Unlike the primary vCPU-run flow, the nested early checks code doesn't
actually want to propagate VM-Fail back 'vmx'. Yay copy+paste.
In additional to eliminating the need to clear vmx->fail before
returning, using a local boolean also drops a reference to 'vmx' in the
asm blob. Dropping the reference to 'vmx' will save a register in the
long run as future patches will shift all pointer references from 'vmx'
to 'vmx->loaded_vmcs'.
Fixes: 52017608da33 ("KVM: nVMX: add option to perform early consistency checks via H/W")
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/kvm/vmx/nested.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index b92291b8e54b..495edb36b525 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2717,6 +2717,7 @@ static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
unsigned long cr3, cr4;
+ bool vm_fail;
if (!nested_early_check)
return 0;
@@ -2762,14 +2763,18 @@ static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu)
/* Check if vmlaunch or vmresume is needed */
"cmpb $0, %c[launched](%% " _ASM_CX")\n\t"
+ /*
+ * VMLAUNCH and VMRESUME clear RFLAGS.{CF,ZF} on VM-Exit, set
+ * RFLAGS.CF on VM-Fail Invalid and set RFLAGS.ZF on VM-Fail
+ * Valid. vmx_vmenter() directly "returns" RFLAGS, and so the
+ * results of VM-Enter is captured via SETBE to vm_fail.
+ */
"call vmx_vmenter\n\t"
- /* Set vmx->fail accordingly */
- "setbe %c[fail](%% " _ASM_CX")\n\t"
- : ASM_CALL_CONSTRAINT
+ "setbe %%dl\n\t"
+ : ASM_CALL_CONSTRAINT, "=dl"(vm_fail)
: "c"(vmx), "d"((unsigned long)HOST_RSP),
[launched]"i"(offsetof(struct vcpu_vmx, __launched)),
- [fail]"i"(offsetof(struct vcpu_vmx, fail)),
[host_rsp]"i"(offsetof(struct vcpu_vmx, host_rsp)),
[wordsize]"i"(sizeof(ulong))
: "cc", "memory"
@@ -2782,10 +2787,9 @@ static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu)
if (vmx->msr_autoload.guest.nr)
vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, vmx->msr_autoload.guest.nr);
- if (vmx->fail) {
+ if (vm_fail) {
WARN_ON_ONCE(vmcs_read32(VM_INSTRUCTION_ERROR) !=
VMXERR_ENTRY_INVALID_CONTROL_FIELD);
- vmx->fail = 0;
return 1;
}
--
2.20.1
