linux-kernel - RE: [PATCH V2 2/13] KVM/MMU: Add tlb flush with range helper function

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Message-ID: <CY4PR21MB0773253EB4F0CED66A9A6F6BDC1C0@CY4PR21MB0773.namprd21.prod.outlook.com>
Date:   Wed, 19 Sep 2018 16:07:18 +0000
From:   "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>
To:     Tianyu Lan <Tianyu.Lan@...rosoft.com>
CC:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        vkuznets <vkuznets@...hat.com>,
        Jork Loeser <Jork.Loeser@...rosoft.com>
Subject: RE: [PATCH V2 2/13] KVM/MMU: Add tlb flush with range helper function

From: Tianyu Lan  Sent: Monday, September 17, 2018 8:18 PM
>
> +static void kvm_flush_remote_tlbs_with_range(struct kvm *kvm,
> +		struct kvm_tlb_range *range)
> +{
> +	int ret = -ENOTSUPP;
> +
> +	if (range && kvm_x86_ops->tlb_remote_flush_with_range) {
> +		/*
> +		 * Read tlbs_dirty before setting KVM_REQ_TLB_FLUSH in
> +		 * kvm_make_all_cpus_request.
> +		 */
> +		long dirty_count = smp_load_acquire(&kvm->tlbs_dirty);
> +
> +		ret = kvm_x86_ops->tlb_remote_flush_with_range(kvm, range);
> +		cmpxchg(&kvm->tlbs_dirty, dirty_count, 0);
> +	}

The comment and the code that manipulates kvm->tlbs_dirty appears
to have been copied from kvm_flush_remote_tlbs().  But the above
code doesn't call kvm_make_all_cpus_request().   I haven't traced
all the details, but it seems like the comment should be updated,
or the code isn't needed.

Michael