1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * ucall support. A ucall is a "hypercall to userspace". 4 * 5 * Copyright (C) 2018, Red Hat, Inc. 6 */ 7 #include "kvm_util.h" 8 #include "../kvm_util_internal.h" 9 10 static vm_vaddr_t *ucall_exit_mmio_addr; 11 12 static bool ucall_mmio_init(struct kvm_vm *vm, vm_paddr_t gpa) 13 { 14 if (kvm_userspace_memory_region_find(vm, gpa, gpa + 1)) 15 return false; 16 17 virt_pg_map(vm, gpa, gpa, 0); 18 19 ucall_exit_mmio_addr = (vm_vaddr_t *)gpa; 20 sync_global_to_guest(vm, ucall_exit_mmio_addr); 21 22 return true; 23 } 24 25 void ucall_init(struct kvm_vm *vm, void *arg) 26 { 27 vm_paddr_t gpa, start, end, step, offset; 28 unsigned int bits; 29 bool ret; 30 31 if (arg) { 32 gpa = (vm_paddr_t)arg; 33 ret = ucall_mmio_init(vm, gpa); 34 TEST_ASSERT(ret, "Can't set ucall mmio address to %lx", gpa); 35 return; 36 } 37 38 /* 39 * Find an address within the allowed physical and virtual address 40 * spaces, that does _not_ have a KVM memory region associated with 41 * it. Identity mapping an address like this allows the guest to 42 * access it, but as KVM doesn't know what to do with it, it 43 * will assume it's something userspace handles and exit with 44 * KVM_EXIT_MMIO. Well, at least that's how it works for AArch64. 45 * Here we start with a guess that the addresses around 5/8th 46 * of the allowed space are unmapped and then work both down and 47 * up from there in 1/16th allowed space sized steps. 48 * 49 * Note, we need to use VA-bits - 1 when calculating the allowed 50 * virtual address space for an identity mapping because the upper 51 * half of the virtual address space is the two's complement of the 52 * lower and won't match physical addresses. 53 */ 54 bits = vm->va_bits - 1; 55 bits = vm->pa_bits < bits ? vm->pa_bits : bits; 56 end = 1ul << bits; 57 start = end * 5 / 8; 58 step = end / 16; 59 for (offset = 0; offset < end - start; offset += step) { 60 if (ucall_mmio_init(vm, start - offset)) 61 return; 62 if (ucall_mmio_init(vm, start + offset)) 63 return; 64 } 65 TEST_FAIL("Can't find a ucall mmio address"); 66 } 67 68 void ucall_uninit(struct kvm_vm *vm) 69 { 70 ucall_exit_mmio_addr = 0; 71 sync_global_to_guest(vm, ucall_exit_mmio_addr); 72 } 73 74 void ucall(uint64_t cmd, int nargs, ...) 75 { 76 struct ucall uc = { 77 .cmd = cmd, 78 }; 79 va_list va; 80 int i; 81 82 nargs = nargs <= UCALL_MAX_ARGS ? nargs : UCALL_MAX_ARGS; 83 84 va_start(va, nargs); 85 for (i = 0; i < nargs; ++i) 86 uc.args[i] = va_arg(va, uint64_t); 87 va_end(va); 88 89 *ucall_exit_mmio_addr = (vm_vaddr_t)&uc; 90 } 91 92 uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc) 93 { 94 struct kvm_run *run = vcpu_state(vm, vcpu_id); 95 struct ucall ucall = {}; 96 97 if (uc) 98 memset(uc, 0, sizeof(*uc)); 99 100 if (run->exit_reason == KVM_EXIT_MMIO && 101 run->mmio.phys_addr == (uint64_t)ucall_exit_mmio_addr) { 102 vm_vaddr_t gva; 103 104 TEST_ASSERT(run->mmio.is_write && run->mmio.len == 8, 105 "Unexpected ucall exit mmio address access"); 106 memcpy(&gva, run->mmio.data, sizeof(gva)); 107 memcpy(&ucall, addr_gva2hva(vm, gva), sizeof(ucall)); 108 109 vcpu_run_complete_io(vm, vcpu_id); 110 if (uc) 111 memcpy(uc, &ucall, sizeof(ucall)); 112 } 113 114 return ucall.cmd; 115 } 116