90a48843a1
After commit e8bb4755eea2("KVM: selftests: Split ucall.c into architecture
specific files") selftests which use ucall on x86 started segfaulting and
apparently it's gcc to blame: it "optimizes" ucall() function throwing away
va_start/va_end part because it thinks the structure is not being used.
Previously, it couldn't do that because the there was also MMIO version and
the decision which particular implementation to use was done at runtime.
With older gccs it's possible to solve the problem by adding 'volatile'
to 'struct ucall' but at least with gcc-8.3 this trick doesn't work.
'memory' clobber seems to do the job.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
57 lines
1.1 KiB
C
57 lines
1.1 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_init(struct kvm_vm *vm, void *arg)
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{
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}
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void ucall_uninit(struct kvm_vm *vm)
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{
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}
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void ucall(uint64_t cmd, int nargs, ...)
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{
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struct ucall uc = {
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.cmd = cmd,
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};
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va_list va;
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int i;
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nargs = nargs <= UCALL_MAX_ARGS ? nargs : UCALL_MAX_ARGS;
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va_start(va, nargs);
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for (i = 0; i < nargs; ++i)
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uc.args[i] = va_arg(va, uint64_t);
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va_end(va);
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asm volatile("in %[port], %%al"
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: : [port] "d" (UCALL_PIO_PORT), "D" (&uc) : "rax", "memory");
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}
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uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc)
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{
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struct kvm_run *run = vcpu_state(vm, vcpu_id);
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struct ucall ucall = {};
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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(vm, vcpu_id, ®s);
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memcpy(&ucall, addr_gva2hva(vm, (vm_vaddr_t)regs.rdi),
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sizeof(ucall));
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vcpu_run_complete_io(vm, vcpu_id);
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if (uc)
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memcpy(uc, &ucall, sizeof(ucall));
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}
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return ucall.cmd;
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}
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