[PATCH V2 7/7] KVM: X86/MMU: Remove mmu_alloc_special_roots()

Lai Jiangshan
2022-05-03T15:08:10Z

From: Lai Jiangshan <jiangshan.ljs@antgroup.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@antgroup.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