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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"
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);
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, void *arg)
{
vm_paddr_t gpa, start, end, step, offset;
unsigned int 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 = min(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_FAIL("Can't find a ucall mmio address");
}
void ucall_uninit(struct kvm_vm *vm)
{
ucall_exit_mmio_addr = 0;
sync_global_to_guest(vm, ucall_exit_mmio_addr);
}
void ucall(uint64_t cmd, int nargs, ...)
{
struct ucall uc = {};
va_list va;
int i;
WRITE_ONCE(uc.cmd, cmd);
nargs = min(nargs, UCALL_MAX_ARGS);
va_start(va, nargs);
for (i = 0; i < nargs; ++i)
WRITE_ONCE(uc.args[i], va_arg(va, uint64_t));
va_end(va);
WRITE_ONCE(*ucall_exit_mmio_addr, (vm_vaddr_t)&uc);
}
uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
{
struct kvm_run *run = vcpu->run;
struct ucall ucall = {};
if (uc)
memset(uc, 0, sizeof(*uc));
if (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(vcpu->vm, gva), sizeof(ucall));
vcpu_run_complete_io(vcpu);
if (uc)
memcpy(uc, &ucall, sizeof(ucall));
}
return ucall.cmd;
}
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