linux-kernel - Re: [PATCH RFC 04/15] KVM: Implement ring-based dirty memory tracking

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Date:   Tue, 17 Dec 2019 17:28:54 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        "Tian, Kevin" <kevin.tian@...el.com>
Subject: Re: [PATCH RFC 04/15] KVM: Implement ring-based dirty memory tracking

On 17/12/19 17:24, Peter Xu wrote:
>> No, please pass it all the way down to the [&] functions but not to
>> kvm_write_guest_page.  Those should keep using vcpu->kvm.
> Actually I even wanted to refactor these helpers.  I mean, we have two
> sets of helpers now, kvm_[vcpu]_{read|write}*(), so one set is per-vm,
> the other set is per-vcpu.  IIUC the only difference of these two are
> whether we should consider ((vcpu)->arch.hflags & HF_SMM_MASK) or we
> just write to address space zero always.

Right.

> Could we unify them into a
> single set of helper (I'll just drop the *_vcpu_* helpers because it's
> longer when write) but we always pass in vcpu* as the first parameter?
> Then we add another parameter "vcpu_smm" to show whether we want to
> consider the HF_SMM_MASK flag.

You'd have to check through all KVM implementations whether you always
have the vCPU.  Also non-x86 doesn't have address spaces, and by the
time you add ", true" or ", false" it's longer than the "_vcpu_" you
have removed.  So, not a good idea in my opinion. :D

Paolo