Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 4 May 2021 20:36:09 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Ben Gardon <bgardon@google.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, Peter Xu <peterx@redhat.com>,
        Peter Shier <pshier@google.com>,
        Junaid Shahid <junaids@google.com>,
        Jim Mattson <jmattson@google.com>,
        Yulei Zhang <yulei.kernel@gmail.com>,
        Wanpeng Li <kernellwp@gmail.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Xiao Guangrong <xiaoguangrong.eric@gmail.com>
Subject: Re: [PATCH v2 1/7] KVM: x86/mmu: Track if shadow MMU active
Message-ID: <YJGwOfzTtj4kJIVp@google.com>
References: <20210429211833.3361994-1-bgardon@google.com>
 <20210429211833.3361994-2-bgardon@google.com>
 <YJGmpOzaFy9E0f5T@google.com>
 <edfadb98-b86e-6d03-bdfc-9025fac73dee@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <edfadb98-b86e-6d03-bdfc-9025fac73dee@redhat.com>
Precedence: bulk

On Tue, May 04, 2021, Paolo Bonzini wrote:
> On 04/05/21 21:55, Sean Christopherson wrote:
> > But, I think we we can avoid bikeshedding by simply eliminating this flag.  More
> > in later patches.
> 
> Are you thinking of checking slot->arch.rmap[0] directly?  That should work
> indeed.
> 
> > > -	kvm_mmu_init_tdp_mmu(kvm);
> > > +	if (!kvm_mmu_init_tdp_mmu(kvm))
> > > +		activate_shadow_mmu(kvm);
> > Doesn't come into play yet, but I would strongly prefer to open code setting the
> > necessary flag instead of relying on the helper to never fail.
> > 
> 
> You mean
> 
> kvm->arch.shadow_mmu_active = !kvm_mmu_init_tdp_mmu(kvm);
> 
> (which would assign to alloc_memslot_rmaps instead if shadow_mmu_active is
> removed)?  That makes sense.

Ya, that or:

	if (kvm_mmu_init_tdp_mmu(kvm))
		kvm->arch.memslots_have_rmaps = true;

I don't have a preference between the two variants.