linux-kernel - Re: [RFC PATCH v5 032/104] KVM: x86/mmu: introduce config for PRIVATE KVM MMU

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Message-ID: <5093bff2-bc85-57b9-5f8b-ecb81417409e@redhat.com>
Date:   Tue, 5 Apr 2022 15:48:29 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Kai Huang <kai.huang@...el.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>
Cc:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jim Mattson <jmattson@...gle.com>,
        erdemaktas@...gle.com, Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH v5 032/104] KVM: x86/mmu: introduce config for PRIVATE
 KVM MMU

On 4/1/22 04:13, Kai Huang wrote:
>> I don't want to use CONFIG_INTEL_TDX_HOST in KVM MMU code.  I think the change
>> to KVM MMU should be a sort of independent from TDX.  But it seems failed based
>> on your feedback.
> 
> Why do you need to use any config?  As I said majority of your changes to MMU
> are not under any config.  But I'll leave this to maintainer/reviewers.

There are few uses, but the effect should be pretty large, because the 
config symbol replaces variable accesses with constants:

+static inline gfn_t kvm_gfn_stolen_mask(struct kvm *kvm)
+{
+#ifdef CONFIG_KVM_MMU_PRIVATE
+	return kvm->arch.gfn_shared_mask;
+#else
+	return 0;
+#endif
+}

Please keep it.

Paolo