KVM: selftests: Use a TDP MMU to share EPT page tables between vCPUs

prepare_eptp() currently allocates new EPTs for each vCPU.  memstress has
its own hack to share the EPTs between vCPUs.  Currently, there is no
reason to have separate EPTs for each vCPU, and the complexity is
significant.  The only reason it doesn't matter now is because memstress
is the only user with multiple vCPUs.

Add vm_enable_ept() to allocate EPT page tables for an entire VM, and use
it everywhere to replace prepare_eptp().  Drop 'eptp' and 'eptp_hva' from
'struct vmx_pages' as they serve no purpose (e.g. the EPTP can be built
from the PGD), but keep 'eptp_gpa' so that the MMU structure doesn't need
to be passed in along with vmx_pages.  Dynamically allocate the TDP MMU
structure to avoid a cyclical dependency between kvm_util_arch.h and
kvm_util.h.

Remove the workaround in memstress to copy the EPT root between vCPUs
since that's now the default behavior.

Name the MMU tdp_mmu instead of e.g. nested_mmu or nested.mmu to avoid
recreating the same mess that KVM has with respect to "nested" MMUs, e.g.
does nested refer to the stage-2 page tables created by L1, or the stage-1
page tables created by L2?

Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Link: https://patch.msgid.link/20251230230150.4150236-11-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

3 files changed, 10 insertions, 5 deletions

diff --git a/tools/testing/selftests/kvm/include/x86/kvm_util_arch.h b/tools/testing/selftests/kvm/include/x86/kvm_util_arch.h
index bad381d63b6a..05a1fc1780f2 100644
--- a/tools/testing/selftests/kvm/include/x86/kvm_util_arch.h
+++ b/tools/testing/selftests/kvm/include/x86/kvm_util_arch.h
@@ -26,6 +26,8 @@ struct kvm_mmu_arch {
 	struct pte_masks pte_masks;
 };
 
+struct kvm_mmu;
+
 struct kvm_vm_arch {
 	vm_vaddr_t gdt;
 	vm_vaddr_t tss;
@@ -35,6 +37,8 @@ struct kvm_vm_arch {
 	uint64_t s_bit;
 	int sev_fd;
 	bool is_pt_protected;
+
+	struct kvm_mmu *tdp_mmu;
 };
 
 static inline bool __vm_arch_has_protected_memory(struct kvm_vm_arch *arch)
diff --git a/tools/testing/selftests/kvm/include/x86/processor.h b/tools/testing/selftests/kvm/include/x86/processor.h
index 55dac84cd4a7..0164ef090787 100644
--- a/tools/testing/selftests/kvm/include/x86/processor.h
+++ b/tools/testing/selftests/kvm/include/x86/processor.h
@@ -1459,6 +1459,9 @@ enum pg_level {
 #define is_huge_pte(mmu, pte)		(!!(*(pte) & PTE_HUGE_MASK(mmu)))
 #define is_nx_pte(mmu, pte)		(!!(*(pte) & PTE_NX_MASK(mmu)))
 
+void tdp_mmu_init(struct kvm_vm *vm, int pgtable_levels,
+		  struct pte_masks *pte_masks);
+
 void __virt_pg_map(struct kvm_vm *vm, struct kvm_mmu *mmu, uint64_t vaddr,
 		   uint64_t paddr,  int level);
 void virt_map_level(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
diff --git a/tools/testing/selftests/kvm/include/x86/vmx.h b/tools/testing/selftests/kvm/include/x86/vmx.h
index 04b8231d032a..1fd83c23529a 100644
--- a/tools/testing/selftests/kvm/include/x86/vmx.h
+++ b/tools/testing/selftests/kvm/include/x86/vmx.h
@@ -520,13 +520,11 @@ struct vmx_pages {
 	uint64_t vmwrite_gpa;
 	void *vmwrite;
 
-	void *eptp_hva;
-	uint64_t eptp_gpa;
-	void *eptp;
-
 	void *apic_access_hva;
 	uint64_t apic_access_gpa;
 	void *apic_access;
+
+	uint64_t eptp_gpa;
 };
 
 union vmx_basic {
@@ -568,7 +566,7 @@ void tdp_identity_map_default_memslots(struct vmx_pages *vmx,
 void tdp_identity_map_1g(struct vmx_pages *vmx, struct kvm_vm *vm,
 			 uint64_t addr, uint64_t size);
 bool kvm_cpu_has_ept(void);
-void prepare_eptp(struct vmx_pages *vmx, struct kvm_vm *vm);
+void vm_enable_ept(struct kvm_vm *vm);
 void prepare_virtualize_apic_accesses(struct vmx_pages *vmx, struct kvm_vm *vm);
 
 #endif /* SELFTEST_KVM_VMX_H */