linux-kernel - Re: [PATCH v3 06/10] x86/hyperv: Introduce a global variable hyperv_paravisor

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Message-ID: <90bc229b-133d-f695-4459-3fad557a8fe2@gmail.com>
Date:   Thu, 24 Aug 2023 22:41:53 +0800
From:   Tianyu Lan <ltykernel@...il.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@...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 06/10] x86/hyperv: Introduce a global variable
 hyperv_paravisor_present

On 8/24/2023 4:07 PM, Dexuan Cui wrote:
> The new variable hyperv_paravisor_present is set only when the VM
> is a SNP/TDX VM with the paravisor running: see ms_hyperv_init_platform().
> 
> We introduce hyperv_paravisor_present because we can not use
> ms_hyperv.paravisor_present in arch/x86/include/asm/mshyperv.h:
> 
> struct ms_hyperv_info is defined in include/asm-generic/mshyperv.h, which
> is included at the end of arch/x86/include/asm/mshyperv.h, but at the
> beginning of arch/x86/include/asm/mshyperv.h, we would already need to use
> struct ms_hyperv_info in hv_do_hypercall().
> 
> We use hyperv_paravisor_present only in include/asm-generic/mshyperv.h,
> and use ms_hyperv.paravisor_present elsewhere. In the future, we'll
> introduce a hypercall function structure for different VM types, and
> at boot time, the right function pointers would be written into the
> structure so that runtime testing of TDX vs. SNP vs. normal will be
> avoided and hyperv_paravisor_present will no longer be needed.
> 
> Call hv_vtom_init() when it's a VBS VM or when ms_hyperv.paravisor_present
> is true, i.e. the VM is a SNP VM or TDX VM with the paravisor.
> 
> Enhance hv_vtom_init() for a TDX VM with the paravisor.
> 
> In hv_common_cpu_init(), don't decrypt the hyperv_pcpu_input_arg
> for a TDX VM with the paravisor, just like we don't decrypt the page
> for a SNP VM with the paravisor.
> 
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>

Reviewed-by: Tianyu Lan <tiala@...rosoft.com>