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Message-ID: <6fb0889f-090d-740b-8ace-8b95b97ebf71@redhat.com>
Date:   Tue, 5 Apr 2022 16:10:25 +0200
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Subject: Re: [RFC PATCH v5 037/104] KVM: x86/mmu: Allow non-zero init value
 for shadow PTE
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To:     isaku.yamahata@intel.com, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     isaku.yamahata@gmail.com, Jim Mattson <jmattson@google.com>,
        erdemaktas@google.com, Connor Kuehl <ckuehl@redhat.com>,
        Sean Christopherson <seanjc@google.com>
References: <cover.1646422845.git.isaku.yamahata@intel.com>
 <b74b3660f9d16deafe83f2670539a8287bef988f.1646422845.git.isaku.yamahata@intel.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
In-Reply-To: <b74b3660f9d16deafe83f2670539a8287bef988f.1646422845.git.isaku.yamahata@intel.com>
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On 3/4/22 20:48, isaku.yamahata@intel.com wrote:
>   static void mmu_spte_clear_no_track(u64 *sptep)
>   {
> -	__update_clear_spte_fast(sptep, 0ull);
> +	__update_clear_spte_fast(sptep, shadow_init_value);
>   }
>   

Please WARN_ON_ONCE if shadow_init_value is nonzero, and then keep 0ull 
as the argument.

I have not thought much of the steps that are needed if were to flip 
both bit 0 and bit 63, so let's at least document that with a WARN.

Otherwise,

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Paolo