linux-kernel - Re: [PATCH 2/7] KVM: x86/mmu: Replace hardcoded value 0 for the initial value for SPTE

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Date: Wed, 15 May 2024 10:32:09 -0700
From: Isaku Yamahata <isaku.yamahata@...el.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Sean Christopherson <seanjc@...gle.com>,
	Isaku Yamahata <isaku.yamahata@...el.com>,
	Xiaoyao Li <xiaoyao.li@...el.com>,
	Binbin Wu <binbin.wu@...ux.intel.com>, rick.p.edgecombe@...el.com
Subject: Re: [PATCH 2/7] KVM: x86/mmu: Replace hardcoded value 0 for the
 initial value for SPTE

On Tue, May 07, 2024 at 11:44:54AM -0400,
Paolo Bonzini <pbonzini@...hat.com> wrote:

> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index c6192a52bd31..f5401967897a 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -603,7 +603,7 @@ static inline int tdp_mmu_zap_spte_atomic(struct kvm *kvm,
>  	 * here since the SPTE is going from non-present to non-present.  Use
>  	 * the raw write helper to avoid an unnecessary check on volatile bits.
>  	 */
> -	__kvm_tdp_mmu_write_spte(iter->sptep, 0);
> +	__kvm_tdp_mmu_write_spte(iter->sptep, SHADOW_NONPRESENT_VALUE);
>  
>  	return 0;
>  }
> @@ -740,8 +740,8 @@ static void __tdp_mmu_zap_root(struct kvm *kvm, struct kvm_mmu_page *root,
>  			continue;
>  
>  		if (!shared)
> -			tdp_mmu_iter_set_spte(kvm, &iter, 0);
> -		else if (tdp_mmu_set_spte_atomic(kvm, &iter, 0))
> +			tdp_mmu_iter_set_spte(kvm, &iter, SHADOW_NONPRESENT_VALUE);
> +		else if (tdp_mmu_set_spte_atomic(kvm, &iter, SHADOW_NONPRESENT_VALUE))
>  			goto retry;
>  	}
>  }
> @@ -808,8 +808,8 @@ bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
>  	if (WARN_ON_ONCE(!is_shadow_present_pte(old_spte)))
>  		return false;
>  
> -	tdp_mmu_set_spte(kvm, kvm_mmu_page_as_id(sp), sp->ptep, old_spte, 0,
> -			 sp->gfn, sp->role.level + 1);
> +	tdp_mmu_set_spte(kvm, kvm_mmu_page_as_id(sp), sp->ptep, old_spte,
> +			 SHADOW_NONPRESENT_VALUE, sp->gfn, sp->role.level + 1);
>  
>  	return true;
>  }
> @@ -843,7 +843,7 @@ static bool tdp_mmu_zap_leafs(struct kvm *kvm, struct kvm_mmu_page *root,
>  		    !is_last_spte(iter.old_spte, iter.level))
>  			continue;
>  
> -		tdp_mmu_iter_set_spte(kvm, &iter, 0);
> +		tdp_mmu_iter_set_spte(kvm, &iter, SHADOW_NONPRESENT_VALUE);
>  
>  		/*
>  		 * Zappings SPTEs in invalid roots doesn't require a TLB flush,
> -- 
> 2.43.0

I missed one conversion.  Here is the fix.  I found this during reviewing
TDX TDP MMU changes at [1].

[1] https://lore.kernel.org/kvm/20240515005952.3410568-11-rick.p.edgecombe@intel.com/

Paolo, how do you want me to proceed? I can send a updated patch or you can
directly fix the patch in kvm-coco-queue.  I'm fine with either way.


>From 7910130c0a3f2c5d814d6f14d663b4b692a2c7e4 Mon Sep 17 00:00:00 2001
Message-ID: <7910130c0a3f2c5d814d6f14d663b4b692a2c7e4.1715793643.git.isaku.yamahata@...el.com>
From: Isaku Yamahata <isaku.yamahata@...el.com>
Date: Wed, 15 May 2024 10:19:08 -0700
Subject: [PATCH] fixup! KVM: x86/mmu: Replace hardcoded value 0 for the
 initial value for SPTE

---
 arch/x86/kvm/mmu/tdp_mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 1259dd63defc..36539c1b36cd 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -626,7 +626,7 @@ static inline int tdp_mmu_zap_spte_atomic(struct kvm *kvm,
 	 * SPTEs.
 	 */
 	handle_changed_spte(kvm, iter->as_id, iter->gfn, iter->old_spte,
-			    0, iter->level, true);
+			    SHADOW_NONPRESENT_VALUE, iter->level, true);
 
 	return 0;
 }

base-commit: 698ca1e403579ca00e16a5b28ae4d576d9f1b20e
-- 
2.43.2



-- 
Isaku Yamahata <isaku.yamahata@...el.com>