Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 18 Dec 2019 16:58:57 -0500
From:   Peter Xu <peterx@redhat.com>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Sean Christopherson <sean.j.christopherson@intel.com>,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        "Tian, Kevin" <kevin.tian@intel.com>
Subject: Re: [PATCH RFC 04/15] KVM: Implement ring-based dirty memory tracking
Message-ID: <20191218215857.GE26669@xz-x1>
References: <20191209215400.GA3352@xz-x1>
 <affd9d84-1b84-0c25-c431-a075c58c33dc@redhat.com>
 <20191210155259.GD3352@xz-x1>
 <3e6cb5ec-66c0-00ab-b75e-ad2beb1d216d@redhat.com>
 <20191215172124.GA83861@xz-x1>
 <f117d46a-7528-ce32-8e46-4f3f35937079@redhat.com>
 <20191216185454.GG83861@xz-x1>
 <815923d9-2d48-2915-4acb-97eb90996403@redhat.com>
 <20191217162405.GD7258@xz-x1>
 <c01d0732-2172-2573-8251-842e94da4cfc@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <c01d0732-2172-2573-8251-842e94da4cfc@redhat.com>
User-Agent: Mutt/1.12.1 (2019-06-15)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Dec 17, 2019 at 05:28:54PM +0100, Paolo Bonzini wrote:
> 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

Well, now I've changed my mind. :) (considering that we still have
many places that will not have vcpu*...)

I can simply add that "vcpu_smm" parameter to kvm_vcpu_write_*()
without removing the kvm_write_*() helpers.  Then I'll be able to
convert most of the kvm_write_*() (or its family) callers to
kvm_vcpu_write*(..., vcpu_smm=false) calls where proper.

Would that be good?

-- 
Peter Xu