linux-kernel - Re: [PATCHv2 4/4] x86/tdx: Enable ENUM

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Message-ID: <ea00b63e4e7f27dfb35b8b5947bd0951039db9bd.camel@intel.com>
Date: Tue, 26 Mar 2024 10:59:38 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>, "mingo@...hat.com"
	<mingo@...hat.com>, "Hansen, Dave" <dave.hansen@...el.com>, "bp@...en8.de"
	<bp@...en8.de>
CC: "sathyanarayanan.kuppuswamy@...ux.intel.com"
	<sathyanarayanan.kuppuswamy@...ux.intel.com>, "hpa@...or.com"
	<hpa@...or.com>, "Reshetova, Elena" <elena.reshetova@...el.com>,
	"seanjc@...gle.com" <seanjc@...gle.com>, "Edgecombe, Rick P"
	<rick.p.edgecombe@...el.com>, "x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2 4/4] x86/tdx: Enable ENUM_TOPOLOGY

On Mon, 2024-03-25 at 12:46 +0200, Kirill A. Shutemov wrote:
> TDX 1.0 defines baseline behaviour of TDX guest platform. In TDX 1.0

							    ^ Not needed.

> generates a #VE when accessing topology-related CPUID leafs (0xB and
> 0x1F) and the X2APIC_APICID MSR. The kernel returns all zeros on CPUID
> topology. Any complications will cause problems.
> 
> The ENUM_TOPOLOGY feature allows the VMM to provide topology
> information to the guest. Enabling the feature eliminates
> topology-related #VEs: the TDX module virtualizes accesses to
> the CPUID leafs and the MSR.
> 
> Enable ENUM_TOPOLOGY if it is available.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>  arch/x86/coco/tdx/tdx.c           | 19 +++++++++++++++++++
>  arch/x86/include/asm/shared/tdx.h |  3 +++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index 860bfdd5a11d..b2d969432a22 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -289,6 +289,25 @@ static void tdx_setup(u64 *cc_mask)
>  		else
>  			tdx_panic(msg);
>  	}
> +
> +	/*
> +	 * TDX 1.0 generates a #VE when accessing topology-related CPUID leafs
> +	 * (0xB and 0x1F) and the X2APIC_APICID MSR. The kernel returns all
> +	 * zeros on CPUID #VEs. In practice, this means that the kernel can only
> +	 * boot with a plain topology. Any complications will cause problems.
> +	 *
> +	 * The ENUM_TOPOLOGY feature allows the VMM to provide topology
> +	 * information to the guest in a safe manner. Enabling the feature
> +	 * eliminates topology-related #VEs: the TDX module virtualizes
> +	 * accesses to the CPUID leafs and the MSR.
> +	 *
> +	 * Enable ENUM_TOPOLOGY if it is available.
> +	 */
> +	if ((features & TDX_FEATURES0_ENUM_TOPOLOGY) &&
> +	    tdg_vm_rd(TDCS_TOPOLOGY_ENUM_CONFIGURED)) {
> +		if (!tdcs_ctls_set(TD_CTLS_ENUM_TOPOLOGY))
> +			pr_warn("Failed to enable ENUM_TOPOLOGY\n");
> +	}
>  }
>  
>  /*
> diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
> index 29a61c72e4dd..2964c506b241 100644
> --- a/arch/x86/include/asm/shared/tdx.h
> +++ b/arch/x86/include/asm/shared/tdx.h
> @@ -27,15 +27,18 @@
>  #define TDCS_CONFIG_FLAGS		0x1110000300000016
>  #define TDCS_TD_CTLS			0x1110000300000017
>  #define TDCS_NOTIFY_ENABLES		0x9100000000000010
> +#define TDCS_TOPOLOGY_ENUM_CONFIGURED	0x9100000000000019

Do you know where can I find the metadata field ID definition?

It seems I couldn't find all metadata field ID definitions in the latest TDX 1.5
ABI spec anymore.