linux-kernel - [PATCH v2] KVM: x86/mmu: Only allocate shadowed translation cache for sp->role.level <= KVM_MAX_HUGEPAGE

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Message-Id: <5b0cda8a7456cda476b14fca36414a56f921dd52.1715398655.git.houwenlong.hwl@antgroup.com>
Date: Sat, 11 May 2024 11:46:37 +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 v2] 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. Then, it can use sp->shadowed_translation to determine
whether to use the information in the shadowed translation cache or not.
Also, extend the WARN in FNAME(sync_spte)() to ensure that this won't
break shadow_mmu_get_sp_for_split().

Suggested-by: Lai Jiangshan <jiangshan.ljs@...group.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
---
v1->v2:
- Remove the order change in kvm_mmu_page_get_gfn() to keep smallest
  diff.
- Drop the helper.
- Extend the WARN in FNAME(sync_spte).

 arch/x86/kvm/mmu/mmu.c         | 11 +++++------
 arch/x86/kvm/mmu/paging_tmpl.h |  2 +-
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index fc3b59b59ee1..dc6f6a272e98 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -719,7 +719,7 @@ static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index)
 	if (sp->role.passthrough)
 		return sp->gfn;

-	if (!sp->role.direct)
+	if (sp->shadowed_translation)
 		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;
 	}
@@ -1697,8 +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)
-		free_page((unsigned long)sp->shadowed_translation);
+	free_page((unsigned long)sp->shadowed_translation);
 	kmem_cache_free(mmu_page_header_cache, sp);
 }

@@ -2199,7 +2198,7 @@ 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)
+	if (!role.direct && role.level <= KVM_MAX_HUGEPAGE_LEVEL)
 		sp->shadowed_translation = kvm_mmu_memory_cache_alloc(caches->shadowed_info_cache);

 	set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 7a87097cb45b..89b5d73e9e3c 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -911,7 +911,7 @@ static int FNAME(sync_spte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, int
 	gpa_t pte_gpa;
 	gfn_t gfn;

-	if (WARN_ON_ONCE(!sp->spt[i]))
+	if (WARN_ON_ONCE(!sp->spt[i] || !sp->shadowed_translation))
 		return 0;

 	first_pte_gpa = FNAME(get_level1_sp_gpa)(sp);
--
2.31.1