| // 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" |
| |
| #define UCALL_PIO_PORT ((uint16_t)0x1000) |
| |
| void ucall_arch_do_ucall(vm_vaddr_t uc) |
| { |
| /* |
| * FIXME: Revert this hack (the entire commit that added it) once nVMX |
| * preserves L2 GPRs across a nested VM-Exit. If a ucall from L2, e.g. |
| * to do a GUEST_SYNC(), lands the vCPU in L1, any and all GPRs can be |
| * clobbered by L1. Save and restore non-volatile GPRs (clobbering RBP |
| * in particular is problematic) along with RDX and RDI (which are |
| * inputs), and clobber volatile GPRs. *sigh* |
| */ |
| #define HORRIFIC_L2_UCALL_CLOBBER_HACK \ |
| "rcx", "rsi", "r8", "r9", "r10", "r11" |
| |
| asm volatile("push %%rbp\n\t" |
| "push %%r15\n\t" |
| "push %%r14\n\t" |
| "push %%r13\n\t" |
| "push %%r12\n\t" |
| "push %%rbx\n\t" |
| "push %%rdx\n\t" |
| "push %%rdi\n\t" |
| "in %[port], %%al\n\t" |
| "pop %%rdi\n\t" |
| "pop %%rdx\n\t" |
| "pop %%rbx\n\t" |
| "pop %%r12\n\t" |
| "pop %%r13\n\t" |
| "pop %%r14\n\t" |
| "pop %%r15\n\t" |
| "pop %%rbp\n\t" |
| : : [port] "d" (UCALL_PIO_PORT), "D" (uc) : "rax", "memory", |
| HORRIFIC_L2_UCALL_CLOBBER_HACK); |
| } |
| |
| void *ucall_arch_get_ucall(struct kvm_vcpu *vcpu) |
| { |
| struct kvm_run *run = vcpu->run; |
| |
| if (run->exit_reason == KVM_EXIT_IO && run->io.port == UCALL_PIO_PORT) { |
| struct kvm_regs regs; |
| |
| vcpu_regs_get(vcpu, ®s); |
| return (void *)regs.rdi; |
| } |
| return NULL; |
| } |
