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Add an architecture specific ucall.h and inline the simple arch hooks, e.g. the init hook for everything except ARM, and the actual "do ucall" hook for everything except x86 (which should be simple, but temporarily isn't due to carrying a workaround). Having a per-arch ucall header will allow adding a #define for the expected KVM exit reason for a ucall that is colocated (for everything except x86) with the ucall itself. Reviewed-by: Andrew Jones <ajones@ventanamicro.com> Link: https://lore.kernel.org/r/20230731203026.1192091-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com>
57 lines
1.5 KiB
C
57 lines
1.5 KiB
C
// 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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