KVM: nSVM: Use intuitive local variables in nested_vmcb02_recalc_intercepts()

Now that nested_vmcb02_recalc_intercepts() is explicitly scoped to deal
with *only* recalculating vmcb02 intercepts, rename its local variables to
use more intuivite names.  The current "c", "h", and "g" local variables,
for the current VMCB, vmcb01, and (cached) vmcb12 respectively, are short
and sweet, but don't do much to help unfamiliar readers understand what
the code is doing.

Use vmcb12_ctrl/vmcb01/vmcb02/vmcb12_ctrl in lieu of c/h/g to make it clear
the function is updating intercepts in vmcb02 based on the intercepts in
vmcb01 and (cached) vmcb12.

Opportunistically change the existing WARN_ON to a WARN_ON_ONCE so that a
KVM bug doesn't unintentionally DoS the host.

No functional change intended.

Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
[sean: use WARN_ON_ONCE, keep local vmcb12 cache as vmcb12_ctrl]
Link: https://patch.msgid.link/20260218230958.2877682-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 5ee77a5130d361fcd27010ffae4bfae9bd2266c0..46804b54200d23016ef4c044e1c19ff1ee896e6b 100644 (file)
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -124,23 +124,20 @@ static bool nested_vmcb_needs_vls_intercept(struct vcpu_svm *svm)
 
 void nested_vmcb02_recalc_intercepts(struct vcpu_svm *svm)
 {
-       struct vmcb_control_area *c, *h;
-       struct vmcb_ctrl_area_cached *g;
+       struct vmcb_ctrl_area_cached *vmcb12_ctrl = &svm->nested.ctl;
+       struct vmcb *vmcb02 = svm->nested.vmcb02.ptr;
+       struct vmcb *vmcb01 = svm->vmcb01.ptr;
        unsigned int i;
 
-       if (WARN_ON_ONCE(svm->vmcb != svm->nested.vmcb02.ptr))
+       if (WARN_ON_ONCE(svm->vmcb != vmcb02))
                return;
 
-       vmcb_mark_dirty(svm->vmcb, VMCB_INTERCEPTS);
-
-       c = &svm->vmcb->control;
-       h = &svm->vmcb01.ptr->control;
-       g = &svm->nested.ctl;
+       vmcb_mark_dirty(vmcb02, VMCB_INTERCEPTS);
 
        for (i = 0; i < MAX_INTERCEPT; i++)
-               c->intercepts[i] = h->intercepts[i];
+               vmcb02->control.intercepts[i] = vmcb01->control.intercepts[i];
 
-       if (g->int_ctl & V_INTR_MASKING_MASK) {
+       if (vmcb12_ctrl->int_ctl & V_INTR_MASKING_MASK) {
                /*
                 * If L2 is active and V_INTR_MASKING is enabled in vmcb12,
                 * disable intercept of CR8 writes as L2's CR8 does not affect
@@ -151,17 +148,17 @@ void nested_vmcb02_recalc_intercepts(struct vcpu_svm *svm)
                 * the effective RFLAGS.IF for L1 interrupts will never be set
                 * while L2 is running (L2's RFLAGS.IF doesn't affect L1 IRQs).
                 */
-               vmcb_clr_intercept(c, INTERCEPT_CR8_WRITE);
-               if (!(svm->vmcb01.ptr->save.rflags & X86_EFLAGS_IF))
-                       vmcb_clr_intercept(c, INTERCEPT_VINTR);
+               vmcb_clr_intercept(&vmcb02->control, INTERCEPT_CR8_WRITE);
+               if (!(vmcb01->save.rflags & X86_EFLAGS_IF))
+                       vmcb_clr_intercept(&vmcb02->control, INTERCEPT_VINTR);
        }
 
        for (i = 0; i < MAX_INTERCEPT; i++)
-               c->intercepts[i] |= g->intercepts[i];
+               vmcb02->control.intercepts[i] |= vmcb12_ctrl->intercepts[i];
 
        /* If SMI is not intercepted, ignore guest SMI intercept as well  */
        if (!intercept_smi)
-               vmcb_clr_intercept(c, INTERCEPT_SMI);
+               vmcb_clr_intercept(&vmcb02->control, INTERCEPT_SMI);
 
        if (nested_vmcb_needs_vls_intercept(svm)) {
                /*
@@ -169,10 +166,10 @@ void nested_vmcb02_recalc_intercepts(struct vcpu_svm *svm)
                 * we must intercept these instructions to correctly
                 * emulate them in case L1 doesn't intercept them.
                 */
-               vmcb_set_intercept(c, INTERCEPT_VMLOAD);
-               vmcb_set_intercept(c, INTERCEPT_VMSAVE);
+               vmcb_set_intercept(&vmcb02->control, INTERCEPT_VMLOAD);
+               vmcb_set_intercept(&vmcb02->control, INTERCEPT_VMSAVE);
        } else {
-               WARN_ON(!(c->virt_ext & VIRTUAL_VMLOAD_VMSAVE_ENABLE_MASK));
+               WARN_ON_ONCE(!(vmcb02->control.virt_ext & VIRTUAL_VMLOAD_VMSAVE_ENABLE_MASK));
        }
 }