Commit fbda0fd3 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: nVMX: Let the compiler select the reg for holding HOST_RSP 



...and provide an explicit name for the constraint.  Naming the input
constraint makes the code self-documenting and also avoids the fragility
of numerically referring to constraints, e.g. %4 breaks badly whenever
the constraints are modified.

Explicitly using RDX was inherited from vCPU-run, i.e. completely
arbitrary.  Even vCPU-run doesn't truly need to explicitly use RDX, but
doing so is more robust as vCPU-run needs tight control over its
register usage.

Note that while the naming "conflict" between host_rsp and HOST_RSP
is slightly confusing, the former will be renamed slightly in a
future patch, at which point HOST_RSP is absolutely what is desired.

Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: default avatarJim Mattson <jmattson@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 74dfa278

arch/x86/kvm/vmx/nested.c

+3 −3
Original line number Diff line number Diff line
@@ -2753,9 +2753,8 @@ static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu) 
	}



	asm(

		/* Set HOST_RSP */

		"sub $%c[wordsize], %%" _ASM_SP "\n\t" /* temporarily adjust RSP for CALL */

		__ex("vmwrite %%" _ASM_SP ", %%" _ASM_DX) "\n\t"

		__ex("vmwrite %%" _ASM_SP ", %[HOST_RSP]") "\n\t"

		"mov %%" _ASM_SP ", %c[host_rsp](%% " _ASM_CX ")\n\t"

		"add $%c[wordsize], %%" _ASM_SP "\n\t" /* un-adjust RSP */
@@ -2772,7 +2771,8 @@ static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu) 


		CC_SET(be)

	      : ASM_CALL_CONSTRAINT, CC_OUT(be) (vm_fail)

	      : "c"(vmx), "d"((unsigned long)HOST_RSP),

	      : "c"(vmx),

		[HOST_RSP]"r"((unsigned long)HOST_RSP),

		[loaded_vmcs]"r"(vmx->loaded_vmcs),

		[launched]"i"(offsetof(struct loaded_vmcs, launched)),

		[host_rsp]"i"(offsetof(struct vcpu_vmx, host_rsp)),