.to verify KVM performs the appropriate consistency checks for loading
IA32_PAT as part of running a nested guest.
According to section "Checks on Host Control Registers and MSRs" in Intel
SDM vol 3C, the following check is performed on vmentry:
If the “load IA32_PAT” VM-exit control is 1, the value of the field
for the IA32_PAT MSR must be one that could be written by WRMSR
without fault at CPL 0. Specifically, each of the 8 bytes in the
field must have one of the values 0 (UC), 1 (WC), 4 (WT), 5 (WP),
6 (WB), or 7 (UC-).
Since a PAT value higher than 8 will yield the same test result as that
of 8, we want to confine our tests only up to 8 in order to reduce
redundancy of tests and to avoid too many vmentries.
Signed-off-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
Reviewed-by: Karl Heubaum <karl.heubaum@xxxxxxxxxx>
Reviewed-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
x86/vmx_tests.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 72 insertions(+)
diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
index 66a87f6..380fd85 100644
--- a/x86/vmx_tests.c
+++ b/x86/vmx_tests.c
@@ -4995,6 +4995,76 @@ static void test_sysenter_field(u32 field, const char *name)
vmcs_write(field, addr_saved);
}
+/*
+ * PAT values higher than 8 are uninteresting since they're likely lumped
+ * in with "8". We cap the tests at PAT value of 8 in order to reduce the
+ * number of VM-Entries and keep the runtime reasonable.
+ */
+#define PAT_VAL_LIMIT 8
+
+static void test_pat(u32 field, const char * field_name, u32 ctrl_field,
+ u64 ctrl_bit)
+{
+ u32 ctrl_saved = vmcs_read(ctrl_field);
+ u64 pat_saved = vmcs_read(field);
+ u64 i, val;
+ u32 j;
+ int error;
+
+ vmcs_write(ctrl_field, ctrl_saved & ~ctrl_bit);
+ for (i = 0; i <= PAT_VAL_LIMIT; i++) {
+ /* Test PAT0..PAT7 fields */
+ for (j = 0; j < 8; j++) {
+ val = i << j * 8;
+ vmcs_write(field, val);
+ report_prefix_pushf("%s %lx", field_name, val);
+ test_vmx_vmlaunch(0, false);
+ report_prefix_pop();
+ }
+ }
+
+ vmcs_write(ctrl_field, ctrl_saved | ctrl_bit);
+ for (i = 0; i <= PAT_VAL_LIMIT; i++) {
+ /* Test PAT0..PAT7 fields */
+ for (j = 0; j < 8; j++) {
+ val = i << j * 8;
+ vmcs_write(field, val);
+ report_prefix_pushf("%s %lx", field_name, val);
+ if (i == 0x2 || i == 0x3 || i >= 0x8)
+ error = VMXERR_ENTRY_INVALID_HOST_STATE_FIELD;
+ else
+ error = 0;
+ test_vmx_vmlaunch(error, false);
+ report_prefix_pop();
+ }
+ }
+
+ vmcs_write(ctrl_field, ctrl_saved);
+ vmcs_write(field, pat_saved);
+}
+
+/*
+ * If the "load IA32_PAT" VM-exit control is 1, the value of the field
+ * for the IA32_PAT MSR must be one that could be written by WRMSR
+ * without fault at CPL 0. Specifically, each of the 8 bytes in the
+ * field must have one of the values 0 (UC), 1 (WC), 4 (WT), 5 (WP),
+ * 6 (WB), or 7 (UC-).
+ *
+ * [Intel SDM]
+ */
+static void test_load_host_pat(void)
+{
+ /*
+ * "load IA32_PAT" VM-exit control
+ */
+ if (!(ctrl_exit_rev.clr & EXI_LOAD_PAT)) {
+ printf("\"Load-IA32-PAT\" exit control not supported\n");
+ return;
+ }
+
+ test_pat(HOST_PAT, "HOST_PAT", EXI_CONTROLS, EXI_LOAD_PAT);
+}
+
/*
* Check that the virtual CPU checks the VMX Host State Area as
* documented in the Intel SDM.
@@ -5010,6 +5080,8 @@ static void vmx_host_state_area_test(void)
test_sysenter_field(HOST_SYSENTER_ESP, "HOST_SYSENTER_ESP");
test_sysenter_field(HOST_SYSENTER_EIP, "HOST_SYSENTER_EIP");
+
+ test_load_host_pat();
}
static bool valid_vmcs_for_vmentry(void)
--
2.17.2
