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1// SPDX-License-Identifier: GPL-2.02/*3 * ucall support. A ucall is a "hypercall to userspace".4 *5 * Copyright (C) 2018, Red Hat, Inc.6 */7#include "kvm_util.h"8 9#define UCALL_PIO_PORT ((uint16_t)0x1000)10 11void ucall_arch_do_ucall(vm_vaddr_t uc)12{13 /*14 * FIXME: Revert this hack (the entire commit that added it) once nVMX15 * preserves L2 GPRs across a nested VM-Exit. If a ucall from L2, e.g.16 * to do a GUEST_SYNC(), lands the vCPU in L1, any and all GPRs can be17 * clobbered by L1. Save and restore non-volatile GPRs (clobbering RBP18 * in particular is problematic) along with RDX and RDI (which are19 * inputs), and clobber volatile GPRs. *sigh*20 */21#define HORRIFIC_L2_UCALL_CLOBBER_HACK \22 "rcx", "rsi", "r8", "r9", "r10", "r11"23 24 asm volatile("push %%rbp\n\t"25 "push %%r15\n\t"26 "push %%r14\n\t"27 "push %%r13\n\t"28 "push %%r12\n\t"29 "push %%rbx\n\t"30 "push %%rdx\n\t"31 "push %%rdi\n\t"32 "in %[port], %%al\n\t"33 "pop %%rdi\n\t"34 "pop %%rdx\n\t"35 "pop %%rbx\n\t"36 "pop %%r12\n\t"37 "pop %%r13\n\t"38 "pop %%r14\n\t"39 "pop %%r15\n\t"40 "pop %%rbp\n\t"41 : : [port] "d" (UCALL_PIO_PORT), "D" (uc) : "rax", "memory",42 HORRIFIC_L2_UCALL_CLOBBER_HACK);43}44 45void *ucall_arch_get_ucall(struct kvm_vcpu *vcpu)46{47 struct kvm_run *run = vcpu->run;48 49 if (run->exit_reason == KVM_EXIT_IO && run->io.port == UCALL_PIO_PORT) {50 struct kvm_regs regs;51 52 vcpu_regs_get(vcpu, ®s);53 return (void *)regs.rdi;54 }55 return NULL;56}57