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    SubjectRe: [RFC v2 08/32] x86/traps: Add #VE support for TDX guest
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    On 6/8/21 10:48 AM, Sean Christopherson wrote:
    > On Tue, Jun 08, 2021, Dave Hansen wrote:
    >> On 4/26/21 11:01 AM, Kuppuswamy Sathyanarayanan wrote:
    >>> +#ifdef CONFIG_INTEL_TDX_GUEST
    >>> +DEFINE_IDTENTRY(exc_virtualization_exception)
    >>> +{
    >>> + struct ve_info ve;
    >>> + int ret;
    >>> +
    >>> + RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
    >>> +
    >>> + /*
    >>> + * Consume #VE info before re-enabling interrupts. It will be
    >>> + * re-enabled after executing the TDGETVEINFO TDCALL.
    >>> + */
    >>> + ret = tdg_get_ve_info(&ve);
    >> Is it safe to have *anything* before the tdg_get_ve_info()? For
    >> instance, say that RCU_LOCKDEP_WARN() triggers. Will anything in there
    >> do MMIO?
    > I doubt it's safe, anything that's doing printing has the potential to trigger
    > #VE. Even if we can prove it's safe for all possible paths, I can't think of a
    > reason to allow anything that's not absolutely necessary before retrieving the
    > #VE info.

    What about tracing? Can I plop a kprobe in here or turn on ftrace?

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