linux-kernel - Re: [PATCH v5 08/12] x86/tdx: Add HLT support for TDX guest

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Message-ID: <YSUxeabIb30oibG5@zn.tnic>
Date:   Tue, 24 Aug 2021 19:50:49 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Peter H Anvin <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 08/12] x86/tdx: Add HLT support for TDX guest

On Tue, Aug 24, 2021 at 05:47:25PM +0000, Sean Christopherson wrote:
> It's passed to the (untrusted) VMM.  The TDX Module has direct access to the guest's
> entire FLAGS via the VMCS.
> 
> The VMM uses the "IRQs enabled" param to understand whether or not it should
> schedule the halted vCPU if an IRQ becomes pending.  E.g. if IRQs are disabled
> the VMM can keep the vCPU in virtual HLT, even if an IRQ is pending, without
> hanging/breaking the guest.

See, explanations like that need to be over those _tdx_hypercall()
wrappers. Otherwise it is just random magic.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette