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

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Message-Id: <cd58659a-c3ec-427a-bf57-26fb8f61505c@www.fastmail.com>
Date:   Tue, 08 Jun 2021 11:17:47 -0700
From:   "Andy Lutomirski" <luto@...nel.org>
To:     "Dave Hansen" <dave.hansen@...el.com>,
        "Andi Kleen" <ak@...ux.intel.com>,
        "Sean Christopherson" <seanjc@...gle.com>
Cc:     "Sathyanarayanan Kuppuswamy" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "Williams, Dan J" <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 Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v2 08/32] x86/traps: Add #VE support for TDX guest



On Tue, Jun 8, 2021, at 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?
> 

We should do the get_ve_info in a noinstr region.