KVM: nVMX: Decoding memory operands of VMX instructions
This patch includes a utility function for decoding pointer operands of VMX
instructions issued by L1 (a guest hypervisor)
Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 487952b..74afd86 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4343,6 +4343,59 @@
}
/*
+ * Decode the memory-address operand of a vmx instruction, as recorded on an
+ * exit caused by such an instruction (run by a guest hypervisor).
+ * On success, returns 0. When the operand is invalid, returns 1 and throws
+ * #UD or #GP.
+ */
+static int get_vmx_mem_address(struct kvm_vcpu *vcpu,
+ unsigned long exit_qualification,
+ u32 vmx_instruction_info, gva_t *ret)
+{
+ /*
+ * According to Vol. 3B, "Information for VM Exits Due to Instruction
+ * Execution", on an exit, vmx_instruction_info holds most of the
+ * addressing components of the operand. Only the displacement part
+ * is put in exit_qualification (see 3B, "Basic VM-Exit Information").
+ * For how an actual address is calculated from all these components,
+ * refer to Vol. 1, "Operand Addressing".
+ */
+ int scaling = vmx_instruction_info & 3;
+ int addr_size = (vmx_instruction_info >> 7) & 7;
+ bool is_reg = vmx_instruction_info & (1u << 10);
+ int seg_reg = (vmx_instruction_info >> 15) & 7;
+ int index_reg = (vmx_instruction_info >> 18) & 0xf;
+ bool index_is_valid = !(vmx_instruction_info & (1u << 22));
+ int base_reg = (vmx_instruction_info >> 23) & 0xf;
+ bool base_is_valid = !(vmx_instruction_info & (1u << 27));
+
+ if (is_reg) {
+ kvm_queue_exception(vcpu, UD_VECTOR);
+ return 1;
+ }
+
+ /* Addr = segment_base + offset */
+ /* offset = base + [index * scale] + displacement */
+ *ret = vmx_get_segment_base(vcpu, seg_reg);
+ if (base_is_valid)
+ *ret += kvm_register_read(vcpu, base_reg);
+ if (index_is_valid)
+ *ret += kvm_register_read(vcpu, index_reg)<<scaling;
+ *ret += exit_qualification; /* holds the displacement */
+
+ if (addr_size == 1) /* 32 bit */
+ *ret &= 0xffffffff;
+
+ /*
+ * TODO: throw #GP (and return 1) in various cases that the VM*
+ * instructions require it - e.g., offset beyond segment limit,
+ * unusable or unreadable/unwritable segment, non-canonical 64-bit
+ * address, and so on. Currently these are not checked.
+ */
+ return 0;
+}
+
+/*
* 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
* to be done to userspace and return 0.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 460932b..27d12a3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3848,7 +3848,7 @@
exception);
}
-static int kvm_read_guest_virt(struct x86_emulate_ctxt *ctxt,
+int kvm_read_guest_virt(struct x86_emulate_ctxt *ctxt,
gva_t addr, void *val, unsigned int bytes,
struct x86_exception *exception)
{
@@ -3858,6 +3858,7 @@
return kvm_read_guest_virt_helper(addr, val, bytes, vcpu, access,
exception);
}
+EXPORT_SYMBOL_GPL(kvm_read_guest_virt);
static int kvm_read_guest_virt_system(struct x86_emulate_ctxt *ctxt,
gva_t addr, void *val, unsigned int bytes,
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index e407ed3..6f15053 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -81,4 +81,8 @@
void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data);
+int kvm_read_guest_virt(struct x86_emulate_ctxt *ctxt,
+ gva_t addr, void *val, unsigned int bytes,
+ struct x86_exception *exception);
+
#endif