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Subject: Re: [PATCH v5 08/12] x86/tdx: Add HLT support for TDX guest
To:     Borislav Petkov <bp@alien8.de>,
        Sean Christopherson <seanjc@google.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        Peter H Anvin <hpa@zytor.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Kirill Shutemov <kirill.shutemov@linux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
        x86@kernel.org, linux-kernel@vger.kernel.org
References: <20210804181329.2899708-1-sathyanarayanan.kuppuswamy@linux.intel.com>
 <20210804181329.2899708-9-sathyanarayanan.kuppuswamy@linux.intel.com>
 <YSUaAQPiBUqubBHM@zn.tnic> <YSUnDQUrGYc8aY9j@google.com>
 <YSUsBVx2DD7MCyn/@zn.tnic>
From:   "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@linux.intel.com>
Message-ID: <0d2421ac-c501-d33f-d3fc-be9dac7e221c@linux.intel.com>
Date:   Tue, 31 Aug 2021 13:49:54 -0700
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Hi Boris,

On 8/24/21 10:27 AM, Borislav Petkov wrote:
> I think in the next version all those _tdx_hypercall() wrappers should
> spell it out what the parameters they pass are used for.
> 
> Hohumm.

Regarding details about _tdx_hypercall() wrapper usage, do you want me
to document the ABI details?

For example for MSR read,

static u64 tdx_read_msr_safe(unsigned int msr, int *err)
{
         struct tdx_hypercall_output out = {0};
         u64 ret;

         WARN_ON_ONCE(tdx_is_context_switched_msr(msr));

         /*
          * TDX MSR READ Hypercall ABI:
          *
          * Input Registers:
          *
          * R11(EXIT_REASON_MSR_READ) - hypercall sub function id
          * R12(msr) - MSR index
          *
          * Output Registers:
          *
          * R10(out.r10) - Hypercall return error code
          * R11(out.r11) - MSR read value
          * RAX(ret) - TDCALL error code
          */
         ret = _tdx_hypercall(EXIT_REASON_MSR_READ, msr, 0, 0, 0, &out);

Let me know if you agree with above format?

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer