tools/testing/selftests/kvm/lib/x86_64/svm.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * tools/testing/selftests/kvm/lib/x86_64/svm.c
 * Helpers used for nested SVM testing
 * Largely inspired from KVM unit test svm.c
 *
 * Copyright (C) 2020, Red Hat, Inc.
 */

#include "test_util.h"
#include "kvm_util.h"
#include "../kvm_util_internal.h"
#include "processor.h"
#include "svm_util.h"

#define SEV_DEV_PATH "/dev/sev"

struct gpr64_regs guest_regs;
u64 rflags;

/* Allocate memory regions for nested SVM tests.
 *
 * Input Args:
 *   vm - The VM to allocate guest-virtual addresses in.
 *
 * Output Args:
 *   p_svm_gva - The guest virtual address for the struct svm_test_data.
 *
 * Return:
 *   Pointer to structure with the addresses of the SVM areas.
 */
struct svm_test_data *
vcpu_alloc_svm(struct kvm_vm *vm, vm_vaddr_t *p_svm_gva)
{
	vm_vaddr_t svm_gva = vm_vaddr_alloc_page(vm);
	struct svm_test_data *svm = addr_gva2hva(vm, svm_gva);

	svm->vmcb = (void *)vm_vaddr_alloc_page(vm);
	svm->vmcb_hva = addr_gva2hva(vm, (uintptr_t)svm->vmcb);
	svm->vmcb_gpa = addr_gva2gpa(vm, (uintptr_t)svm->vmcb);

	svm->save_area = (void *)vm_vaddr_alloc_page(vm);
	svm->save_area_hva = addr_gva2hva(vm, (uintptr_t)svm->save_area);
	svm->save_area_gpa = addr_gva2gpa(vm, (uintptr_t)svm->save_area);

	*p_svm_gva = svm_gva;
	return svm;
}

static void vmcb_set_seg(struct vmcb_seg *seg, u16 selector,
			 u64 base, u32 limit, u32 attr)
{
	seg->selector = selector;
	seg->attrib = attr;
	seg->limit = limit;
	seg->base = base;
}

/*
 * Avoid using memset to clear the vmcb, since libc may not be
 * available in L1 (and, even if it is, features that libc memset may
 * want to use, like AVX, may not be enabled).
 */
static void clear_vmcb(struct vmcb *vmcb)
{
	int n = sizeof(*vmcb) / sizeof(u32);

	asm volatile ("rep stosl" : "+c"(n), "+D"(vmcb) : "a"(0) : "memory");
}

void generic_svm_setup(struct svm_test_data *svm, void *guest_rip, void *guest_rsp)
{
	struct vmcb *vmcb = svm->vmcb;
	uint64_t vmcb_gpa = svm->vmcb_gpa;
	struct vmcb_save_area *save = &vmcb->save;
	struct vmcb_control_area *ctrl = &vmcb->control;
	u32 data_seg_attr = 3 | SVM_SELECTOR_S_MASK | SVM_SELECTOR_P_MASK
	      | SVM_SELECTOR_DB_MASK | SVM_SELECTOR_G_MASK;
	u32 code_seg_attr = 9 | SVM_SELECTOR_S_MASK | SVM_SELECTOR_P_MASK
		| SVM_SELECTOR_L_MASK | SVM_SELECTOR_G_MASK;
	uint64_t efer;

	efer = rdmsr(MSR_EFER);
	wrmsr(MSR_EFER, efer | EFER_SVME);
	wrmsr(MSR_VM_HSAVE_PA, svm->save_area_gpa);

	clear_vmcb(vmcb);
	asm volatile ("vmsave %0\n\t" : : "a" (vmcb_gpa) : "memory");
	vmcb_set_seg(&save->es, get_es(), 0, -1U, data_seg_attr);
	vmcb_set_seg(&save->cs, get_cs(), 0, -1U, code_seg_attr);
	vmcb_set_seg(&save->ss, get_ss(), 0, -1U, data_seg_attr);
	vmcb_set_seg(&save->ds, get_ds(), 0, -1U, data_seg_attr);
	vmcb_set_seg(&save->gdtr, 0, get_gdt().address, get_gdt().size, 0);
	vmcb_set_seg(&save->idtr, 0, get_idt().address, get_idt().size, 0);

	ctrl->asid = 1;
	save->cpl = 0;
	save->efer = rdmsr(MSR_EFER);
	asm volatile ("mov %%cr4, %0" : "=r"(save->cr4) : : "memory");
	asm volatile ("mov %%cr3, %0" : "=r"(save->cr3) : : "memory");
	asm volatile ("mov %%cr0, %0" : "=r"(save->cr0) : : "memory");
	asm volatile ("mov %%dr7, %0" : "=r"(save->dr7) : : "memory");
	asm volatile ("mov %%dr6, %0" : "=r"(save->dr6) : : "memory");
	asm volatile ("mov %%cr2, %0" : "=r"(save->cr2) : : "memory");
	save->g_pat = rdmsr(MSR_IA32_CR_PAT);
	save->dbgctl = rdmsr(MSR_IA32_DEBUGCTLMSR);
	ctrl->intercept = (1ULL << INTERCEPT_VMRUN) |
				(1ULL << INTERCEPT_VMMCALL);

	vmcb->save.rip = (u64)guest_rip;
	vmcb->save.rsp = (u64)guest_rsp;
	guest_regs.rdi = (u64)svm;
}

/*
 * save/restore 64-bit general registers except rax, rip, rsp
 * which are directly handed through the VMCB guest processor state
 */
#define SAVE_GPR_C				\
	"xchg %%rbx, guest_regs+0x20\n\t"	\
	"xchg %%rcx, guest_regs+0x10\n\t"	\
	"xchg %%rdx, guest_regs+0x18\n\t"	\
	"xchg %%rbp, guest_regs+0x30\n\t"	\
	"xchg %%rsi, guest_regs+0x38\n\t"	\
	"xchg %%rdi, guest_regs+0x40\n\t"	\
	"xchg %%r8,  guest_regs+0x48\n\t"	\
	"xchg %%r9,  guest_regs+0x50\n\t"	\
	"xchg %%r10, guest_regs+0x58\n\t"	\
	"xchg %%r11, guest_regs+0x60\n\t"	\
	"xchg %%r12, guest_regs+0x68\n\t"	\
	"xchg %%r13, guest_regs+0x70\n\t"	\
	"xchg %%r14, guest_regs+0x78\n\t"	\
	"xchg %%r15, guest_regs+0x80\n\t"

#define LOAD_GPR_C      SAVE_GPR_C

/*
 * selftests do not use interrupts so we dropped clgi/sti/cli/stgi
 * for now. registers involved in LOAD/SAVE_GPR_C are eventually
 * unmodified so they do not need to be in the clobber list.
 */
void run_guest(struct vmcb *vmcb, uint64_t vmcb_gpa)
{
	asm volatile (
		"vmload %[vmcb_gpa]\n\t"
		"mov rflags, %%r15\n\t"	// rflags
		"mov %%r15, 0x170(%[vmcb])\n\t"
		"mov guest_regs, %%r15\n\t"	// rax
		"mov %%r15, 0x1f8(%[vmcb])\n\t"
		LOAD_GPR_C
		"vmrun %[vmcb_gpa]\n\t"
		SAVE_GPR_C
		"mov 0x170(%[vmcb]), %%r15\n\t"	// rflags
		"mov %%r15, rflags\n\t"
		"mov 0x1f8(%[vmcb]), %%r15\n\t"	// rax
		"mov %%r15, guest_regs\n\t"
		"vmsave %[vmcb_gpa]\n\t"
		: : [vmcb] "r" (vmcb), [vmcb_gpa] "a" (vmcb_gpa)
		: "r15", "memory");
}

bool nested_svm_supported(void)
{
	struct kvm_cpuid_entry2 *entry =
		kvm_get_supported_cpuid_entry(0x80000001);

	return entry->ecx & CPUID_SVM;
}

void nested_svm_check_supported(void)
{
	if (!nested_svm_supported()) {
		print_skip("nested SVM not enabled");
		exit(KSFT_SKIP);
	}
}

/*
 * Open SEV_DEV_PATH if available, otherwise exit the entire program.
 *
 * Return:
 *   The opened file descriptor of /dev/sev.
 */
int open_sev_dev_path_or_exit(void)
{
	return open_path_or_exit(SEV_DEV_PATH, 0);
}