linux-kernel - Re: [PATCHv6 10/30] x86/tdx: Handle CPUID via #VE

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Date:   Thu, 17 Mar 2022 12:32:07 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...el.com,
        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,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCHv6 10/30] x86/tdx: Handle CPUID via #VE

On Wed, Mar 16 2022 at 05:08, Kirill A. Shutemov wrote:
> In TDX guests, most CPUID leaf/sub-leaf combinations are virtualized
> by the TDX module while some trigger #VE.
>
> Implement the #VE handling for EXIT_REASON_CPUID by handing it through
> the hypercall, which in turn lets the TDX module handle it by invoking
> the host VMM.
>
> More details on CPUID Virtualization can be found in the TDX module
> specification, the section titled "CPUID Virtualization".
>
> Note that VMM that handles the hypercall is not trusted. It can return
> data that may steer the guest kernel in wrong direct. Only allow  VMM
> to control range reserved for hypervisor communication.
>
> Return all-zeros for any CPUID outside the hypervisor range. It matches
> CPU behaviour for non-supported leaf.
>
> Co-developed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> Reviewed-by: Andi Kleen <ak@...ux.intel.com>
> Reviewed-by: Tony Luck <tony.luck@...el.com>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Reviewed-by: Dave Hansen <dave.hansen@...ux.intel.com>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>