linux-kernel - [PATCH] KVM: x86/mmu: Only allocate shadowed translation cache for sp->role.level <= KVM_MAX_HUGEPAGE

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Date: Wed, 08 May 2024 11:18:42 +0800
From: "Hou Wenlong" <houwenlong.hwl@...group.com>
To: kvm@...r.kernel.org
Cc: "Lai Jiangshan" <jiangshan.ljs@...group.com>,
  "Sean Christopherson" <seanjc@...gle.com>,
  "Paolo Bonzini" <pbonzini@...hat.com>,
  "Thomas Gleixner" <tglx@...utronix.de>,
  "Ingo Molnar" <mingo@...hat.com>,
  "Borislav Petkov" <bp@...en8.de>,
  "Dave Hansen" <dave.hansen@...ux.intel.com>,
   <x86@...nel.org>,
  "H. Peter Anvin" <hpa@...or.com>,
   <linux-kernel@...r.kernel.org>
Subject: [PATCH] KVM: x86/mmu: Only allocate shadowed translation cache for sp->role.level <= KVM_MAX_HUGEPAGE_LEVEL

Only the indirect SP with sp->role.level <= KVM_MAX_HUGEPAGE_LEVEL might
have leaf gptes, so allocation of shadowed translation cache is needed
only for it. Additionally, use sp->shadowed_translation to determine
whether to use the information in shadowed translation cache or not.

Suggested-by: Lai Jiangshan <jiangshan.ljs@...group.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
---
 arch/x86/kvm/mmu/mmu.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index fc3b59b59ee1..8be987d0f05e 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -716,12 +716,12 @@ static bool sp_has_gptes(struct kvm_mmu_page *sp);
 
 static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index)
 {
+	if (sp->shadowed_translation)
+		return sp->shadowed_translation[index] >> PAGE_SHIFT;
+
 	if (sp->role.passthrough)
 		return sp->gfn;
 
-	if (!sp->role.direct)
-		return sp->shadowed_translation[index] >> PAGE_SHIFT;
-
 	return sp->gfn + (index << ((sp->role.level - 1) * SPTE_LEVEL_BITS));
 }
 
@@ -733,7 +733,7 @@ static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index)
  */
 static u32 kvm_mmu_page_get_access(struct kvm_mmu_page *sp, int index)
 {
-	if (sp_has_gptes(sp))
+	if (sp->shadowed_translation)
 		return sp->shadowed_translation[index] & ACC_ALL;
 
 	/*
@@ -754,7 +754,7 @@ static u32 kvm_mmu_page_get_access(struct kvm_mmu_page *sp, int index)
 static void kvm_mmu_page_set_translation(struct kvm_mmu_page *sp, int index,
 					 gfn_t gfn, unsigned int access)
 {
-	if (sp_has_gptes(sp)) {
+	if (sp->shadowed_translation) {
 		sp->shadowed_translation[index] = (gfn << PAGE_SHIFT) | access;
 		return;
 	}
@@ -1697,7 +1697,7 @@ static void kvm_mmu_free_shadow_page(struct kvm_mmu_page *sp)
 	hlist_del(&sp->hash_link);
 	list_del(&sp->link);
 	free_page((unsigned long)sp->spt);
-	if (!sp->role.direct)
+	if (sp->shadowed_translation)
 		free_page((unsigned long)sp->shadowed_translation);
 	kmem_cache_free(mmu_page_header_cache, sp);
 }
@@ -1850,6 +1850,17 @@ static bool kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp,
 static void kvm_mmu_commit_zap_page(struct kvm *kvm,
 				    struct list_head *invalid_list);
 
+static bool sp_might_have_leaf_gptes(struct kvm_mmu_page *sp)
+{
+	if (sp->role.direct)
+		return false;
+
+	if (sp->role.level > KVM_MAX_HUGEPAGE_LEVEL)
+		return false;
+
+	return true;
+}
+
 static bool sp_has_gptes(struct kvm_mmu_page *sp)
 {
 	if (sp->role.direct)
@@ -2199,7 +2210,8 @@ static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm *kvm,
 
 	sp = kvm_mmu_memory_cache_alloc(caches->page_header_cache);
 	sp->spt = kvm_mmu_memory_cache_alloc(caches->shadow_page_cache);
-	if (!role.direct)
+	sp->role = role;
+	if (sp_might_have_leaf_gptes(sp))
 		sp->shadowed_translation = kvm_mmu_memory_cache_alloc(caches->shadowed_info_cache);
 
 	set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
@@ -2216,7 +2228,6 @@ static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm *kvm,
 	kvm_account_mmu_page(kvm, sp);
 
 	sp->gfn = gfn;
-	sp->role = role;
 	hlist_add_head(&sp->hash_link, sp_list);
 	if (sp_has_gptes(sp))
 		account_shadowed(kvm, sp);
-- 
2.31.1