tools/testing/selftests/kvm/lib/aarch64/ucall.c

   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);
  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         va_list va;
  78         int i;
  79
  80         WRITE_ONCE(uc.cmd, cmd);
  81         nargs = nargs <= UCALL_MAX_ARGS ? nargs : UCALL_MAX_ARGS;
  82
  83         va_start(va, nargs);
  84         for (i = 0; i < nargs; ++i)
  85                 WRITE_ONCE(uc.args[i], va_arg(va, uint64_t));
  86         va_end(va);
  87
  88         WRITE_ONCE(*ucall_exit_mmio_addr, (vm_vaddr_t)&uc);
  89 }
  90
  91 uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc)
  92 {
  93         struct kvm_run *run = vcpu_state(vm, vcpu_id);
  94         struct ucall ucall = {};
  95
  96         if (uc)
  97                 memset(uc, 0, sizeof(*uc));
  98
  99         if (run->exit_reason == KVM_EXIT_MMIO &&
 100             run->mmio.phys_addr == (uint64_t)ucall_exit_mmio_addr) {
 101                 vm_vaddr_t gva;
 102
 103                 TEST_ASSERT(run->mmio.is_write && run->mmio.len == 8,
 104                             "Unexpected ucall exit mmio address access");
 105                 memcpy(&gva, run->mmio.data, sizeof(gva));
 106                 memcpy(&ucall, addr_gva2hva(vm, gva), sizeof(ucall));
 107
 108                 vcpu_run_complete_io(vm, vcpu_id);
 109                 if (uc)
 110                         memcpy(uc, &ucall, sizeof(ucall));
 111         }
 112
 113         return ucall.cmd;
 114 }