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