linux-kernel - [PATCH v10 032/108] KVM: x86/mmu: Make sync_page not use hard-coded 0 as the initial SPTE value

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Message-Id: <adcc3484605cb460a0c00ee5673c83f32a88e6ca.1667110240.git.isaku.yamahata@intel.com>
Date:   Sat, 29 Oct 2022 23:22:33 -0700
From:   isaku.yamahata@...el.com
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>, erdemaktas@...gle.com,
        Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>
Subject: [PATCH v10 032/108] KVM: x86/mmu: Make sync_page not use hard-coded 0 as the initial SPTE value

From: Isaku Yamahata <isaku.yamahata@...el.com>

FNAME(sync_page) in arch/x86/kvm/mmu/paging_tmpl.h assumes that the initial
shadow page table entry (SPTE) is zero.  Remove the assumption by using
SHADOW_NONPRESENT_VALUE that will be updated from 0 to non-zero value.

Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
 arch/x86/kvm/mmu/paging_tmpl.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 5ab5f94dcb6f..6db3f2b5563a 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -1036,7 +1036,8 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
 		gpa_t pte_gpa;
 		gfn_t gfn;
 
-		if (!sp->spt[i])
+		/* spt[i] has initial value of shadow page table allocation */
+		if (sp->spt[i] == SHADOW_NONPRESENT_VALUE)
 			continue;
 
 		pte_gpa = first_pte_gpa + i * sizeof(pt_element_t);
-- 
2.25.1