1 files changed, 56 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/lib/x86/ucall.c b/tools/testing/selftests/kvm/lib/x86/ucall.c
new file mode 100644
index 000000000000..1265cecc7dd1
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/x86/ucall.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ucall support. A ucall is a "hypercall to userspace".
+ *
+ * Copyright (C) 2018, Red Hat, Inc.
+ */
+#include "kvm_util.h"
+
+#define UCALL_PIO_PORT ((uint16_t)0x1000)
+
+void ucall_arch_do_ucall(vm_vaddr_t uc)
+{
+	/*
+	 * FIXME: Revert this hack (the entire commit that added it) once nVMX
+	 * preserves L2 GPRs across a nested VM-Exit.  If a ucall from L2, e.g.
+	 * to do a GUEST_SYNC(), lands the vCPU in L1, any and all GPRs can be
+	 * clobbered by L1.  Save and restore non-volatile GPRs (clobbering RBP
+	 * in particular is problematic) along with RDX and RDI (which are
+	 * inputs), and clobber volatile GPRs. *sigh*
+	 */
+#define HORRIFIC_L2_UCALL_CLOBBER_HACK	\
+	"rcx", "rsi", "r8", "r9", "r10", "r11"
+
+	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"
+		     "in %[port], %%al\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"
+		: : [port] "d" (UCALL_PIO_PORT), "D" (uc) : "rax", "memory",
+		     HORRIFIC_L2_UCALL_CLOBBER_HACK);
+}
+
+void *ucall_arch_get_ucall(struct kvm_vcpu *vcpu)
+{
+	struct kvm_run *run = vcpu->run;
+
+	if (run->exit_reason == KVM_EXIT_IO && run->io.port == UCALL_PIO_PORT) {
+		struct kvm_regs regs;
+
+		vcpu_regs_get(vcpu, &regs);
+		return (void *)regs.rdi;
+	}
+	return NULL;
+}