> >
> > Fix some typos in the comments. Also fix coding style.
> >
> > Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> > ---
> >  arch/x86/include/asm/kvm_host.h | 2 +-
> >  arch/x86/kvm/vmx/nested.c       | 5 +++--
> >  2 files changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 4dffbc10d3f8..8196a4a0df8b 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -782,7 +782,7 @@ struct kvm_vcpu_arch {
> >  
> >  	/*
> >  	 * Indicate whether the access faults on its page table in guest
> 
> Indicates?
> 
> > -	 * which is set when fix page fault and used to detect unhandeable
> > +	 * which is set when fix page fault and used to detect unhandleable
> >  	 * instruction.
> 
> 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;