[PATCH v2 3/6] KVM: nVMX: Do a bitwise-AND of regs_avail when switching active VMCS

Sean Christopherson
2026-04-09T22:42:53Z

When switching between vmcs01 and vmcs02, do a bitwise-AND of regs_avail
to effectively reset the mask for the new VMCS, purely to be consistent
with all other "full" writes of regs_avail. In practice, a straight write
versus a bitwise-AND will yield the same result, as kvm_arch_vcpu_create()
marks *all* registers available (and dirty), and KVM never marks registers
unavailable unless they're lazily loaded.

This will allow adding wrapper APIs to set regs_{avail,dirty} without
having to add special handling for a nVMX use case that doesn't exist in
practice.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/vmx/nested.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 22b1f06a9d40..63c4ca8c97d5 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -310,7 +310,7 @@ static void vmx_switch_vmcs(struct kvm_vcpu *vcpu, struct loaded_vmcs *vmcs)
vmx_sync_vmcs_host_state(vmx, prev);
put_cpu();

- vcpu->arch.regs_avail = ~VMX_REGS_LAZY_LOAD_SET;
+ vcpu->arch.regs_avail &= ~VMX_REGS_LAZY_LOAD_SET;

/*
* All lazily updated registers will be reloaded from VMCS12 on both
--
2.53.0.1213.gd9a14994de-goog