kvm: selftests: introduce ucall

Rework the guest exit to userspace code to generalize the concept
into what it is, a "hypercall to userspace", and provide two
implementations of it: the PortIO version currently used, but only
useable by x86, and an MMIO version that other architectures (except
s390) can use.

Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

3 files changed, 146 insertions, 14 deletions

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 6fd8c089cafc..4bd31bf04f53 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -133,6 +133,7 @@ struct kvm_vm *vm_create(enum vm_guest_mode mode, uint64_t phy_pages, int perm)
 	case VM_MODE_FLAT48PG:
 		vm->page_size = 0x1000;
 		vm->page_shift = 12;
+		vm->va_bits = 48;
 
 		/* Limit to 48-bit canonical virtual addresses. */
 		vm->vpages_valid = sparsebit_alloc();
@@ -1669,17 +1670,3 @@ void *addr_gva2hva(struct kvm_vm *vm, vm_vaddr_t gva)
 {
 	return addr_gpa2hva(vm, addr_gva2gpa(vm, gva));
 }
-
-void guest_args_read(struct kvm_vm *vm, uint32_t vcpu_id,
-		     struct guest_args *args)
-{
-	struct kvm_run *run = vcpu_state(vm, vcpu_id);
-	struct kvm_regs regs;
-
-	memset(&regs, 0, sizeof(regs));
-	vcpu_regs_get(vm, vcpu_id, &regs);
-
-	args->port = run->io.port;
-	args->arg0 = regs.rdi;
-	args->arg1 = regs.rsi;
-}
diff --git a/tools/testing/selftests/kvm/lib/kvm_util_internal.h b/tools/testing/selftests/kvm/lib/kvm_util_internal.h
index 542ed606b338..8fa7c9f7567a 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util_internal.h
+++ b/tools/testing/selftests/kvm/lib/kvm_util_internal.h
@@ -47,6 +47,7 @@ struct kvm_vm {
 	int fd;
 	unsigned int page_size;
 	unsigned int page_shift;
+	unsigned int va_bits;
 	uint64_t max_gfn;
 	struct vcpu *vcpu_head;
 	struct userspace_mem_region *userspace_mem_region_head;
diff --git a/tools/testing/selftests/kvm/lib/ucall.c b/tools/testing/selftests/kvm/lib/ucall.c
new file mode 100644
index 000000000000..4777f9bb5194
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/ucall.c
@@ -0,0 +1,144 @@
+// 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"
+#include "kvm_util_internal.h"
+
+#define UCALL_PIO_PORT ((uint16_t)0x1000)
+
+static ucall_type_t ucall_type;
+static vm_vaddr_t *ucall_exit_mmio_addr;
+
+static bool ucall_mmio_init(struct kvm_vm *vm, vm_paddr_t gpa)
+{
+	if (kvm_userspace_memory_region_find(vm, gpa, gpa + 1))
+		return false;
+
+	virt_pg_map(vm, gpa, gpa, 0);
+
+	ucall_exit_mmio_addr = (vm_vaddr_t *)gpa;
+	sync_global_to_guest(vm, ucall_exit_mmio_addr);
+
+	return true;
+}
+
+void ucall_init(struct kvm_vm *vm, ucall_type_t type, void *arg)
+{
+	ucall_type = type;
+	sync_global_to_guest(vm, ucall_type);
+
+	if (type == UCALL_PIO)
+		return;
+
+	if (type == UCALL_MMIO) {
+		vm_paddr_t gpa, start, end, step;
+		bool ret;
+
+		if (arg) {
+			gpa = (vm_paddr_t)arg;
+			ret = ucall_mmio_init(vm, gpa);
+			TEST_ASSERT(ret, "Can't set ucall mmio address to %lx", gpa);
+			return;
+		}
+
+		/*
+		 * Find an address within the allowed virtual address space,
+		 * that does _not_ have a KVM memory region associated with it.
+		 * Identity mapping an address like this allows the guest to
+		 * access it, but as KVM doesn't know what to do with it, it
+		 * will assume it's something userspace handles and exit with
+		 * KVM_EXIT_MMIO. Well, at least that's how it works for AArch64.
+		 * Here we start with a guess that the addresses around two
+		 * thirds of the VA space are unmapped and then work both down
+		 * and up from there in 1/6 VA space sized steps.
+		 */
+		start = 1ul << (vm->va_bits * 2 / 3);
+		end = 1ul << vm->va_bits;
+		step = 1ul << (vm->va_bits / 6);
+		for (gpa = start; gpa >= 0; gpa -= step) {
+			if (ucall_mmio_init(vm, gpa & ~(vm->page_size - 1)))
+				return;
+		}
+		for (gpa = start + step; gpa < end; gpa += step) {
+			if (ucall_mmio_init(vm, gpa & ~(vm->page_size - 1)))
+				return;
+		}
+		TEST_ASSERT(false, "Can't find a ucall mmio address");
+	}
+}
+
+void ucall_uninit(struct kvm_vm *vm)
+{
+	ucall_type = 0;
+	sync_global_to_guest(vm, ucall_type);
+	ucall_exit_mmio_addr = 0;
+	sync_global_to_guest(vm, ucall_exit_mmio_addr);
+}
+
+static void ucall_pio_exit(struct ucall *uc)
+{
+#ifdef __x86_64__
+	asm volatile("in %[port], %%al"
+		: : [port] "d" (UCALL_PIO_PORT), "D" (uc) : "rax");
+#endif
+}
+
+static void ucall_mmio_exit(struct ucall *uc)
+{
+	*ucall_exit_mmio_addr = (vm_vaddr_t)uc;
+}
+
+void ucall(uint64_t cmd, int nargs, ...)
+{
+	struct ucall uc = {
+		.cmd = cmd,
+	};
+	va_list va;
+	int i;
+
+	nargs = nargs <= UCALL_MAX_ARGS ? nargs : UCALL_MAX_ARGS;
+
+	va_start(va, nargs);
+	for (i = 0; i < nargs; ++i)
+		uc.args[i] = va_arg(va, uint64_t);
+	va_end(va);
+
+	switch (ucall_type) {
+	case UCALL_PIO:
+		ucall_pio_exit(&uc);
+		break;
+	case UCALL_MMIO:
+		ucall_mmio_exit(&uc);
+		break;
+	};
+}
+
+uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc)
+{
+	struct kvm_run *run = vcpu_state(vm, vcpu_id);
+
+	memset(uc, 0, sizeof(*uc));
+
+#ifdef __x86_64__
+	if (ucall_type == UCALL_PIO && run->exit_reason == KVM_EXIT_IO &&
+	    run->io.port == UCALL_PIO_PORT) {
+		struct kvm_regs regs;
+		vcpu_regs_get(vm, vcpu_id, &regs);
+		memcpy(uc, addr_gva2hva(vm, (vm_vaddr_t)regs.rdi), sizeof(*uc));
+		return uc->cmd;
+	}
+#endif
+	if (ucall_type == UCALL_MMIO && run->exit_reason == KVM_EXIT_MMIO &&
+	    run->mmio.phys_addr == (uint64_t)ucall_exit_mmio_addr) {
+		vm_vaddr_t gva;
+		TEST_ASSERT(run->mmio.is_write && run->mmio.len == 8,
+			    "Unexpected ucall exit mmio address access");
+		gva = *(vm_vaddr_t *)run->mmio.data;
+		memcpy(uc, addr_gva2hva(vm, gva), sizeof(*uc));
+	}
+
+	return uc->cmd;
+}