7 files changed, 306 insertions, 175 deletions

diff --git a/tools/testing/selftests/kvm/lib/aarch64/processor.c b/tools/testing/selftests/kvm/lib/aarch64/processor.c
index 486400a97374..86036a59a668 100644
--- a/tools/testing/selftests/kvm/lib/aarch64/processor.c
+++ b/tools/testing/selftests/kvm/lib/aarch64/processor.c
@@ -264,6 +264,9 @@ void aarch64_vcpu_setup(struct kvm_vm *vm, int vcpuid, struct kvm_vcpu_init *ini
 	case VM_MODE_P52V48_4K:
 		TEST_ASSERT(false, "AArch64 does not support 4K sized pages "
 				   "with 52-bit physical address ranges");
+	case VM_MODE_PXXV48_4K:
+		TEST_ASSERT(false, "AArch64 does not support 4K sized pages "
+				   "with ANY-bit physical address ranges");
 	case VM_MODE_P52V48_64K:
 		tcr_el1 |= 1ul << 14; /* TG0 = 64KB */
 		tcr_el1 |= 6ul << 32; /* IPS = 52 bits */
diff --git a/tools/testing/selftests/kvm/lib/aarch64/ucall.c b/tools/testing/selftests/kvm/lib/aarch64/ucall.c
new file mode 100644
index 000000000000..6cd91970fbad
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/aarch64/ucall.c
@@ -0,0 +1,112 @@
+// 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"
+
+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, void *arg)
+{
+	vm_paddr_t gpa, start, end, step, offset;
+	unsigned int bits;
+	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 physical and virtual address
+	 * spaces, 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 5/8th
+	 * of the allowed space are unmapped and then work both down and
+	 * up from there in 1/16th allowed space sized steps.
+	 *
+	 * Note, we need to use VA-bits - 1 when calculating the allowed
+	 * virtual address space for an identity mapping because the upper
+	 * half of the virtual address space is the two's complement of the
+	 * lower and won't match physical addresses.
+	 */
+	bits = vm->va_bits - 1;
+	bits = vm->pa_bits < bits ? vm->pa_bits : bits;
+	end = 1ul << bits;
+	start = end * 5 / 8;
+	step = end / 16;
+	for (offset = 0; offset < end - start; offset += step) {
+		if (ucall_mmio_init(vm, start - offset))
+			return;
+		if (ucall_mmio_init(vm, start + offset))
+			return;
+	}
+	TEST_ASSERT(false, "Can't find a ucall mmio address");
+}
+
+void ucall_uninit(struct kvm_vm *vm)
+{
+	ucall_exit_mmio_addr = 0;
+	sync_global_to_guest(vm, ucall_exit_mmio_addr);
+}
+
+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);
+
+	*ucall_exit_mmio_addr = (vm_vaddr_t)&uc;
+}
+
+uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc)
+{
+	struct kvm_run *run = vcpu_state(vm, vcpu_id);
+	struct ucall ucall = {};
+
+	if (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");
+		memcpy(&gva, run->mmio.data, sizeof(gva));
+		memcpy(&ucall, addr_gva2hva(vm, gva), sizeof(ucall));
+
+		vcpu_run_complete_io(vm, vcpu_id);
+		if (uc)
+			memcpy(uc, &ucall, sizeof(ucall));
+	}
+
+	return ucall.cmd;
+}
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 6e49bb039376..80a338b5403c 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -8,6 +8,7 @@
 #include "test_util.h"
 #include "kvm_util.h"
 #include "kvm_util_internal.h"
+#include "processor.h"
 
 #include <assert.h>
 #include <sys/mman.h>
@@ -84,7 +85,7 @@ int vm_enable_cap(struct kvm_vm *vm, struct kvm_enable_cap *cap)
 	return ret;
 }
 
-static void vm_open(struct kvm_vm *vm, int perm, unsigned long type)
+static void vm_open(struct kvm_vm *vm, int perm)
 {
 	vm->kvm_fd = open(KVM_DEV_PATH, perm);
 	if (vm->kvm_fd < 0)
@@ -95,18 +96,19 @@ static void vm_open(struct kvm_vm *vm, int perm, unsigned long type)
 		exit(KSFT_SKIP);
 	}
 
-	vm->fd = ioctl(vm->kvm_fd, KVM_CREATE_VM, type);
+	vm->fd = ioctl(vm->kvm_fd, KVM_CREATE_VM, vm->type);
 	TEST_ASSERT(vm->fd >= 0, "KVM_CREATE_VM ioctl failed, "
 		"rc: %i errno: %i", vm->fd, errno);
 }
 
 const char * const vm_guest_mode_string[] = {
-	"PA-bits:52, VA-bits:48, 4K pages",
-	"PA-bits:52, VA-bits:48, 64K pages",
-	"PA-bits:48, VA-bits:48, 4K pages",
-	"PA-bits:48, VA-bits:48, 64K pages",
-	"PA-bits:40, VA-bits:48, 4K pages",
-	"PA-bits:40, VA-bits:48, 64K pages",
+	"PA-bits:52,  VA-bits:48,  4K pages",
+	"PA-bits:52,  VA-bits:48, 64K pages",
+	"PA-bits:48,  VA-bits:48,  4K pages",
+	"PA-bits:48,  VA-bits:48, 64K pages",
+	"PA-bits:40,  VA-bits:48,  4K pages",
+	"PA-bits:40,  VA-bits:48, 64K pages",
+	"PA-bits:ANY, VA-bits:48,  4K pages",
 };
 _Static_assert(sizeof(vm_guest_mode_string)/sizeof(char *) == NUM_VM_MODES,
 	       "Missing new mode strings?");
@@ -130,17 +132,17 @@ _Static_assert(sizeof(vm_guest_mode_string)/sizeof(char *) == NUM_VM_MODES,
  * descriptor to control the created VM is created with the permissions
  * given by perm (e.g. O_RDWR).
  */
-struct kvm_vm *_vm_create(enum vm_guest_mode mode, uint64_t phy_pages,
-			  int perm, unsigned long type)
+struct kvm_vm *_vm_create(enum vm_guest_mode mode, uint64_t phy_pages, int perm)
 {
 	struct kvm_vm *vm;
 
+	DEBUG("Testing guest mode: %s\n", vm_guest_mode_string(mode));
+
 	vm = calloc(1, sizeof(*vm));
 	TEST_ASSERT(vm != NULL, "Insufficient Memory");
 
 	vm->mode = mode;
-	vm->type = type;
-	vm_open(vm, perm, type);
+	vm->type = 0;
 
 	/* Setup mode specific traits. */
 	switch (vm->mode) {
@@ -186,10 +188,32 @@ struct kvm_vm *_vm_create(enum vm_guest_mode mode, uint64_t phy_pages,
 		vm->page_size = 0x10000;
 		vm->page_shift = 16;
 		break;
+	case VM_MODE_PXXV48_4K:
+#ifdef __x86_64__
+		kvm_get_cpu_address_width(&vm->pa_bits, &vm->va_bits);
+		TEST_ASSERT(vm->va_bits == 48, "Linear address width "
+			    "(%d bits) not supported", vm->va_bits);
+		vm->pgtable_levels = 4;
+		vm->page_size = 0x1000;
+		vm->page_shift = 12;
+		DEBUG("Guest physical address width detected: %d\n",
+		      vm->pa_bits);
+#else
+		TEST_ASSERT(false, "VM_MODE_PXXV48_4K not supported on "
+			    "non-x86 platforms");
+#endif
+		break;
 	default:
 		TEST_ASSERT(false, "Unknown guest mode, mode: 0x%x", mode);
 	}
 
+#ifdef __aarch64__
+	if (vm->pa_bits != 40)
+		vm->type = KVM_VM_TYPE_ARM_IPA_SIZE(vm->pa_bits);
+#endif
+
+	vm_open(vm, perm);
+
 	/* Limit to VA-bit canonical virtual addresses. */
 	vm->vpages_valid = sparsebit_alloc();
 	sparsebit_set_num(vm->vpages_valid,
@@ -212,7 +236,7 @@ struct kvm_vm *_vm_create(enum vm_guest_mode mode, uint64_t phy_pages,
 
 struct kvm_vm *vm_create(enum vm_guest_mode mode, uint64_t phy_pages, int perm)
 {
-	return _vm_create(mode, phy_pages, perm, 0);
+	return _vm_create(mode, phy_pages, perm);
 }
 
 /*
@@ -232,7 +256,7 @@ void kvm_vm_restart(struct kvm_vm *vmp, int perm)
 {
 	struct userspace_mem_region *region;
 
-	vm_open(vmp, perm, vmp->type);
+	vm_open(vmp, perm);
 	if (vmp->has_irqchip)
 		vm_create_irqchip(vmp);
 
@@ -1628,3 +1652,18 @@ bool vm_is_unrestricted_guest(struct kvm_vm *vm)
 
 	return val == 'Y';
 }
+
+unsigned int vm_get_page_size(struct kvm_vm *vm)
+{
+	return vm->page_size;
+}
+
+unsigned int vm_get_page_shift(struct kvm_vm *vm)
+{
+	return vm->page_shift;
+}
+
+unsigned int vm_get_max_gfn(struct kvm_vm *vm)
+{
+	return vm->max_gfn;
+}
diff --git a/tools/testing/selftests/kvm/lib/s390x/ucall.c b/tools/testing/selftests/kvm/lib/s390x/ucall.c
new file mode 100644
index 000000000000..fd589dc9bfab
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/s390x/ucall.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ucall support. A ucall is a "hypercall to userspace".
+ *
+ * Copyright (C) 2019 Red Hat, Inc.
+ */
+#include "kvm_util.h"
+
+void ucall_init(struct kvm_vm *vm, void *arg)
+{
+}
+
+void ucall_uninit(struct kvm_vm *vm)
+{
+}
+
+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);
+
+	/* Exit via DIAGNOSE 0x501 (normally used for breakpoints) */
+	asm volatile ("diag 0,%0,0x501" : : "a"(&uc) : "memory");
+}
+
+uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc)
+{
+	struct kvm_run *run = vcpu_state(vm, vcpu_id);
+	struct ucall ucall = {};
+
+	if (run->exit_reason == KVM_EXIT_S390_SIEIC &&
+	    run->s390_sieic.icptcode == 4 &&
+	    (run->s390_sieic.ipa >> 8) == 0x83 &&    /* 0x83 means DIAGNOSE */
+	    (run->s390_sieic.ipb >> 16) == 0x501) {
+		int reg = run->s390_sieic.ipa & 0xf;
+
+		memcpy(&ucall, addr_gva2hva(vm, run->s.regs.gprs[reg]),
+		       sizeof(ucall));
+
+		vcpu_run_complete_io(vm, vcpu_id);
+		if (uc)
+			memcpy(uc, &ucall, sizeof(ucall));
+	}
+
+	return ucall.cmd;
+}
diff --git a/tools/testing/selftests/kvm/lib/ucall.c b/tools/testing/selftests/kvm/lib/ucall.c
deleted file mode 100644
index dd9a66700f96..000000000000
--- a/tools/testing/selftests/kvm/lib/ucall.c
+++ /dev/null
@@ -1,157 +0,0 @@
-// 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, offset;
-		unsigned bits;
-		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 physical and virtual address
-		 * spaces, 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 5/8th
-		 * of the allowed space are unmapped and then work both down and
-		 * up from there in 1/16th allowed space sized steps.
-		 *
-		 * Note, we need to use VA-bits - 1 when calculating the allowed
-		 * virtual address space for an identity mapping because the upper
-		 * half of the virtual address space is the two's complement of the
-		 * lower and won't match physical addresses.
-		 */
-		bits = vm->va_bits - 1;
-		bits = vm->pa_bits < bits ? vm->pa_bits : bits;
-		end = 1ul << bits;
-		start = end * 5 / 8;
-		step = end / 16;
-		for (offset = 0; offset < end - start; offset += step) {
-			if (ucall_mmio_init(vm, start - offset))
-				return;
-			if (ucall_mmio_init(vm, start + offset))
-				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);
-	struct ucall ucall = {};
-	bool got_ucall = false;
-
-#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(&ucall, addr_gva2hva(vm, (vm_vaddr_t)regs.rdi), sizeof(ucall));
-		got_ucall = true;
-	}
-#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");
-		memcpy(&gva, run->mmio.data, sizeof(gva));
-		memcpy(&ucall, addr_gva2hva(vm, gva), sizeof(ucall));
-		got_ucall = true;
-	}
-
-	if (got_ucall) {
-		vcpu_run_complete_io(vm, vcpu_id);
-		if (uc)
-			memcpy(uc, &ucall, sizeof(ucall));
-	}
-
-	return ucall.cmd;
-}
diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index 0a5e487dbc50..c53dbc6bc568 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -228,7 +228,7 @@ void sregs_dump(FILE *stream, struct kvm_sregs *sregs,
 
 void virt_pgd_alloc(struct kvm_vm *vm, uint32_t pgd_memslot)
 {
-	TEST_ASSERT(vm->mode == VM_MODE_P52V48_4K, "Attempt to use "
+	TEST_ASSERT(vm->mode == VM_MODE_PXXV48_4K, "Attempt to use "
 		"unknown or unsupported guest mode, mode: 0x%x", vm->mode);
 
 	/* If needed, create page map l4 table. */
@@ -261,7 +261,7 @@ void virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
 	uint16_t index[4];
 	struct pageMapL4Entry *pml4e;
 
-	TEST_ASSERT(vm->mode == VM_MODE_P52V48_4K, "Attempt to use "
+	TEST_ASSERT(vm->mode == VM_MODE_PXXV48_4K, "Attempt to use "
 		"unknown or unsupported guest mode, mode: 0x%x", vm->mode);
 
 	TEST_ASSERT((vaddr % vm->page_size) == 0,
@@ -547,7 +547,7 @@ vm_paddr_t addr_gva2gpa(struct kvm_vm *vm, vm_vaddr_t gva)
 	struct pageDirectoryEntry *pde;
 	struct pageTableEntry *pte;
 
-	TEST_ASSERT(vm->mode == VM_MODE_P52V48_4K, "Attempt to use "
+	TEST_ASSERT(vm->mode == VM_MODE_PXXV48_4K, "Attempt to use "
 		"unknown or unsupported guest mode, mode: 0x%x", vm->mode);
 
 	index[0] = (gva >> 12) & 0x1ffu;
@@ -621,7 +621,7 @@ static void vcpu_setup(struct kvm_vm *vm, int vcpuid, int pgd_memslot, int gdt_m
 	kvm_setup_gdt(vm, &sregs.gdt, gdt_memslot, pgd_memslot);
 
 	switch (vm->mode) {
-	case VM_MODE_P52V48_4K:
+	case VM_MODE_PXXV48_4K:
 		sregs.cr0 = X86_CR0_PE | X86_CR0_NE | X86_CR0_PG;
 		sregs.cr4 |= X86_CR4_PAE | X86_CR4_OSFXSR;
 		sregs.efer |= (EFER_LME | EFER_LMA | EFER_NX);
@@ -1157,3 +1157,25 @@ bool is_intel_cpu(void)
 	chunk = (const uint32_t *)("GenuineIntel");
 	return (ebx == chunk[0] && edx == chunk[1] && ecx == chunk[2]);
 }
+
+uint32_t kvm_get_cpuid_max(void)
+{
+	return kvm_get_supported_cpuid_entry(0x80000000)->eax;
+}
+
+void kvm_get_cpu_address_width(unsigned int *pa_bits, unsigned int *va_bits)
+{
+	struct kvm_cpuid_entry2 *entry;
+	bool pae;
+
+	/* SDM 4.1.4 */
+	if (kvm_get_cpuid_max() < 0x80000008) {
+		pae = kvm_get_supported_cpuid_entry(1)->edx & (1 << 6);
+		*pa_bits = pae ? 36 : 32;
+		*va_bits = 32;
+	} else {
+		entry = kvm_get_supported_cpuid_entry(0x80000008);
+		*pa_bits = entry->eax & 0xff;
+		*va_bits = (entry->eax >> 8) & 0xff;
+	}
+}
diff --git a/tools/testing/selftests/kvm/lib/x86_64/ucall.c b/tools/testing/selftests/kvm/lib/x86_64/ucall.c
new file mode 100644
index 000000000000..da4d89ad5419
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/x86_64/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_init(struct kvm_vm *vm, void *arg)
+{
+}
+
+void ucall_uninit(struct kvm_vm *vm)
+{
+}
+
+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);
+
+	asm volatile("in %[port], %%al"
+		: : [port] "d" (UCALL_PIO_PORT), "D" (&uc) : "rax", "memory");
+}
+
+uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc)
+{
+	struct kvm_run *run = vcpu_state(vm, vcpu_id);
+	struct ucall ucall = {};
+
+	if (run->exit_reason == KVM_EXIT_IO && run->io.port == UCALL_PIO_PORT) {
+		struct kvm_regs regs;
+
+		vcpu_regs_get(vm, vcpu_id, &regs);
+		memcpy(&ucall, addr_gva2hva(vm, (vm_vaddr_t)regs.rdi),
+		       sizeof(ucall));
+
+		vcpu_run_complete_io(vm, vcpu_id);
+		if (uc)
+			memcpy(uc, &ucall, sizeof(ucall));
+	}
+
+	return ucall.cmd;
+}