linux-kernel - [PATCH 2/7] KVM: selftests: Drop reserved bit checks from PTE accessor

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: <20221006004512.666529-3-seanjc@google.com>
Date:   Thu,  6 Oct 2022 00:45:07 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sean Christopherson <seanjc@...gle.com>
Subject: [PATCH 2/7] KVM: selftests: Drop reserved bit checks from PTE accessor

Drop the reserved bit checks from the helper to retrieve a PTE, there's
very little value in sanity checking the constructed page tables as any
will quickly be noticed in the form of an unexpected #PF.  The checks
also place unnecessary restrictions on the usage of the helpers, e.g. if
a test _wanted_ to set reserved bits for whatever reason.

Removing the NX check in particular allows for the removal of the @vcpu
param, which will in turn allow the helper to be reused nearly verbatim
for addr_gva2gpa().

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 .../selftests/kvm/include/x86_64/processor.h  |  3 +--
 .../selftests/kvm/lib/x86_64/processor.c      | 26 +------------------
 .../kvm/x86_64/emulator_error_test.c          |  2 +-
 3 files changed, 3 insertions(+), 28 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index 30d5df1ebaad..53d52a5ace48 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -827,8 +827,7 @@ static inline uint8_t wrmsr_safe(uint32_t msr, uint64_t val)
 
 bool kvm_is_tdp_enabled(void);
 
-uint64_t *vm_get_page_table_entry(struct kvm_vm *vm, struct kvm_vcpu *vcpu,
-				  uint64_t vaddr);
+uint64_t *vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr);
 
 uint64_t kvm_hypercall(uint64_t nr, uint64_t a0, uint64_t a1, uint64_t a2,
 		       uint64_t a3);
diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index 90b35998b0f3..9e196837a794 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -241,29 +241,11 @@ void virt_map_level(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
 	}
 }
 
-uint64_t *vm_get_page_table_entry(struct kvm_vm *vm, struct kvm_vcpu *vcpu,
-				  uint64_t vaddr)
+uint64_t *vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr)
 {
 	uint16_t index[4];
 	uint64_t *pml4e, *pdpe, *pde;
 	uint64_t *pte;
-	struct kvm_sregs sregs;
-	uint64_t rsvd_mask = 0;
-
-	/* Set the high bits in the reserved mask. */
-	if (vm->pa_bits < 52)
-		rsvd_mask = GENMASK_ULL(51, vm->pa_bits);
-
-	/*
-	 * SDM vol 3, fig 4-11 "Formats of CR3 and Paging-Structure Entries
-	 * with 4-Level Paging and 5-Level Paging".
-	 * If IA32_EFER.NXE = 0 and the P flag of a paging-structure entry is 1,
-	 * the XD flag (bit 63) is reserved.
-	 */
-	vcpu_sregs_get(vcpu, &sregs);
-	if ((sregs.efer & EFER_NX) == 0) {
-		rsvd_mask |= PTE_NX_MASK;
-	}
 
 	TEST_ASSERT(vm->mode == VM_MODE_PXXV48_4K, "Attempt to use "
 		"unknown or unsupported guest mode, mode: 0x%x", vm->mode);
@@ -286,24 +268,18 @@ uint64_t *vm_get_page_table_entry(struct kvm_vm *vm, struct kvm_vcpu *vcpu,
 	pml4e = addr_gpa2hva(vm, vm->pgd);
 	TEST_ASSERT(pml4e[index[3]] & PTE_PRESENT_MASK,
 		"Expected pml4e to be present for gva: 0x%08lx", vaddr);
-	TEST_ASSERT((pml4e[index[3]] & (rsvd_mask | PTE_LARGE_MASK)) == 0,
-		"Unexpected reserved bits set.");
 
 	pdpe = addr_gpa2hva(vm, PTE_GET_PFN(pml4e[index[3]]) * vm->page_size);
 	TEST_ASSERT(pdpe[index[2]] & PTE_PRESENT_MASK,
 		"Expected pdpe to be present for gva: 0x%08lx", vaddr);
 	TEST_ASSERT(!(pdpe[index[2]] & PTE_LARGE_MASK),
 		"Expected pdpe to map a pde not a 1-GByte page.");
-	TEST_ASSERT((pdpe[index[2]] & rsvd_mask) == 0,
-		"Unexpected reserved bits set.");
 
 	pde = addr_gpa2hva(vm, PTE_GET_PFN(pdpe[index[2]]) * vm->page_size);
 	TEST_ASSERT(pde[index[1]] & PTE_PRESENT_MASK,
 		"Expected pde to be present for gva: 0x%08lx", vaddr);
 	TEST_ASSERT(!(pde[index[1]] & PTE_LARGE_MASK),
 		"Expected pde to map a pte not a 2-MByte page.");
-	TEST_ASSERT((pde[index[1]] & rsvd_mask) == 0,
-		"Unexpected reserved bits set.");
 
 	pte = addr_gpa2hva(vm, PTE_GET_PFN(pde[index[1]]) * vm->page_size);
 	TEST_ASSERT(pte[index[0]] & PTE_PRESENT_MASK,
diff --git a/tools/testing/selftests/kvm/x86_64/emulator_error_test.c b/tools/testing/selftests/kvm/x86_64/emulator_error_test.c
index bde247f3c8a1..1abb34735754 100644
--- a/tools/testing/selftests/kvm/x86_64/emulator_error_test.c
+++ b/tools/testing/selftests/kvm/x86_64/emulator_error_test.c
@@ -180,7 +180,7 @@ int main(int argc, char *argv[])
 	hva = addr_gpa2hva(vm, MEM_REGION_GPA);
 	memset(hva, 0, PAGE_SIZE);
 
-	pte = vm_get_page_table_entry(vm, vcpu, MEM_REGION_GVA);
+	pte = vm_get_page_table_entry(vm, MEM_REGION_GVA);
 	*pte |= BIT_ULL(MAXPHYADDR);
 
 	vcpu_run(vcpu);
-- 
2.38.0.rc1.362.ged0d419d3c-goog