// SPDX-License-Identifier: GPL-2.0
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/*
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* ucall support. A ucall is a "hypercall to userspace".
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*
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* Copyright (C) 2018, Red Hat, Inc.
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*/
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#include "kvm_util.h"
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#include "../kvm_util_internal.h"
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static vm_vaddr_t *ucall_exit_mmio_addr;
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static bool ucall_mmio_init(struct kvm_vm *vm, vm_paddr_t gpa)
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{
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if (kvm_userspace_memory_region_find(vm, gpa, gpa + 1))
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return false;
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virt_pg_map(vm, gpa, gpa, 0);
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ucall_exit_mmio_addr = (vm_vaddr_t *)gpa;
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sync_global_to_guest(vm, ucall_exit_mmio_addr);
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return true;
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}
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void ucall_init(struct kvm_vm *vm, void *arg)
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{
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vm_paddr_t gpa, start, end, step, offset;
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unsigned int bits;
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bool ret;
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if (arg) {
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gpa = (vm_paddr_t)arg;
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ret = ucall_mmio_init(vm, gpa);
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TEST_ASSERT(ret, "Can't set ucall mmio address to %lx", gpa);
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return;
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}
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/*
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* Find an address within the allowed physical and virtual address
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* spaces, that does _not_ have a KVM memory region associated with
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* it. Identity mapping an address like this allows the guest to
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* access it, but as KVM doesn't know what to do with it, it
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* will assume it's something userspace handles and exit with
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* KVM_EXIT_MMIO. Well, at least that's how it works for AArch64.
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* Here we start with a guess that the addresses around 5/8th
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* of the allowed space are unmapped and then work both down and
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* up from there in 1/16th allowed space sized steps.
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*
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* Note, we need to use VA-bits - 1 when calculating the allowed
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* virtual address space for an identity mapping because the upper
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* half of the virtual address space is the two's complement of the
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* lower and won't match physical addresses.
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*/
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bits = vm->va_bits - 1;
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bits = vm->pa_bits < bits ? vm->pa_bits : bits;
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end = 1ul << bits;
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start = end * 5 / 8;
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step = end / 16;
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for (offset = 0; offset < end - start; offset += step) {
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if (ucall_mmio_init(vm, start - offset))
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return;
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if (ucall_mmio_init(vm, start + offset))
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return;
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}
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TEST_FAIL("Can't find a ucall mmio address");
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}
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void ucall_uninit(struct kvm_vm *vm)
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{
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ucall_exit_mmio_addr = 0;
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sync_global_to_guest(vm, ucall_exit_mmio_addr);
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}
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void ucall(uint64_t cmd, int nargs, ...)
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{
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struct ucall uc = {};
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va_list va;
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int i;
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WRITE_ONCE(uc.cmd, cmd);
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nargs = nargs <= UCALL_MAX_ARGS ? nargs : UCALL_MAX_ARGS;
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va_start(va, nargs);
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for (i = 0; i < nargs; ++i)
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WRITE_ONCE(uc.args[i], va_arg(va, uint64_t));
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va_end(va);
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WRITE_ONCE(*ucall_exit_mmio_addr, (vm_vaddr_t)&uc);
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}
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uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc)
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{
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struct kvm_run *run = vcpu_state(vm, vcpu_id);
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struct ucall ucall = {};
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if (uc)
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memset(uc, 0, sizeof(*uc));
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if (run->exit_reason == KVM_EXIT_MMIO &&
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run->mmio.phys_addr == (uint64_t)ucall_exit_mmio_addr) {
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vm_vaddr_t gva;
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TEST_ASSERT(run->mmio.is_write && run->mmio.len == 8,
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"Unexpected ucall exit mmio address access");
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memcpy(&gva, run->mmio.data, sizeof(gva));
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memcpy(&ucall, addr_gva2hva(vm, gva), sizeof(ucall));
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vcpu_run_complete_io(vm, vcpu_id);
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if (uc)
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memcpy(uc, &ucall, sizeof(ucall));
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}
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return ucall.cmd;
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}
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