linux-kernel - Re: [RFC v2 08/32] x86/traps: Add #VE support for TDX guest

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Date:   Tue, 8 Jun 2021 11:18:07 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Dave Hansen <dave.hansen@...el.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Raj Ashok <ashok.raj@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 08/32] x86/traps: Add #VE support for TDX guest


On 6/8/2021 11:15 AM, Dave Hansen wrote:
> On 6/8/21 11:12 AM, Andi Kleen wrote:
>> 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)
> Can it do MMIO:
>
>> +DEFINE_IDTENTRY(exc_virtualization_exception)
>> +{
> =======> HERE
>> +    ret = tdg_get_ve_info(&ve);
> Recursion isn't the problem.  It would double-fault there, right?

Yes that's right. tp_printk already has a lot of other corner cases that 
break though, so it's not a real issue.

-Andi