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

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...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>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2019-01-25 07:41:01 -08:00 committed by Paolo Bonzini
parent 74dfa2784e
commit fbda0fd31a
1 changed files with 3 additions and 3 deletions
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6
arch/x86/kvm/vmx/nested.c
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@ -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)),