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

[Kuppuswamy, Sathyanarayanan]

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