gtests/tests/vmx_tsc_adjust_test.c

/*
 * gtests/tests/vmx_tsc_adjust_test.c
 *
 * Copyright (C) 2018, Google LLC.
 *
 * This work is licensed under the terms of the GNU GPL, version 2.
 *
 *
 * IA32_TSC_ADJUST test
 *
 * According to the SDM, "if an execution of WRMSR to the
 * IA32_TIME_STAMP_COUNTER MSR adds (or subtracts) value X from the TSC,
 * the logical processor also adds (or subtracts) value X from the
 * IA32_TSC_ADJUST MSR.
 *
 * Note that when L1 doesn't intercept writes to IA32_TSC, a
 * WRMSR(IA32_TSC) from L2 sets L1's TSC value, not L2's perceived TSC
 * value.
 *
 * This test verifies that this unusual case is handled correctly.
 */

#include "test_util.h"
#include "kvm_util.h"
#include "x86.h"
#include "vmx.h"

#include <string.h>
#include <sys/ioctl.h>

#ifndef MSR_IA32_TSC_ADJUST
#define MSR_IA32_TSC_ADJUST 0x3b
#endif

#define PAGE_SIZE	4096
#define VCPU_ID		5

#define TSC_ADJUST_VALUE (1ll << 32)
#define TSC_OFFSET_VALUE -(1ll << 48)

enum {
	PORT_ABORT = 0x1000,
	PORT_REPORT,
	PORT_DONE,
};

struct vmx_page {
	vm_vaddr_t virt;
	vm_paddr_t phys;
};

enum {
	VMXON_PAGE = 0,
	VMCS_PAGE,
	MSR_BITMAP_PAGE,

	NUM_VMX_PAGES,
};

struct kvm_single_msr {
	struct kvm_msrs header;
	struct kvm_msr_entry entry;
} __attribute__((packed));

/* The virtual machine object. */
static kvm_util_vm_t *vm;

/* Array of vmx_page descriptors that is shared with the guest. */
struct vmx_page *vmx_pages;

static void __exit_to_l0(uint16_t port, unsigned long arg)
{
	__asm__ __volatile__("in %[port], %%al"
		:
		: [port]"d"(port), "D"(arg)
		: "rax");
}

#define exit_to_l0(_port, _arg) __exit_to_l0(_port, (unsigned long) (_arg))

#define GUEST_ASSERT(_condition) do {					     \
	if (!(_condition))						     \
		exit_to_l0(PORT_ABORT, "Failed guest assert: " #_condition); \
} while (0)

static void check_ia32_tsc_adjust(int64_t max)
{
	int64_t adjust;

	adjust = rdmsr(MSR_IA32_TSC_ADJUST);
	exit_to_l0(PORT_REPORT, adjust);
	GUEST_ASSERT(adjust <= max);
}

static void l2_guest_code(void)
{
	uint64_t l1_tsc = rdtsc() - TSC_OFFSET_VALUE;

	wrmsr(MSR_IA32_TSC, l1_tsc - TSC_ADJUST_VALUE);
	check_ia32_tsc_adjust(-2 * TSC_ADJUST_VALUE);

	/* Exit to L1 */
	__asm__ __volatile__("vmcall");
}

static void l1_guest_code(struct vmx_page *vmx_pages)
{
#define L2_GUEST_STACK_SIZE 64
	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
	uint32_t control;

	wrmsr(MSR_IA32_TSC, rdtsc() - TSC_ADJUST_VALUE);
	check_ia32_tsc_adjust(-1 * TSC_ADJUST_VALUE);

	prepare_for_vmx_operation();

	/* Enter VMX root operation. */
	*(uint32_t *)vmx_pages[VMXON_PAGE].virt = vmcs_revision();
	GUEST_ASSERT(!vmxon(vmx_pages[VMXON_PAGE].phys));

	/* Load a VMCS. */
	*(uint32_t *)vmx_pages[VMCS_PAGE].virt = vmcs_revision();
	GUEST_ASSERT(!vmclear(vmx_pages[VMCS_PAGE].phys));
	GUEST_ASSERT(!vmptrld(vmx_pages[VMCS_PAGE].phys));

	/* Prepare the VMCS for L2 execution. */
	prepare_vmcs(l2_guest_code, &l2_guest_stack[L2_GUEST_STACK_SIZE]);
	control = vmreadz(CPU_BASED_VM_EXEC_CONTROL);
	control |= CPU_BASED_USE_MSR_BITMAPS | CPU_BASED_USE_TSC_OFFSETING;
	vmwrite(CPU_BASED_VM_EXEC_CONTROL, control);
	vmwrite(MSR_BITMAP, vmx_pages[MSR_BITMAP_PAGE].phys);
	vmwrite(TSC_OFFSET, TSC_OFFSET_VALUE);

	/* Jump into L2. */
	GUEST_ASSERT(!vmlaunch());
	GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_VMCALL);

	check_ia32_tsc_adjust(-2 * TSC_ADJUST_VALUE);

	exit_to_l0(PORT_DONE, 0);
}

static void allocate_vmx_page(struct vmx_page *page)
{
	vm_vaddr_t virt;

	virt = vm_vaddr_alloc(vm, PAGE_SIZE, 0, 0, 0);
	memset(addr_vmvirt2hvirt(vm, virt), 0, PAGE_SIZE);

	page->virt = virt;
	page->phys = addr_vmvirt2vmphy(vm, virt);
}

static vm_vaddr_t allocate_vmx_pages(void)
{
	vm_vaddr_t vmx_pages_vaddr;
	int i;

	vmx_pages_vaddr = vm_vaddr_alloc(
		vm, sizeof(struct vmx_page) * NUM_VMX_PAGES, 0, 0, 0);

	vmx_pages = (void *) addr_vmvirt2hvirt(vm, vmx_pages_vaddr);

	for (i = 0; i < NUM_VMX_PAGES; i++)
		allocate_vmx_page(&vmx_pages[i]);

	return vmx_pages_vaddr;
}

void report(int64_t val)
{
	fprintf(stderr,
		"IA32_TSC_ADJUST is %ld (%lld * TSC_ADJUST_VALUE + %lld).\n",
		val, val / TSC_ADJUST_VALUE, val % TSC_ADJUST_VALUE);
}

int main(int argc, char *argv[])
{
	vm_vaddr_t vmx_pages_vaddr;

	vm = vm_create_default_vmx(VCPU_ID, (void *) l1_guest_code);

	/* Allocate VMX pages and shared descriptors (vmx_pages). */
	vmx_pages_vaddr = allocate_vmx_pages();
	vcpu_args_set(vm, VCPU_ID, 1, vmx_pages_vaddr);

	for (;;) {
		volatile struct kvm_run *run = vcpu_state(vm, VCPU_ID);
		struct kvm_regs regs;

		vcpu_run(vm, VCPU_ID);
		TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
			    "Got exit_reason other than KVM_EXIT_IO: %u (%s),\n",
			    run->exit_reason,
			    exit_reason_str(run->exit_reason));

		vcpu_regs_get(vm, VCPU_ID, &regs);

		switch (run->io.port) {
		case PORT_ABORT:
			TEST_ASSERT(false, "%s", (const char *) regs.rdi);
			/* NOT REACHED */
		case PORT_REPORT:
			report(regs.rdi);
			break;
		case PORT_DONE:
			goto done;
		default:
			TEST_ASSERT(false, "Unknown port 0x%x.", run->io.port);
		}
	}

done:
	return 0;
}