Re: [PATCH v3 03/10] KVM: selftests: Add a test to verify APICv updates (while L2 is active)

[Sean Christopherson <seanjc@google.com>]

On Fri, Dec 12, 2025, Chao Gao wrote:
> On Fri, Dec 05, 2025 at 03:19:06PM -0800, Sean Christopherson wrote:
> >+static void bad_ipi_handler(struct ex_regs *regs)
> >+{
> >+	TEST_FAIL("Received \"bad\" IPI; ICR MMIO write should have been ignored");
> 
> is it ok to use TEST_FAIL() in guest code?

Doh.  Good point.  It'll definitely generate a failure, but not a very helpful one.

> >+static void l2_vmcall(void)
> >+{
> >+	/*
> >+	 * Exit to L1.  Assume all registers may be clobbered as selftests's
> >+	 * VM-Enter code doesn't preserve L2 GPRs.
> >+	 */
> >+	asm volatile("push %%rbp\n\t"
> >+		     "push %%r15\n\t"
> >+		     "push %%r14\n\t"
> >+		     "push %%r13\n\t"
> >+		     "push %%r12\n\t"
> >+		     "push %%rbx\n\t"
> >+		     "push %%rdx\n\t"
> >+		     "push %%rdi\n\t"
> >+		     "vmcall\n\t"
> >+		     "pop %%rdi\n\t"
> >+		     "pop %%rdx\n\t"
> >+		     "pop %%rbx\n\t"
> >+		     "pop %%r12\n\t"
> >+		     "pop %%r13\n\t"
> >+		     "pop %%r14\n\t"
> >+		     "pop %%r15\n\t"
> >+		     "pop %%rbp\n\t"
> >+		::: "rax", "rcx", "rdx", "rsi", "rdx", "r8", "r9", "r10", "r11", "memory");
> >+}
> 
> There's already a vmcall() helper in vmx.h. Why add a new one?

Oh, nice, I somehow missed that.

> >+int main(int argc, char *argv[])
> >+{
> >+	vm_vaddr_t vmx_pages_gva;
> >+	struct vmx_pages *vmx;
> >+	struct kvm_vcpu *vcpu;
> >+	struct kvm_vm *vm;
> >+	struct ucall uc;
> >+
> >+	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_VMX));
> >+
> >+	vm = vm_create_with_one_vcpu(&vcpu, l1_guest_code);
> >+
> >+	vmx = vcpu_alloc_vmx(vm, &vmx_pages_gva);
> >+	prepare_virtualize_apic_accesses(vmx, vm);
> >+	vcpu_args_set(vcpu, 2, vmx_pages_gva);
> 
> s/2/1
> 
> only one argument here.

Gah.  Thank you!