linux-kernel - Re: [PATCH v3 08/10] x86/hyperv: Use TDX GHCI to access some MSRs in a TDX VM with the paravisor

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Date:   Mon, 4 Dec 2023 07:10:29 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Dexuan Cui <decui@...rosoft.com>, ak@...ux.intel.com,
        arnd@...db.de, bp@...en8.de, brijesh.singh@....com,
        dan.j.williams@...el.com, dave.hansen@...ux.intel.com,
        haiyangz@...rosoft.com, hpa@...or.com, jane.chu@...cle.com,
        kirill.shutemov@...ux.intel.com, kys@...rosoft.com,
        linux-hyperv@...r.kernel.org, luto@...nel.org, mingo@...hat.com,
        peterz@...radead.org, rostedt@...dmis.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, seanjc@...gle.com,
        tglx@...utronix.de, tony.luck@...el.com, wei.liu@...nel.org,
        Jason@...c4.com, nik.borisov@...e.com, mikelley@...rosoft.com
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, Tianyu.Lan@...rosoft.com,
        rick.p.edgecombe@...el.com, andavis@...hat.com, mheslin@...hat.com,
        vkuznets@...hat.com, xiaoyao.li@...el.com
Subject: Re: [PATCH v3 08/10] x86/hyperv: Use TDX GHCI to access some MSRs in
 a TDX VM with the paravisor

On 8/24/23 01:07, Dexuan Cui wrote:
> +#ifdef CONFIG_INTEL_TDX_GUEST
> +static void hv_tdx_msr_write(u64 msr, u64 val)
> +{
> +	struct tdx_hypercall_args args = {
> +		.r10 = TDX_HYPERCALL_STANDARD,
> +		.r11 = EXIT_REASON_MSR_WRITE,
> +		.r12 = msr,
> +		.r13 = val,
> +	};
> +
> +	u64 ret = __tdx_hypercall(&args);
> +
> +	WARN_ONCE(ret, "Failed to emulate MSR write: %lld\n", ret);
> +}

First of all, I'd really appreciate if you could seek out explicit acks
for this kind of stuff before merging it.  This surprised me.

Can you please merge these generic things back into the main TDX code?
There's nothing Hyper-V specific about any of this code.  Basically, you
can make a hv_tdx_whatever() variant, but make _that_ in the generic TDX
code and then export only _that_.