[PATCH 2/2] kvm-unit-tests: nSVM: Test that MBZ bits in CR3 and CR4 are not set on vmrun of nested guests

Krish Sadhukhan
2020-05-04T23:16:49Z

According to section "Canonicalization and Consistency Checks" in APM vol. 2,
the following guest state is illegal:

"Any MBZ bit of CR3 is set."
"Any MBZ bit of CR4 is set."

Signed-off-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>

---
x86/svm.h | 6 ++++
x86/svm_tests.c | 105 +++++++++++++++++++++++++++++++++++++++++++++++++-------
2 files changed, 99 insertions(+), 12 deletions(-)

diff --git a/x86/svm.h b/x86/svm.h
index 645deb7..3d5b79c 100644
--- a/x86/svm.h
+++ b/x86/svm.h
@@ -323,6 +323,12 @@ struct __attribute__ ((__packed__)) vmcb {
#define SVM_EXIT_ERR -1

#define SVM_CR0_SELECTIVE_MASK (X86_CR0_TS | X86_CR0_MP)
+#define SVM_CR0_RESERVED_MASK 0xffffffff00000000U
+#define SVM_CR3_LEGACY_RESERVED_MASK 0xfe7U
+#define SVM_CR3_LEGACY_PAE_RESERVED_MASK 0x7U
+#define SVM_CR3_LONG_RESERVED_MASK 0xfff0000000000fe7U
+#define SVM_CR4_LEGACY_RESERVED_MASK 0xffbaf000U
+#define SVM_CR4_RESERVED_MASK 0xffffffffffbaf000U

#define MSR_BITMAP_SIZE 8192

diff --git a/x86/svm_tests.c b/x86/svm_tests.c
index 5a571eb..5d57ad0 100644
--- a/x86/svm_tests.c
+++ b/x86/svm_tests.c
@@ -1596,6 +1596,31 @@ static void basic_guest_main(struct svm_test *test)
{
}

+#define SVM_TEST_CR_RESERVED_BITS(start, end, inc, cr, val, resv_mask) \
+{ \
+ u64 tmp, mask; \
+ int i; \
+ \
+ for (i = start; i <= end; i = i + inc) { \
+ mask = 1ull << i; \
+ if (!(mask & resv_mask)) \
+ continue; \
+ tmp = val | mask; \
+ switch (cr) { \
+ case 0: \
+ vmcb->save.cr0 = tmp; \
+ break; \
+ case 3: \
+ vmcb->save.cr3 = tmp; \
+ break; \
+ case 4: \
+ vmcb->save.cr4 = tmp; \
+ } \
+ report(svm_vmrun() == SVM_EXIT_ERR, "Test CR%d %d:%d: %lx",\
+ cr, end, start, tmp); \
+ } \
+}
+
static void svm_guest_state_test(void)
{
test_set_guest(basic_guest_main);
@@ -1621,32 +1646,88 @@ static void svm_guest_state_test(void)
cr0 |= X86_CR0_CD;
cr0 &= ~X86_CR0_NW;
vmcb->save.cr0 = cr0;
- report (svm_vmrun() == SVM_EXIT_VMMCALL, "CR0: %lx", cr0);
+ report (svm_vmrun() == SVM_EXIT_VMMCALL, "Test CR0 CD=1,NW=0: %lx",
+ cr0);
cr0 |= X86_CR0_NW;
vmcb->save.cr0 = cr0;
- report (svm_vmrun() == SVM_EXIT_VMMCALL, "CR0: %lx", cr0);
+ report (svm_vmrun() == SVM_EXIT_VMMCALL, "Test CR0 CD=1,NW=1: %lx",
+ cr0);
cr0 &= ~X86_CR0_NW;
cr0 &= ~X86_CR0_CD;
vmcb->save.cr0 = cr0;
- report (svm_vmrun() == SVM_EXIT_VMMCALL, "CR0: %lx", cr0);
+ report (svm_vmrun() == SVM_EXIT_VMMCALL, "Test CR0 CD=0,NW=0: %lx",
+ cr0);
cr0 |= X86_CR0_NW;
vmcb->save.cr0 = cr0;
- report (svm_vmrun() == SVM_EXIT_ERR, "CR0: %lx", cr0);
+ report (svm_vmrun() == SVM_EXIT_VMMCALL, "Test CR0 CD=0,NW=1: %lx",
+ cr0);
vmcb->save.cr0 = cr0_saved;

/*
* CR0[63:32] are not zero
*/
- int i;
-
cr0 = cr0_saved;
- for (i = 32; i < 63; i = i + 4) {
- cr0 = cr0_saved | (1ull << i);
- vmcb->save.cr0 = cr0;
- report (svm_vmrun() == SVM_EXIT_ERR, "CR0[63:32]: %lx",
- cr0 >> 32);
- }
+
+ SVM_TEST_CR_RESERVED_BITS(32, 63, 4, 0, cr0_saved,
+ SVM_CR0_RESERVED_MASK);
vmcb->save.cr0 = cr0_saved;
+
+ /*
+ * CR3 MBZ bits based on different modes:
+ * [2:0] - legacy PAE
+ * [2:0], [11:5] - legacy non-PAE
+ * [2:0], [11:5], [63:52] - long mode
+ */
+ u64 cr3_saved = vmcb->save.cr3;
+ u64 cr4_saved = vmcb->save.cr4;
+ u64 cr4 = cr4_saved;
+ efer_saved = vmcb->save.efer;
+ efer = efer_saved;
+
+ efer &= ~EFER_LMA;
+ vmcb->save.efer = efer;
+ cr4 |= X86_CR4_PAE;
+ vmcb->save.cr4 = cr4;
+ SVM_TEST_CR_RESERVED_BITS(0, 2, 1, 3, cr3_saved,
+ SVM_CR3_LEGACY_PAE_RESERVED_MASK);
+
+ cr4 = cr4_saved & ~X86_CR4_PAE;
+ vmcb->save.cr4 = cr4;
+ SVM_TEST_CR_RESERVED_BITS(0, 11, 2, 3, cr3_saved,
+ SVM_CR3_LEGACY_RESERVED_MASK);
+
+ cr4 |= X86_CR4_PAE;
+ vmcb->save.cr4 = cr4;
+ efer |= EFER_LMA;
+ vmcb->save.efer = efer;
+ SVM_TEST_CR_RESERVED_BITS(0, 63, 2, 3, cr3_saved,
+ SVM_CR3_LONG_RESERVED_MASK);
+
+ vmcb->save.cr4 = cr4_saved;
+ vmcb->save.cr3 = cr3_saved;
+ vmcb->save.efer = efer_saved;
+
+ /*
+ * CR4 MBZ bits based on different modes:
+ * [15:12], 17, 19, [31:22] - legacy mode
+ * [15:12], 17, 19, [63:22] - long mode
+ */
+ cr4_saved = vmcb->save.cr4;
+ efer_saved = vmcb->save.efer;
+ efer &= ~EFER_LMA;
+ vmcb->save.efer = efer;
+ SVM_TEST_CR_RESERVED_BITS(12, 31, 2, 4, cr4_saved,
+ SVM_CR4_LEGACY_RESERVED_MASK);
+
+ efer |= EFER_LMA;
+ vmcb->save.efer = efer;
+ SVM_TEST_CR_RESERVED_BITS(12, 31, 2, 4, cr4_saved,
+ SVM_CR4_RESERVED_MASK);
+ SVM_TEST_CR_RESERVED_BITS(32, 63, 4, 4, cr4_saved,
+ SVM_CR4_RESERVED_MASK);
+
+ vmcb->save.cr4 = cr4_saved;
+ vmcb->save.efer = efer_saved;
}

struct svm_test svm_tests[] = {
--
1.8.3.1