linux-kernel - Re: [PATCHv4 16/30] x86/boot/compressed: Support TDX guest port I/O at decompression time

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Message-ID: <10b4cfef-49f8-12db-0ad7-2a6acad00234@intel.com>
Date:   Thu, 24 Feb 2022 14:22:36 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        luto@...nel.org, peterz@...radead.org
Cc:     sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
        ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
        hpa@...or.com, jgross@...e.com, jmattson@...gle.com,
        joro@...tes.org, jpoimboe@...hat.com, knsathya@...nel.org,
        pbonzini@...hat.com, sdeep@...are.com, seanjc@...gle.com,
        tony.luck@...el.com, vkuznets@...hat.com, wanpengli@...cent.com,
        thomas.lendacky@....com, brijesh.singh@....com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4 16/30] x86/boot/compressed: Support TDX guest port I/O
 at decompression time

On 2/24/22 07:56, Kirill A. Shutemov wrote:
> @@ -24,4 +88,11 @@ void early_tdx_detect(void)
>  
>  	/* Cache TDX guest feature status */
>  	tdx_guest_detected = true;
> +
> +	pio_ops.inb = tdx_inb;
> +	pio_ops.inw = tdx_inw;
> +	pio_ops.inl = tdx_inl;
> +	pio_ops.outb = tdx_outb;
> +	pio_ops.outw = tdx_outw;
> +	pio_ops.outl = tdx_outl;
>  }

I guess the kernel isn't going to get far if any of this goes wrong.
But, I do kinda wish that code ^^ was connected to the below code somehow:

> +static inline void init_io_ops(void)
> +{
> +	pio_ops.inb = inb;
> +	pio_ops.inw = inw;
> +	pio_ops.inl = inl;
> +	pio_ops.outb = outb;
> +	pio_ops.outw = outw;
> +	pio_ops.outl = outl;
> +}

Maybe just a comment would do it.  Or, maybe init_io_ops() should  just
be called init_default_io_ops().  I think this would do:

	/*
	 * Use the normal I/O instructions by default.
	 * TDX guests override these to use hypercalls.
	 */

if it went in init_io_ops() from the last patch.

> 
> +static inline unsigned int tdx_io_in(int size, u16 port)
> +{
> +	struct tdx_hypercall_args args = {
> +		.r10 = TDX_HYPERCALL_STANDARD,
> +		.r11 = EXIT_REASON_IO_INSTRUCTION,
> +		.r12 = size,
> +		.r13  = 0,

		    ^ munged whitespace?

> +		.r14 = port,
> +	};
> +
> +	if (__tdx_hypercall(&args, TDX_HCALL_HAS_OUTPUT))
> +		return UINT_MAX;
> +
> +	return args.r11;
> +}

With that fixed:

Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>