...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@xxxxxxxxx>
---
arch/x86/kvm/vmx/nested.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 6e53e50cad86..ba2434540fc4 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)),
--
2.20.1
