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KVM: VMX: Allow VM-Fail path of VMREAD helper to be instrumented

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Allow instrumentation in the VM-Fail path of __vmcs_readl() so that the
helper can be used in noinstr functions, e.g. to get the exit reason in
vmx_vcpu_enter_exit() in order to handle NMI VM-Exits in the noinstr
section.  While allowing instrumentation isn't technically safe, KVM has
much bigger problems if VMREAD fails in a noinstr section.

Note, all other VMX instructions also allow instrumentation in their
VM-Fail paths for similar reasons, VMREAD was simply omitted by commit
3ebccdf373c2 ("x86/kvm/vmx: Move guest enter/exit into .noinstr.text")
because VMREAD wasn't used in a noinstr section at the time.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221213060912.654668-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2022-12-13 06:09:07 +00:00
parent fc9465be8a
commit 8578f59657
1 changed files with 2 additions and 0 deletions
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2
arch/x86/kvm/vmx/vmx_ops.h
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@ -100,8 +100,10 @@ static __always_inline unsigned long __vmcs_readl(unsigned long field)
return value;
do_fail:
instrumentation_begin();
WARN_ONCE(1, KBUILD_MODNAME ": vmread failed: field=%lx\n", field);
pr_warn_ratelimited(KBUILD_MODNAME ": vmread failed: field=%lx\n", field);
instrumentation_end();
return 0;
do_exception: