UMIP can be emulated almost perfectly on Intel processor by enabling
descriptor-table exits. SMSW does not cause a vmexit and hence it
cannot be changed into a #GP fault, but all in all it's the most
"innocuous" of the unprivileged instructions that UMIP blocks.
In fact, Linux is _also_ emulating SMSW instructions on behalf of the
program that executes them, because some 16-bit programs expect to use
SMSW to detect vm86 mode, so this is an even smaller issue.
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/vmx.c | 29 +++++++++++++++++++++++++++--
1 file changed, 27 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 6c474c94e154..a257ddc644d1 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3651,6 +3651,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
SECONDARY_EXEC_ENABLE_EPT |
SECONDARY_EXEC_UNRESTRICTED_GUEST |
SECONDARY_EXEC_PAUSE_LOOP_EXITING |
+ SECONDARY_EXEC_DESC |
SECONDARY_EXEC_RDTSCP |
SECONDARY_EXEC_ENABLE_INVPCID |
SECONDARY_EXEC_APIC_REGISTER_VIRT |
@@ -4347,6 +4348,14 @@ static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
(to_vmx(vcpu)->rmode.vm86_active ?
KVM_RMODE_VM_CR4_ALWAYS_ON : KVM_PMODE_VM_CR4_ALWAYS_ON);
+ if ((cr4 & X86_CR4_UMIP) && !boot_cpu_has(X86_FEATURE_UMIP)) {
+ vmcs_set_bits(SECONDARY_VM_EXEC_CONTROL,
+ SECONDARY_EXEC_DESC);
+ hw_cr4 &= ~X86_CR4_UMIP;
+ } else
+ vmcs_clear_bits(SECONDARY_VM_EXEC_CONTROL,
+ SECONDARY_EXEC_DESC);
+
if (cr4 & X86_CR4_VMXE) {
/*
* To use VMXON (and later other VMX instructions), a guest
@@ -5296,6 +5305,7 @@ static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx)
struct kvm_vcpu *vcpu = &vmx->vcpu;
u32 exec_control = vmcs_config.cpu_based_2nd_exec_ctrl;
+
if (!cpu_need_virtualize_apic_accesses(vcpu))
exec_control &= ~SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
if (vmx->vpid == 0)
@@ -5314,6 +5324,11 @@ static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx)
exec_control &= ~(SECONDARY_EXEC_APIC_REGISTER_VIRT |
SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY);
exec_control &= ~SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE;
+
+ /* SECONDARY_EXEC_DESC is enabled/disabled on writes to CR4.UMIP,
+ * in vmx_set_cr4. */
+ exec_control &= ~SECONDARY_EXEC_DESC;
+
/* SECONDARY_EXEC_SHADOW_VMCS is enabled when L1 executes VMPTRLD
(handle_vmptrld).
We can NOT enable shadow_vmcs here because we don't have yet
@@ -6064,6 +6079,12 @@ static int handle_set_cr4(struct kvm_vcpu *vcpu, unsigned long val)
return kvm_set_cr4(vcpu, val);
}
+static int handle_desc(struct kvm_vcpu *vcpu)
+{
+ WARN_ON(!(vcpu->arch.cr4 & X86_CR4_UMIP));
+ return emulate_instruction(vcpu, 0) == EMULATE_DONE;
+}
+
static int handle_cr(struct kvm_vcpu *vcpu)
{
unsigned long exit_qualification, val;
@@ -8152,6 +8173,8 @@ static int (*const kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
[EXIT_REASON_XSETBV] = handle_xsetbv,
[EXIT_REASON_TASK_SWITCH] = handle_task_switch,
[EXIT_REASON_MCE_DURING_VMENTRY] = handle_machine_check,
+ [EXIT_REASON_GDTR_IDTR] = handle_desc,
+ [EXIT_REASON_LDTR_TR] = handle_desc,
[EXIT_REASON_EPT_VIOLATION] = handle_ept_violation,
[EXIT_REASON_EPT_MISCONFIG] = handle_ept_misconfig,
[EXIT_REASON_PAUSE_INSTRUCTION] = handle_pause,
@@ -9097,7 +9120,8 @@ static bool vmx_xsaves_supported(void)
static bool vmx_umip_emulated(void)
{
- return false;
+ return vmcs_config.cpu_based_2nd_exec_ctrl &
+ SECONDARY_EXEC_DESC;
}
static void vmx_recover_nmi_blocking(struct vcpu_vmx *vmx)
@@ -9691,7 +9715,8 @@ static void vmcs_set_secondary_exec_control(u32 new_ctl)
u32 mask =
SECONDARY_EXEC_SHADOW_VMCS |
SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE |
- SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
+ SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
+ SECONDARY_EXEC_DESC;
u32 cur_ctl = vmcs_read32(SECONDARY_VM_EXEC_CONTROL);
--
1.8.3.1
