KVM: VMX: Make VMREAD error path play nice with noinstr

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Mark vmread_error_trampoline() as noinstr, and add a second trampoline
for the CONFIG_CC_HAS_ASM_GOTO_OUTPUT=n case to enable instrumentation
when handling VM-Fail on VMREAD.  VMREAD is used in various noinstr
flows, e.g. immediately after VM-Exit, and objtool rightly complains that
the call to the error trampoline leaves a no-instrumentation section
without annotating that it's safe to do so.

  vmlinux.o: warning: objtool: vmx_vcpu_enter_exit+0xc9:
  call to vmread_error_trampoline() leaves .noinstr.text section

Note, strictly speaking, enabling instrumentation in the VM-Fail path
isn't exactly safe, but if VMREAD fails the kernel/system is likely hosed
anyways, and logging that there is a fatal error is more important than
*maybe* encountering slightly unsafe instrumentation.

Reported-by: Su Hui <suhui@nfschina.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230721235637.2345403-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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This commit is contained in:

Sean Christopherson 2023-07-21 16:56:36 -07:00 • committed by Paolo Bonzini

parent 5e1fe4a21c

commit c20d403fd0

3 changed files with 26 additions and 9 deletions

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8

arch/x86/kvm/vmx/vmenter.S

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20

arch/x86/kvm/vmx/vmx.c

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9

arch/x86/kvm/vmx/vmx_ops.h

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