If we let L1 use EPT, we should probably also support the INVEPT instruction.
In our current nested EPT implementation, when L1 changes its EPT table for
L2 (i.e., EPT12), L0 modifies the shadow EPT table (EPT02), and in the course
of this modification already calls INVEPT. Therefore, when L1 calls INVEPT,
we don't really need to do anything. In particular we *don't* need to call
the real INVEPT again. All we do in our INVEPT is verify the validity of the
call, and its parameters, and then do nothing.
In KVM Forum 2010, Dong et al. presented "Nested Virtualization Friendly KVM"
and classified our current nested EPT implementation as "shadow-like virtual
EPT". He recommended instead a different approach, which he called "VTLB-like
virtual EPT". If we had taken that alternative approach, INVEPT would have had
a bigger role: L0 would only rebuild the shadow EPT table when L1 calls INVEPT.
Signed-off-by: Nadav Har'El <nyh@xxxxxxxxxx>
---
arch/x86/include/asm/vmx.h | 2
arch/x86/kvm/vmx.c | 87 +++++++++++++++++++++++++++++++++++
2 files changed, 89 insertions(+)
--- .before/arch/x86/include/asm/vmx.h 2012-08-01 17:22:47.000000000 +0300
+++ .after/arch/x86/include/asm/vmx.h 2012-08-01 17:22:47.000000000 +0300
@@ -280,6 +280,7 @@ enum vmcs_field {
#define EXIT_REASON_APIC_ACCESS 44
#define EXIT_REASON_EPT_VIOLATION 48
#define EXIT_REASON_EPT_MISCONFIG 49
+#define EXIT_REASON_INVEPT 50
#define EXIT_REASON_WBINVD 54
#define EXIT_REASON_XSETBV 55
#define EXIT_REASON_INVPCID 58
@@ -406,6 +407,7 @@ enum vmcs_field {
#define VMX_EPTP_WB_BIT (1ull << 14)
#define VMX_EPT_2MB_PAGE_BIT (1ull << 16)
#define VMX_EPT_1GB_PAGE_BIT (1ull << 17)
+#define VMX_EPT_INVEPT_BIT (1ull << 20)
#define VMX_EPT_AD_BIT (1ull << 21)
#define VMX_EPT_EXTENT_INDIVIDUAL_BIT (1ull << 24)
#define VMX_EPT_EXTENT_CONTEXT_BIT (1ull << 25)
--- .before/arch/x86/kvm/vmx.c 2012-08-01 17:22:47.000000000 +0300
+++ .after/arch/x86/kvm/vmx.c 2012-08-01 17:22:47.000000000 +0300
@@ -2026,6 +2026,10 @@ static __init void nested_vmx_setup_ctls
/* nested EPT: emulate EPT also to L1 */
nested_vmx_secondary_ctls_high |= SECONDARY_EXEC_ENABLE_EPT;
nested_vmx_ept_caps = VMX_EPT_PAGE_WALK_4_BIT;
+ nested_vmx_ept_caps |=
+ VMX_EPT_INVEPT_BIT | VMX_EPT_EXTENT_GLOBAL_BIT |
+ VMX_EPT_EXTENT_CONTEXT_BIT |
+ VMX_EPT_EXTENT_INDIVIDUAL_BIT;
nested_vmx_ept_caps &= vmx_capability.ept;
} else
nested_vmx_ept_caps = 0;
@@ -5702,6 +5706,87 @@ static int handle_vmptrst(struct kvm_vcp
return 1;
}
+/* Emulate the INVEPT instruction */
+static int handle_invept(struct kvm_vcpu *vcpu)
+{
+ u32 vmx_instruction_info;
+ unsigned long type;
+ gva_t gva;
+ struct x86_exception e;
+ struct {
+ u64 eptp, gpa;
+ } operand;
+
+ if (!(nested_vmx_secondary_ctls_high & SECONDARY_EXEC_ENABLE_EPT) ||
+ !(nested_vmx_ept_caps & VMX_EPT_INVEPT_BIT)) {
+ kvm_queue_exception(vcpu, UD_VECTOR);
+ return 1;
+ }
+
+ if (!nested_vmx_check_permission(vcpu))
+ return 1;
+
+ if (!kvm_read_cr0_bits(vcpu, X86_CR0_PE)) {
+ kvm_queue_exception(vcpu, UD_VECTOR);
+ return 1;
+ }
+
+ /* According to the Intel VMX instruction reference, the memory
+ * operand is read even if it isn't needed (e.g., for type==global)
+ */
+ vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
+ if (get_vmx_mem_address(vcpu, vmcs_readl(EXIT_QUALIFICATION),
+ vmx_instruction_info, &gva))
+ return 1;
+ if (kvm_read_guest_virt(&vcpu->arch.emulate_ctxt, gva, &operand,
+ sizeof(operand), &e)) {
+ kvm_inject_page_fault(vcpu, &e);
+ return 1;
+ }
+
+ type = kvm_register_read(vcpu, (vmx_instruction_info >> 28) & 0xf);
+
+ switch (type) {
+ case VMX_EPT_EXTENT_GLOBAL:
+ if (!(nested_vmx_ept_caps & VMX_EPT_EXTENT_GLOBAL_BIT))
+ nested_vmx_failValid(vcpu,
+ VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
+ else {
+ /*
+ * Do nothing: when L1 changes EPT12, we already
+ * update EPT02 (the shadow EPT table) and call INVEPT.
+ * So when L1 calls INVEPT, there's nothing left to do.
+ */
+ nested_vmx_succeed(vcpu);
+ }
+ break;
+ case VMX_EPT_EXTENT_CONTEXT:
+ if (!(nested_vmx_ept_caps & VMX_EPT_EXTENT_CONTEXT_BIT))
+ nested_vmx_failValid(vcpu,
+ VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
+ else {
+ /* Do nothing */
+ nested_vmx_succeed(vcpu);
+ }
+ break;
+ case VMX_EPT_EXTENT_INDIVIDUAL_ADDR:
+ if (!(nested_vmx_ept_caps & VMX_EPT_EXTENT_INDIVIDUAL_BIT))
+ nested_vmx_failValid(vcpu,
+ VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
+ else {
+ /* Do nothing */
+ nested_vmx_succeed(vcpu);
+ }
+ break;
+ default:
+ nested_vmx_failValid(vcpu,
+ VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
+ }
+
+ skip_emulated_instruction(vcpu);
+ return 1;
+}
+
/*
* The exit handlers return 1 if the exit was handled fully and guest execution
* may resume. Otherwise they set the kvm_run parameter to indicate what needs
@@ -5744,6 +5829,7 @@ static int (*kvm_vmx_exit_handlers[])(st
[EXIT_REASON_PAUSE_INSTRUCTION] = handle_pause,
[EXIT_REASON_MWAIT_INSTRUCTION] = handle_invalid_op,
[EXIT_REASON_MONITOR_INSTRUCTION] = handle_invalid_op,
+ [EXIT_REASON_INVEPT] = handle_invept,
};
static const int kvm_vmx_max_exit_handlers =
@@ -5928,6 +6014,7 @@ static bool nested_vmx_exit_handled(stru
case EXIT_REASON_VMPTRST: case EXIT_REASON_VMREAD:
case EXIT_REASON_VMRESUME: case EXIT_REASON_VMWRITE:
case EXIT_REASON_VMOFF: case EXIT_REASON_VMON:
+ case EXIT_REASON_INVEPT:
/*
* VMX instructions trap unconditionally. This allows L1 to
* emulate them for its L2 guest, i.e., allows 3-level nesting!
--
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