linux-kernel - Re: [PATCH v7 05/10] x86/tdx: Handle port I/O

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Message-ID: <87v91v2zkk.ffs@tglx>
Date:   Sun, 17 Oct 2021 21:58:35 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, Paolo Bonzini <pbonzini@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     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>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 05/10] x86/tdx: Handle port I/O

On Tue, Oct 05 2021 at 13:41, Kuppuswamy Sathyanarayanan wrote:
>  									\
>  static inline void outs##bwl(int port, const void *addr, unsigned long count) \
>  {									\
> -	if (sev_key_active()) {						\
> +	if (sev_key_active() ||						\
> +	    cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO)) {		\

Instead of adding an extra check, can you please replace that
sev_key_active() with cc_platform_has() completely?

> +/*
> + * tdx_handle_early_io() cannot be re-used in #VE handler for handling
> + * I/O because the way of handling string I/O is different between
> + * normal and early I/O case. Also, once trace support is enabled,
> + * tdx_handle_io() will be extended to use trace calls which is also
> + * not valid for early I/O cases.
> + */
> +static void tdx_handle_io(struct pt_regs *regs, u32 exit_qual)
> +{
> +	struct tdx_hypercall_output outh;
> +	int out, size, port, ret;
> +	bool string;
> +	u64 mask;
> +
> +	string = VE_IS_IO_STRING(exit_qual);
> +
> +	/* I/O strings ops are unrolled at build time. */

Fancy. The compiler can evaluate sev_key_active() and
cc_platform_has() at build time?

Thanks,

        tglx