linux-kernel - Re: [RFC v2-fix-v1 3/3] x86/tdx: Handle port I/O

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Date:   Mon, 7 Jun 2021 19:57:43 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...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>,
        Sean Christopherson <seanjc@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v2-fix-v1 3/3] x86/tdx: Handle port I/O


ps://elixir.bootlin.com/linux/latest/source/kernel/printk/printk_safe.c#L382

> That depends on printk_nmi_direct_enter() to set the context, wouldn't
> an equivalent printk_ve_direct_enter() context flag be needed as well?

Even without it the console semaphore is always trylocked. So recursion 
is just not possible.

What would be possible is a endless loop (printk adding more information 
to the log buffer, which is then printed etc.), but that's true for 
everywhere in the console/serial driver subsystem.


-Andi