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

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Date: Tue, 26 Mar 2024 14:21:24 +0200
From: "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
To: "Huang, Kai" <kai.huang@...el.com>
Cc: "tglx@...utronix.de" <tglx@...utronix.de>, 
	"mingo@...hat.com" <mingo@...hat.com>, "Hansen, Dave" <dave.hansen@...el.com>, 
	"bp@...en8.de" <bp@...en8.de>, 
	"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 Tue, Mar 26, 2024 at 10:59:38AM +0000, Huang, Kai wrote:
> 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
> 

Okay.

> > 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.

See "Intel TDX Module v1.5 ABI Definitions":

https://cdrdv2.intel.com/v1/dl/getContent/795381

It has all fields described in JSON.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov