[PATCH v1 2/3] KVM: x86: Handle the case of 5-level shadow page table

Wei Huang
2021-08-05T20:55:39Z

When the 5-level page table CPU flag is exposed, KVM code needs to handle
this case by pointing mmu->root_hpa to a properly-constructed 5-level page
table.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Wei Huang <wei.huang2@amd.com>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/mmu/mmu.c | 46 +++++++++++++++++++++++----------
2 files changed, 34 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 20ddfbac966e..8586ffdf4de8 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -447,6 +447,7 @@ struct kvm_mmu {

u64 *pae_root;
u64 *pml4_root;
+ u64 *pml5_root;

/*
* check zero bits on shadow page table entries, these
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 44e4561e41f5..b162c3e530aa 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3428,7 +3428,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
* the shadow page table may be a PAE or a long mode page table.
*/
pm_mask = PT_PRESENT_MASK | shadow_me_mask;
- if (mmu->shadow_root_level == PT64_ROOT_4LEVEL) {
+ if (mmu->shadow_root_level >= PT64_ROOT_4LEVEL) {
pm_mask |= PT_ACCESSED_MASK | PT_WRITABLE_MASK | PT_USER_MASK;

if (WARN_ON_ONCE(!mmu->pml4_root)) {
@@ -3454,11 +3454,17 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
PT32_ROOT_LEVEL, false);
mmu->pae_root[i] = root | pm_mask;
}
+ mmu->root_hpa = __pa(mmu->pae_root);

- if (mmu->shadow_root_level == PT64_ROOT_4LEVEL)
+ if (mmu->shadow_root_level >= PT64_ROOT_4LEVEL) {
+ mmu->pml4_root[0] = mmu->root_hpa | pm_mask;
mmu->root_hpa = __pa(mmu->pml4_root);
- else
- mmu->root_hpa = __pa(mmu->pae_root);
+ }
+
+ if (mmu->shadow_root_level == PT64_ROOT_5LEVEL) {
+ mmu->pml5_root[0] = mmu->root_hpa | pm_mask;
+ mmu->root_hpa = __pa(mmu->pml5_root);
+ }

set_root_pgd:
mmu->root_pgd = root_pgd;
@@ -3471,7 +3477,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
static int mmu_alloc_special_roots(struct kvm_vcpu *vcpu)
{
struct kvm_mmu *mmu = vcpu->arch.mmu;
- u64 *pml4_root, *pae_root;
+ u64 *pml5_root, *pml4_root, *pae_root;

/*
* When shadowing 32-bit or PAE NPT with 64-bit NPT, the PML4 and PDP
@@ -3487,17 +3493,18 @@ static int mmu_alloc_special_roots(struct kvm_vcpu *vcpu)
* This mess only works with 4-level paging and needs to be updated to
* work with 5-level paging.
*/
- if (WARN_ON_ONCE(mmu->shadow_root_level != PT64_ROOT_4LEVEL))
+ if (WARN_ON_ONCE(mmu->shadow_root_level < PT64_ROOT_4LEVEL)) {
return -EIO;
+ }

- if (mmu->pae_root && mmu->pml4_root)
+ if (mmu->pae_root && mmu->pml4_root && 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))
+ if (WARN_ON_ONCE(!tdp_enabled || mmu->pae_root || mmu->pml4_root || mmu->pml5_root))
return -EIO;

/*
@@ -3506,18 +3513,30 @@ static int mmu_alloc_special_roots(struct kvm_vcpu *vcpu)
*/
pae_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
if (!pae_root)
- return -ENOMEM;
+ goto err_out;

pml4_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
- if (!pml4_root) {
- free_page((unsigned long)pae_root);
- return -ENOMEM;
- }
+ if (!pml4_root)
+ goto err_out;
+
+ pml5_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
+ if (!pml5_root)
+ goto err_out;

mmu->pae_root = pae_root;
mmu->pml4_root = pml4_root;
+ mmu->pml5_root = pml5_root;

return 0;
+err_out:
+ if (pae_root)
+ free_page((unsigned long)pae_root);
+ if (pml4_root)
+ free_page((unsigned long)pml4_root);
+ if (pml5_root)
+ free_page((unsigned long)pml5_root);
+
+ return -ENOMEM;
}

void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu)
@@ -5320,6 +5339,7 @@ static void free_mmu_pages(struct kvm_mmu *mmu)
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 int __kvm_mmu_create(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
--
2.31.1