linux-kernel - Re: [RFC PATCH v5 033/104] KVM: x86: Add infrastructure for stolen GPA bits

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Message-ID: <240599a4-47f0-fe7e-1270-5ec7fbc0da0b@redhat.com>
Date:   Tue, 5 Apr 2022 16:02:02 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Isaku Yamahata <isaku.yamahata@...il.com>,
        Kai Huang <kai.huang@...el.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>,
        Chao Peng <chao.p.peng@...ux.intel.com>
Subject: Re: [RFC PATCH v5 033/104] KVM: x86: Add infrastructure for stolen
 GPA bits

On 4/1/22 04:34, Isaku Yamahata wrote:
> Sure, this patch heavily changed from the original patch Now.  One suggestion
> is that private/shared is characteristic to kvm page fault, not gpa/gfn.
> It's TDX specific.
> 
> - Add a helper function to check if KVM MMU is TD or VM. Right now
>    kvm_gfn_stolen_mask() is used.  Probably kvm_mmu_has_private_bit().
>    (any better name?)

I think use of kvm_gfn_stolen_mask() should be minimized anyway.  I 
would rename it to to kvm_{gfn,gpa}_private_mask and not return bool.

> - Let's keep address conversion functions: address => unalias/shared/private

unalias is the same as private.  It doesn't seem to have a lot of uses. 
  I would just inline "x & ~gfn_private_mask", or "x & 
~kvm_gfn_private_mask(kvm)"; or the same with gpa of course.

The shared and private conversion functions should remain.

> - Add struct kvm_page_fault.is_private
>    see how kvm_is_private_{gpa, gfn}() can be removed (or reduced).

Agreed.

Paolo