Messages in this thread | | | Subject | Re: [RFC v2 08/32] x86/traps: Add #VE support for TDX guest | From | Andi Kleen <> | Date | Tue, 8 Jun 2021 11:12:48 -0700 |
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On 6/8/2021 10:53 AM, Dave Hansen wrote: > 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?
I believe neither does mmio/msr normally (except maybe ftrace+tp_printk, but that will likely work because it shouldn't recurse more than once due to ftrace's reentry protection)
-Andi
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