lib/riscv/ucall.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * ucall support. A ucall is a "hypercall to userspace".
0004  *
0005  * Copyright (C) 2021 Western Digital Corporation or its affiliates.
0006  */
0007
0008 #include <linux/kvm.h>
0009
0010 #include "kvm_util.h"
0011 #include "processor.h"
0012
0013 void ucall_init(struct kvm_vm *vm, void *arg)
0014 {
0015 }
0016
0017 void ucall_uninit(struct kvm_vm *vm)
0018 {
0019 }
0020
0021 struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,
0022             unsigned long arg1, unsigned long arg2,
0023             unsigned long arg3, unsigned long arg4,
0024             unsigned long arg5)
0025 {
0026     register uintptr_t a0 asm ("a0") = (uintptr_t)(arg0);
0027     register uintptr_t a1 asm ("a1") = (uintptr_t)(arg1);
0028     register uintptr_t a2 asm ("a2") = (uintptr_t)(arg2);
0029     register uintptr_t a3 asm ("a3") = (uintptr_t)(arg3);
0030     register uintptr_t a4 asm ("a4") = (uintptr_t)(arg4);
0031     register uintptr_t a5 asm ("a5") = (uintptr_t)(arg5);
0032     register uintptr_t a6 asm ("a6") = (uintptr_t)(fid);
0033     register uintptr_t a7 asm ("a7") = (uintptr_t)(ext);
0034     struct sbiret ret;
0035
0036     asm volatile (
0037         "ecall"
0038         : "+r" (a0), "+r" (a1)
0039         : "r" (a2), "r" (a3), "r" (a4), "r" (a5), "r" (a6), "r" (a7)
0040         : "memory");
0041     ret.error = a0;
0042     ret.value = a1;
0043
0044     return ret;
0045 }
0046
0047 void ucall(uint64_t cmd, int nargs, ...)
0048 {
0049     struct ucall uc = {
0050         .cmd = cmd,
0051     };
0052     va_list va;
0053     int i;
0054
0055     nargs = min(nargs, UCALL_MAX_ARGS);
0056
0057     va_start(va, nargs);
0058     for (i = 0; i < nargs; ++i)
0059         uc.args[i] = va_arg(va, uint64_t);
0060     va_end(va);
0061
0062     sbi_ecall(KVM_RISCV_SELFTESTS_SBI_EXT,
0063           KVM_RISCV_SELFTESTS_SBI_UCALL,
0064           (vm_vaddr_t)&uc, 0, 0, 0, 0, 0);
0065 }
0066
0067 uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
0068 {
0069     struct kvm_run *run = vcpu->run;
0070     struct ucall ucall = {};
0071
0072     if (uc)
0073         memset(uc, 0, sizeof(*uc));
0074
0075     if (run->exit_reason == KVM_EXIT_RISCV_SBI &&
0076         run->riscv_sbi.extension_id == KVM_RISCV_SELFTESTS_SBI_EXT) {
0077         switch (run->riscv_sbi.function_id) {
0078         case KVM_RISCV_SELFTESTS_SBI_UCALL:
0079             memcpy(&ucall,
0080                    addr_gva2hva(vcpu->vm, run->riscv_sbi.args[0]),
0081                    sizeof(ucall));
0082
0083             vcpu_run_complete_io(vcpu);
0084             if (uc)
0085                 memcpy(uc, &ucall, sizeof(ucall));
0086
0087             break;
0088         case KVM_RISCV_SELFTESTS_SBI_UNEXP:
0089             vcpu_dump(stderr, vcpu, 2);
0090             TEST_ASSERT(0, "Unexpected trap taken by guest");
0091             break;
0092         default:
0093             break;
0094         }
0095     }
0096
0097     return ucall.cmd;
0098 }