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Commit 064aea77 authored by Nadav Har'El's avatar Nadav Har'El Committed by Avi Kivity
Browse files

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: default avatarNadav Har'El <nyh@il.ibm.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent b87a51ae

arch/x86/kvm/vmx.c

+53 −0
Original line number Diff line number Diff line
@@ -4342,6 +4342,59 @@ static int handle_vmoff(struct kvm_vcpu *vcpu) 
	return 1;

}



/*

 * 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

arch/x86/kvm/x86.c

+2 −1
Original line number Diff line number Diff line
@@ -3848,7 +3848,7 @@ static int kvm_fetch_guest_virt(struct x86_emulate_ctxt *ctxt, 
					  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 @@ static int kvm_read_guest_virt(struct x86_emulate_ctxt *ctxt, 
	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,

arch/x86/kvm/x86.h

+4 −0
Original line number Diff line number Diff line
@@ -81,4 +81,8 @@ int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip); 


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