According to section "Checks on Host Segment and Descriptor-Table
Registers" in Intel SDM vol 3C, the following checks are performed on
vmentry of nested guests:
- In the selector field for each of CS, SS, DS, ES, FS, GS and TR, the
RPL (bits 1:0) and the TI flag (bit 2) must be 0.
- The selector fields for CS and TR cannot be 0000H.
- The selector field for SS cannot be 0000H if the "host address-space
size" VM-exit control is 0.
- On processors that support Intel 64 architecture, the base-address
fields for FS, GS, GDTR, IDTR, and TR must contain canonical
addresses.
Signed-off-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
Reviewed-by: Karl Heubaum <karl.heubaum@xxxxxxxxxx>
---
lib/x86/processor.h | 5 ++
x86/vmx_tests.c | 159 ++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 164 insertions(+)
diff --git a/lib/x86/processor.h b/lib/x86/processor.h
index 4fef0bc..8b8bb7a 100644
--- a/lib/x86/processor.h
+++ b/lib/x86/processor.h
@@ -461,6 +461,11 @@ static inline void write_pkru(u32 pkru)
: : "a" (eax), "c" (ecx), "d" (edx));
}
+static inline u64 make_non_canonical(u64 addr)
+{
+ return (addr | 1ull << 48);
+}
+
static inline bool is_canonical(u64 addr)
{
return (s64)(addr << 16) >> 16 == addr;
diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
index b50d858..5911a60 100644
--- a/x86/vmx_tests.c
+++ b/x86/vmx_tests.c
@@ -6938,6 +6938,163 @@ static void test_load_host_pat(void)
test_pat(HOST_PAT, "HOST_PAT", EXI_CONTROLS, EXI_LOAD_PAT);
}
+/*
+ * Test a value for the given VMCS field.
+ *
+ * "field" - VMCS field
+ * "field_name" - string name of VMCS field
+ * "bit_start" - starting bit
+ * "bit_end" - ending bit
+ * "val" - value that the bit range must or must not contain
+ * "valid_val" - whether value given in 'val' must be valid or not
+ * "error" - expected VMCS error when vmentry fails for an invalid value
+ */
+static void test_vmcs_field(u64 field, const char *field_name, u32 bit_start,
+ u32 bit_end, u64 val, bool valid_val, u32 error)
+{
+ u64 field_saved = vmcs_read(field);
+ u32 i;
+ u64 tmp;
+ u32 bit_on;
+ u64 mask = ~0ull;
+
+ mask = (mask >> bit_end) << bit_end;
+ mask = mask | ((1 << bit_start) - 1);
+ tmp = (field_saved & mask) | (val << bit_start);
+
+ vmcs_write(field, tmp);
+ report_prefix_pushf("%s %lx", field_name, tmp);
+ if (valid_val)
+ test_vmx_vmlaunch(0, false);
+ else
+ test_vmx_vmlaunch(error, false);
+ report_prefix_pop();
+
+ for (i = bit_start; i <= bit_end; i = i + 2) {
+ bit_on = ((1ull < i) & (val << bit_start)) ? 0 : 1;
+ if (bit_on)
+ tmp = field_saved | (1ull << i);
+ else
+ tmp = field_saved & ~(1ull << i);
+ vmcs_write(field, tmp);
+ report_prefix_pushf("%s %lx", field_name, tmp);
+ if (valid_val)
+ test_vmx_vmlaunch(error, false);
+ else
+ test_vmx_vmlaunch(0, false);
+ report_prefix_pop();
+ }
+
+ vmcs_write(field, field_saved);
+}
+
+static void test_canonical(u64 field, const char * field_name)
+{
+ u64 addr_saved = vmcs_read(field);
+ u64 addr = addr_saved;
+
+ report_prefix_pushf("%s %lx", field_name, addr);
+ if (is_canonical(addr)) {
+ test_vmx_vmlaunch(0, false);
+ report_prefix_pop();
+
+ addr = make_non_canonical(addr);
+ vmcs_write(field, addr);
+ report_prefix_pushf("%s %lx", field_name, addr);
+ test_vmx_vmlaunch(VMXERR_ENTRY_INVALID_HOST_STATE_FIELD,
+ false);
+
+ vmcs_write(field, addr_saved);
+ } else {
+ test_vmx_vmlaunch(VMXERR_ENTRY_INVALID_HOST_STATE_FIELD,
+ false);
+ }
+ report_prefix_pop();
+}
+
+/*
+ * 1. In the selector field for each of CS, SS, DS, ES, FS, GS and TR, the
+ * RPL (bits 1:0) and the TI flag (bit 2) must be 0.
+ * 2. The selector fields for CS and TR cannot be 0000H.
+ * 3. The selector field for SS cannot be 0000H if the "host address-space
+ * size" VM-exit control is 0.
+ * 4. On processors that support Intel 64 architecture, the base-address
+ * fields for FS, GS and TR must contain canonical addresses.
+ */
+static void test_host_segment_regs(void)
+{
+ u32 exit_ctrl_saved = vmcs_read(EXI_CONTROLS);
+ u16 selector_saved;
+
+ /*
+ * Test RPL and TI flags
+ */
+ test_vmcs_field(HOST_SEL_CS, "HOST_SEL_CS", 0, 2, 0x0, true,
+ VMXERR_ENTRY_INVALID_HOST_STATE_FIELD);
+ test_vmcs_field(HOST_SEL_SS, "HOST_SEL_SS", 0, 2, 0x0, true,
+ VMXERR_ENTRY_INVALID_HOST_STATE_FIELD);
+ test_vmcs_field(HOST_SEL_DS, "HOST_SEL_DS", 0, 2, 0x0, true,
+ VMXERR_ENTRY_INVALID_HOST_STATE_FIELD);
+ test_vmcs_field(HOST_SEL_ES, "HOST_SEL_ES", 0, 2, 0x0, true,
+ VMXERR_ENTRY_INVALID_HOST_STATE_FIELD);
+ test_vmcs_field(HOST_SEL_FS, "HOST_SEL_FS", 0, 2, 0x0, true,
+ VMXERR_ENTRY_INVALID_HOST_STATE_FIELD);
+ test_vmcs_field(HOST_SEL_GS, "HOST_SEL_GS", 0, 2, 0x0, true,
+ VMXERR_ENTRY_INVALID_HOST_STATE_FIELD);
+ test_vmcs_field(HOST_SEL_TR, "HOST_SEL_TR", 0, 2, 0x0, true,
+ VMXERR_ENTRY_INVALID_HOST_STATE_FIELD);
+
+ /*
+ * Test that CS and TR fields can not be 0x0000
+ */
+ test_vmcs_field(HOST_SEL_CS, "HOST_SEL_CS", 3, 15, 0x0000, false,
+ VMXERR_ENTRY_INVALID_HOST_STATE_FIELD);
+ test_vmcs_field(HOST_SEL_TR, "HOST_SEL_TR", 3, 15, 0x0000, false,
+ VMXERR_ENTRY_INVALID_HOST_STATE_FIELD);
+
+ /*
+ * SS field can not be 0x0000 if "host address-space size" VM-exit
+ * control is 0
+ */
+ selector_saved = vmcs_read(HOST_SEL_SS);
+ vmcs_write(HOST_SEL_SS, 0);
+ if (exit_ctrl_saved & EXI_HOST_64) {
+ report_prefix_pushf("HOST_SEL_SS 0");
+ test_vmx_vmlaunch(0, false);
+ report_prefix_pop();
+
+ vmcs_write(EXI_CONTROLS, exit_ctrl_saved & ~EXI_HOST_64);
+ }
+
+ report_prefix_pushf("HOST_SEL_SS 0");
+ test_vmx_vmlaunch(VMXERR_ENTRY_INVALID_HOST_STATE_FIELD, false);
+ report_prefix_pop();
+
+ vmcs_write(HOST_SEL_SS, selector_saved);
+ vmcs_write(EXI_CONTROLS, exit_ctrl_saved);
+
+#ifdef __x86_64__
+ /*
+ * Base address for FS, GS and TR must be canonical
+ */
+ test_canonical(HOST_BASE_FS, "HOST_BASE_FS");
+ test_canonical(HOST_BASE_GS, "HOST_BASE_GS");
+ test_canonical(HOST_BASE_TR, "HOST_BASE_TR");
+#endif
+}
+
+/*
+ * On processors that support Intel 64 architecture, the base-address
+ * fields for GDTR and IDTR must contain canonical addresses.
+ */
+static void test_host_desc_tables(void)
+{
+#ifdef __x86_64__
+ test_canonical(HOST_BASE_GDTR, "HOST_BASE_GDTR");
+ test_canonical(HOST_BASE_IDTR, "HOST_BASE_IDTR");
+#endif
+}
+
/*
* Check that the virtual CPU checks the VMX Host State Area as
* documented in the Intel SDM.
@@ -6958,6 +7115,8 @@ static void vmx_host_state_area_test(void)
test_host_efer();
test_load_host_pat();
+ test_host_segment_regs();
+ test_host_desc_tables();
}
/*
--
2.20.1
