KVM: selftests: Reuse virt mapping functions for nested EPTs

Rework tdp_map() and friends to use __virt_pg_map() and drop the custom
EPT code in __tdp_pg_map() and tdp_create_pte().  The EPT code and
__virt_pg_map() are practically identical, the main differences are:
  - EPT uses the EPT struct overlay instead of the PTE masks.
  - EPT always assumes 4-level EPTs.

To reuse __virt_pg_map(), extend the PTE masks to work with EPT's RWX and
X-only capabilities, and provide a tdp_mmu_init() API so that EPT can pass
in the EPT PTE masks along with the root page level (which is currently
hardcoded to '4').

Don't reuse KVM's insane overloading of the USER bit for EPT_R as there's
no reason to multiplex bits in the selftests, e.g. selftests aren't trying
to shadow guest PTEs and thus don't care about funnelling protections into
a common permissions check.

Another benefit of reusing the code is having separate handling for
upper-level PTEs vs 4K PTEs, which avoids some quirks like setting the
large bit on a 4K PTE in the EPTs.

For all intents and purposes, no functional change intended.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Link: https://patch.msgid.link/20251230230150.4150236-14-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

2 files changed, 16 insertions, 4 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 05a1fc1780f2..1cf84b8212c6 100644
--- a/tools/testing/selftests/kvm/include/x86/kvm_util_arch.h
+++ b/tools/testing/selftests/kvm/include/x86/kvm_util_arch.h
@@ -14,6 +14,8 @@ struct pte_masks {
 	uint64_t present;
 	uint64_t writable;
 	uint64_t user;
+	uint64_t readable;
+	uint64_t executable;
 	uint64_t accessed;
 	uint64_t dirty;
 	uint64_t huge;
@@ -37,8 +39,6 @@ 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 0164ef090787..e17cbbe71b8f 100644
--- a/tools/testing/selftests/kvm/include/x86/processor.h
+++ b/tools/testing/selftests/kvm/include/x86/processor.h
@@ -1444,6 +1444,8 @@ enum pg_level {
 #define PTE_PRESENT_MASK(mmu)		((mmu)->arch.pte_masks.present)
 #define PTE_WRITABLE_MASK(mmu)		((mmu)->arch.pte_masks.writable)
 #define PTE_USER_MASK(mmu)		((mmu)->arch.pte_masks.user)
+#define PTE_READABLE_MASK(mmu)		((mmu)->arch.pte_masks.readable)
+#define PTE_EXECUTABLE_MASK(mmu)	((mmu)->arch.pte_masks.executable)
 #define PTE_ACCESSED_MASK(mmu)		((mmu)->arch.pte_masks.accessed)
 #define PTE_DIRTY_MASK(mmu)		((mmu)->arch.pte_masks.dirty)
 #define PTE_HUGE_MASK(mmu)		((mmu)->arch.pte_masks.huge)
@@ -1451,13 +1453,23 @@ enum pg_level {
 #define PTE_C_BIT_MASK(mmu)		((mmu)->arch.pte_masks.c)
 #define PTE_S_BIT_MASK(mmu)		((mmu)->arch.pte_masks.s)
 
-#define is_present_pte(mmu, pte)	(!!(*(pte) & PTE_PRESENT_MASK(mmu)))
+/*
+ * For PTEs without a PRESENT bit (i.e. EPT entries), treat the PTE as present
+ * if it's executable or readable, as EPT supports execute-only PTEs, but not
+ * write-only PTEs.
+ */
+#define is_present_pte(mmu, pte)		\
+	(PTE_PRESENT_MASK(mmu) ?		\
+	 !!(*(pte) & PTE_PRESENT_MASK(mmu)) :	\
+	 !!(*(pte) & (PTE_READABLE_MASK(mmu) | PTE_EXECUTABLE_MASK(mmu))))
+#define is_executable_pte(mmu, pte)	\
+	((*(pte) & (PTE_EXECUTABLE_MASK(mmu) | PTE_NX_MASK(mmu))) == PTE_EXECUTABLE_MASK(mmu))
 #define is_writable_pte(mmu, pte)	(!!(*(pte) & PTE_WRITABLE_MASK(mmu)))
 #define is_user_pte(mmu, pte)		(!!(*(pte) & PTE_USER_MASK(mmu)))
 #define is_accessed_pte(mmu, pte)	(!!(*(pte) & PTE_ACCESSED_MASK(mmu)))
 #define is_dirty_pte(mmu, pte)		(!!(*(pte) & PTE_DIRTY_MASK(mmu)))
 #define is_huge_pte(mmu, pte)		(!!(*(pte) & PTE_HUGE_MASK(mmu)))
-#define is_nx_pte(mmu, pte)		(!!(*(pte) & PTE_NX_MASK(mmu)))
+#define is_nx_pte(mmu, pte)		(!is_executable_pte(mmu, pte))
 
 void tdp_mmu_init(struct kvm_vm *vm, int pgtable_levels,
 		  struct pte_masks *pte_masks);