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// 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, ®s);
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;
}
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