[v2] x86/tdx: Adjust TD settings on boot

[PATCHv2 4/4] x86/tdx: Enable ENUM_TOPOLOGY

Posted by Kirill A. Shutemov 1 year, 10 months ago

TDX 1.0 defines baseline behaviour of TDX guest platform. In 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
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@linux.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
 
 /* TDCS_TDX_FEATURES0 bits */
 #define TDX_FEATURES0_PENDING_EPT_VIOLATION_V2	BIT_ULL(16)
+#define TDX_FEATURES0_ENUM_TOPOLOGY		BIT_ULL(20)
 
 /* TDCS_CONFIG_FLAGS bits */
 #define TDCS_CONFIG_FLEXIBLE_PENDING_VE	BIT_ULL(1)
 
 /* TDCS_TD_CTLS bits */
 #define TD_CTLS_PENDING_VE_DISABLE	BIT_ULL(0)
+#define TD_CTLS_ENUM_TOPOLOGY		BIT_ULL(1)
 
 /* TDX hypercall Leaf IDs */
 #define TDVMCALL_MAP_GPA		0x10001
-- 
2.43.0

Re: [PATCHv2 4/4] x86/tdx: Enable ENUM_TOPOLOGY

Posted by Dave Hansen 1 year, 9 months ago

On 3/25/24 03:46, Kirill A. Shutemov wrote:
> +	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");
> +	}

This is looking pretty familiar at this point.

I'd almost rather just have it do a plain old:

	tdcs_ctls_set(TD_CTLS_ENUM_TOPOLOGY);

... and leave it at that.

*If* there is a generic return code for "invalid" as opposed to a
not-supported tdcs_ctls_set(), then it's arguable that you can spit out
a message for an unexpected "invalid" error.

But seriously, why all the complexity over and over?  What does this buy?

Re: [PATCHv2 4/4] x86/tdx: Enable ENUM_TOPOLOGY

Posted by Kirill A. Shutemov 1 year, 9 months ago

On Wed, Apr 24, 2024 at 03:20:54PM -0700, Dave Hansen wrote:
> But seriously, why all the complexity over and over?  What does this buy?

Thanks. That's a good perspective. I will rework the patchset dropping all
unneeded enumeration.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

Re: [PATCHv2 4/4] x86/tdx: Enable ENUM_TOPOLOGY

Posted by Huang, Kai 1 year, 10 months ago

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@linux.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.

Re: [PATCHv2 4/4] x86/tdx: Enable ENUM_TOPOLOGY

Posted by kirill.shutemov@linux.intel.com 1 year, 10 months ago

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@linux.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