| Message ID | 20190125154120.19385-15-sean.j.christopherson@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: VMX: Move vCPU-run to proper asm sub-routine | expand |
On Fri, Jan 25, 2019 at 7:42 AM Sean Christopherson <sean.j.christopherson@intel.com> wrote: > > ...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: Sean Christopherson <sean.j.christopherson@intel.com> Reviewed-by: Jim Mattson <jmattson@google.com>
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index d42134f836a6..48281b0684ca 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -2752,9 +2752,8 @@ 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 */ @@ -2771,7 +2770,8 @@ 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)),
...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: Sean Christopherson <sean.j.christopherson@intel.com> --- arch/x86/kvm/vmx/nested.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)