[PATCH v3 08/23] KVM: x86/mmu: Link spt to sp during allocation

David Matlack dmatlack at google.com
Fri Apr 1 10:55:39 PDT 2022

Link the shadow page table to the sp (via set_page_private()) during
allocation rather than initialization. This is a more logical place to
do it because allocation time is also where we do the reverse link
(setting sp->spt).

This creates one extra call to set_page_private(), but having multiple
calls to set_page_private() is unavoidable anyway. We either do
set_page_private() during allocation, which requires 1 per allocation
function, or we do it during initialization, which requires 1 per
initialization function.

No functional change intended.

Suggested-by: Ben Gardon <bgardon at google.com>
Signed-off-by: David Matlack <dmatlack at google.com>
 arch/x86/kvm/mmu/tdp_mmu.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index b3b6426725d4..17354e55735f 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -274,6 +274,7 @@ static struct kvm_mmu_page *tdp_mmu_alloc_sp(struct kvm_vcpu *vcpu)
 	sp = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache);
 	sp->spt = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache);
+	set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
 	return sp;
@@ -281,8 +282,6 @@ static struct kvm_mmu_page *tdp_mmu_alloc_sp(struct kvm_vcpu *vcpu)
 static void tdp_mmu_init_sp(struct kvm_mmu_page *sp, tdp_ptep_t sptep,
 			    gfn_t gfn, union kvm_mmu_page_role role)
-	set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
 	sp->role = role;
 	sp->gfn = gfn;
 	sp->ptep = sptep;
@@ -1435,6 +1434,8 @@ static struct kvm_mmu_page *__tdp_mmu_alloc_sp_for_split(gfp_t gfp)
 		return NULL;
+	set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
 	return sp;

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