linux-kernel - [PATCH V2 7/7] KVM: X86/MMU: Remove mmu_alloc_special

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Message-Id: <20220503150735.32723-8-jiangshanlai@gmail.com>
Date:   Tue,  3 May 2022 23:07:35 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Lai Jiangshan <jiangshan.ljs@...group.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        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>
Subject: [PATCH V2 7/7] KVM: X86/MMU: Remove mmu_alloc_special_roots()

From: Lai Jiangshan <jiangshan.ljs@...group.com>

mmu_alloc_special_roots() allocates mmu->pae_root for non-PAE paging
(as for shadowing 32bit NPT on 64 bit host) and mmu->pml4_root and
mmu->pml5_root.

But mmu->pml4_root and mmu->pml5_root is not used, neither mmu->pae_root
for non-PAE paging.

So remove mmu_alloc_special_roots(), mmu->pml4_root and mmu->pml5_root.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@...group.com>
---
 arch/x86/include/asm/kvm_host.h |  3 --
 arch/x86/kvm/mmu/mmu.c          | 77 ---------------------------------
 2 files changed, 80 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c59fea4bdb6e..e647587d1d1f 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -458,9 +458,6 @@ struct kvm_mmu {
 	u8 permissions[16];
 
 	u64 *pae_root;
-	u64 *pml4_root;
-	u64 *pml5_root;
-
 	/*
 	 * check zero bits on shadow page table entries, these
 	 * bits include not only hardware reserved bits but also
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index c97f830c5f8c..9c04acf9728a 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3611,78 +3611,6 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 	return r;
 }
 
-static int mmu_alloc_special_roots(struct kvm_vcpu *vcpu)
-{
-	struct kvm_mmu *mmu = vcpu->arch.mmu;
-	bool need_pml5 = mmu->root_role.level > PT64_ROOT_4LEVEL;
-	u64 *pml5_root = NULL;
-	u64 *pml4_root = NULL;
-	u64 *pae_root;
-
-	/*
-	 * When shadowing 32-bit or PAE NPT with 64-bit NPT, the PML4 and PDP
-	 * tables are allocated and initialized at root creation as there is no
-	 * equivalent level in the guest's NPT to shadow.  Allocate the tables
-	 * on demand, as running a 32-bit L1 VMM on 64-bit KVM is very rare.
-	 */
-	if (mmu->root_role.direct ||
-	    mmu->cpu_role.base.level >= PT64_ROOT_4LEVEL ||
-	    mmu->root_role.level < PT64_ROOT_4LEVEL)
-		return 0;
-
-	/*
-	 * NPT, the only paging mode that uses this horror, uses a fixed number
-	 * of levels for the shadow page tables, e.g. all MMUs are 4-level or
-	 * all MMus are 5-level.  Thus, this can safely require that pml5_root
-	 * is allocated if the other roots are valid and pml5 is needed, as any
-	 * prior MMU would also have required pml5.
-	 */
-	if (mmu->pae_root && mmu->pml4_root && (!need_pml5 || mmu->pml5_root))
-		return 0;
-
-	/*
-	 * The special roots should always be allocated in concert.  Yell and
-	 * bail if KVM ends up in a state where only one of the roots is valid.
-	 */
-	if (WARN_ON_ONCE(!tdp_enabled || mmu->pae_root || mmu->pml4_root ||
-			 (need_pml5 && mmu->pml5_root)))
-		return -EIO;
-
-	/*
-	 * Unlike 32-bit NPT, the PDP table doesn't need to be in low mem, and
-	 * doesn't need to be decrypted.
-	 */
-	pae_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
-	if (!pae_root)
-		return -ENOMEM;
-
-#ifdef CONFIG_X86_64
-	pml4_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
-	if (!pml4_root)
-		goto err_pml4;
-
-	if (need_pml5) {
-		pml5_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
-		if (!pml5_root)
-			goto err_pml5;
-	}
-#endif
-
-	mmu->pae_root = pae_root;
-	mmu->pml4_root = pml4_root;
-	mmu->pml5_root = pml5_root;
-
-	return 0;
-
-#ifdef CONFIG_X86_64
-err_pml5:
-	free_page((unsigned long)pml4_root);
-err_pml4:
-	free_page((unsigned long)pae_root);
-	return -ENOMEM;
-#endif
-}
-
 static bool is_unsync_root(hpa_t root)
 {
 	struct kvm_mmu_page *sp;
@@ -5069,9 +4997,6 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
 	r = mmu_alloc_pae_root(vcpu);
 	if (r)
 		return r;
-	r = mmu_alloc_special_roots(vcpu);
-	if (r)
-		goto out;
 	if (vcpu->arch.mmu->root_role.direct)
 		r = mmu_alloc_direct_roots(vcpu);
 	else
@@ -5529,8 +5454,6 @@ static void free_mmu_pages(struct kvm_mmu *mmu)
 	if (!tdp_enabled && mmu->pae_root)
 		set_memory_encrypted((unsigned long)mmu->pae_root, 1);
 	free_page((unsigned long)mmu->pae_root);
-	free_page((unsigned long)mmu->pml4_root);
-	free_page((unsigned long)mmu->pml5_root);
 }
 
 static void __kvm_mmu_create(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
-- 
2.19.1.6.gb485710b