linux-kernel - [PATCH 2/4] KVM: selftests: Use a loop to walk guest page tables

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250917215031.2567566-3-jmattson@google.com>
Date: Wed, 17 Sep 2025 14:48:38 -0700
From: Jim Mattson <jmattson@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Shuah Khan <shuah@...nel.org>, 
	Sean Christopherson <seanjc@...gle.com>, Bibo Mao <maobibo@...ngson.cn>, 
	Huacai Chen <chenhuacai@...nel.org>, Andrew Jones <ajones@...tanamicro.com>, 
	Claudio Imbrenda <imbrenda@...ux.ibm.com>, "Pratik R. Sampat" <prsampat@....com>, 
	Kai Huang <kai.huang@...el.com>, Eric Auger <eric.auger@...hat.com>, 
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	linux-kselftest@...r.kernel.org
Cc: Jim Mattson <jmattson@...gle.com>
Subject: [PATCH 2/4] KVM: selftests: Use a loop to walk guest page tables

Walk the guest page tables via a loop when searching for a PTE,
instead of using unique variables for each level of the page tables.

This simplifies the code and makes it easier to support 5-level paging
in the future.

Signed-off-by: Jim Mattson <jmattson@...gle.com>
---
 .../testing/selftests/kvm/lib/x86/processor.c | 21 +++++++------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
index 0238e674709d..433365c8196d 100644
--- a/tools/testing/selftests/kvm/lib/x86/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86/processor.c
@@ -270,7 +270,8 @@ static bool vm_is_target_pte(uint64_t *pte, int *level, int current_level)
 uint64_t *__vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr,
 				    int *level)
 {
-	uint64_t *pml4e, *pdpe, *pde;
+	uint64_t *pte = &vm->pgd;
+	int current_level;
 
 	TEST_ASSERT(!vm->arch.is_pt_protected,
 		    "Walking page tables of protected guests is impossible");
@@ -291,19 +292,13 @@ uint64_t *__vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr,
 	TEST_ASSERT(vaddr == (((int64_t)vaddr << 16) >> 16),
 		"Canonical check failed.  The virtual address is invalid.");
 
-	pml4e = virt_get_pte(vm, &vm->pgd, vaddr, PG_LEVEL_512G);
-	if (vm_is_target_pte(pml4e, level, PG_LEVEL_512G))
-		return pml4e;
-
-	pdpe = virt_get_pte(vm, pml4e, vaddr, PG_LEVEL_1G);
-	if (vm_is_target_pte(pdpe, level, PG_LEVEL_1G))
-		return pdpe;
-
-	pde = virt_get_pte(vm, pdpe, vaddr, PG_LEVEL_2M);
-	if (vm_is_target_pte(pde, level, PG_LEVEL_2M))
-		return pde;
+	for (current_level = vm->pgtable_levels; current_level > 0; current_level--) {
+		pte = virt_get_pte(vm, pte, vaddr, current_level);
+		if (vm_is_target_pte(pte, level, current_level))
+			return pte;
+	}
 
-	return virt_get_pte(vm, pde, vaddr, PG_LEVEL_4K);
+	return pte;
 }
 
 uint64_t *vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr)
-- 
2.51.0.470.ga7dc726c21-goog