[PATCHv2 0/4] x86/tdx: Adjust TD settings on boot

[PATCHv2 0/4] x86/tdx: Adjust TD settings on boot

[Kirill A. Shutemov]

Adjust TD setting on boot:

  - Disable EPT violation #VE on private memory if TD can
    control it;

  - Enable virtualization of topology-related CPUID leafs
    X2APIC_APICID MSR;

v2:
  - Rebased;
  - Allow write to TDCS_TD_CTLS to fail;
  - Adjust commit messages;

Kirill A. Shutemov (4):
  x86/tdx: Introduce tdg_vm_wr()
  x86/tdx: Rename tdx_parse_tdinfo() to tdx_setup()
  x86/tdx: Handle PENDING_EPT_VIOLATION_V2
  x86/tdx: Enable ENUM_TOPOLOGY

 arch/x86/coco/tdx/tdx.c           | 125 ++++++++++++++++++++++++++----
 arch/x86/include/asm/shared/tdx.h |  21 ++++-
 2 files changed, 131 insertions(+), 15 deletions(-)

-- 
2.43.0

[PATCHv2 1/4] x86/tdx: Introduce tdg_vm_wr()

[Kirill A. Shutemov]

Add a helper function to write to a TD-scope metadata field and use it
to set NOTIFY_ENABLES.

The helper function will be paired with tdg_vm_rd() and will be used to
manipulate other metadata fields, not just NOTIFY_ENABLES.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/coco/tdx/tdx.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 59776ce1c1d7..4fb36e5c4e80 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -77,6 +77,20 @@ static inline void tdcall(u64 fn, struct tdx_module_args *args)
 		panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);
 }
 
+static inline u64 tdg_vm_wr(u64 field, u64 value, u64 mask)
+{
+	struct tdx_module_args args = {
+		.rdx = field,
+		.r8 = value,
+		.r9 = mask,
+	};
+
+	tdcall(TDG_VM_WR, &args);
+
+	/* Old value */
+	return args.r8;
+}
+
 /**
  * tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT
  *                           subtype 0) using TDG.MR.REPORT TDCALL.
@@ -902,10 +916,6 @@ static void tdx_kexec_unshare_mem(void)
 
 void __init tdx_early_init(void)
 {
-	struct tdx_module_args args = {
-		.rdx = TDCS_NOTIFY_ENABLES,
-		.r9 = -1ULL,
-	};
 	u64 cc_mask;
 	u32 eax, sig[3];
 
@@ -924,7 +934,7 @@ void __init tdx_early_init(void)
 	cc_set_mask(cc_mask);
 
 	/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
-	tdcall(TDG_VM_WR, &args);
+	tdg_vm_wr(TDCS_NOTIFY_ENABLES, 0, -1ULL);
 
 	/*
 	 * All bits above GPA width are reserved and kernel treats shared bit
-- 
2.43.0

Re: [PATCHv2 1/4] x86/tdx: Introduce tdg_vm_wr()

[Huang, Kai]

On Mon, 2024-03-25 at 12:46 +0200, Kirill A. Shutemov wrote:
> Add a helper function to write to a TD-scope metadata field and use it
> to set NOTIFY_ENABLES.
> 
> The helper function will be paired with tdg_vm_rd() and will be used to
> manipulate other metadata fields, not just NOTIFY_ENABLES.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> 

Reviewed-by: Kai Huang <kai.huang@intel.com>

Re: [PATCHv2 1/4] x86/tdx: Introduce tdg_vm_wr()

[Kuppuswamy Sathyanarayanan]

On 3/25/24 3:46 AM, Kirill A. Shutemov wrote:
> Add a helper function to write to a TD-scope metadata field and use it
> to set NOTIFY_ENABLES.
>
> The helper function will be paired with tdg_vm_rd() and will be used to
> manipulate other metadata fields, not just NOTIFY_ENABLES.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> ---

Looks good to me.

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

>  arch/x86/coco/tdx/tdx.c | 20 +++++++++++++++-----
>  1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index 59776ce1c1d7..4fb36e5c4e80 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -77,6 +77,20 @@ static inline void tdcall(u64 fn, struct tdx_module_args *args)
>  		panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);
>  }
>  
> +static inline u64 tdg_vm_wr(u64 field, u64 value, u64 mask)
> +{
> +	struct tdx_module_args args = {
> +		.rdx = field,
> +		.r8 = value,
> +		.r9 = mask,
> +	};
> +
> +	tdcall(TDG_VM_WR, &args);
> +
> +	/* Old value */
> +	return args.r8;
> +}
> +
>  /**
>   * tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT
>   *                           subtype 0) using TDG.MR.REPORT TDCALL.
> @@ -902,10 +916,6 @@ static void tdx_kexec_unshare_mem(void)
>  
>  void __init tdx_early_init(void)
>  {
> -	struct tdx_module_args args = {
> -		.rdx = TDCS_NOTIFY_ENABLES,
> -		.r9 = -1ULL,
> -	};
>  	u64 cc_mask;
>  	u32 eax, sig[3];
>  
> @@ -924,7 +934,7 @@ void __init tdx_early_init(void)
>  	cc_set_mask(cc_mask);
>  
>  	/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
> -	tdcall(TDG_VM_WR, &args);
> +	tdg_vm_wr(TDCS_NOTIFY_ENABLES, 0, -1ULL);
>  
>  	/*
>  	 * All bits above GPA width are reserved and kernel treats shared bit

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer

Re: [PATCHv2 1/4] x86/tdx: Introduce tdg_vm_wr()

[Dave Hansen]

So, the text here should help me understand what is going on.  What it
tries to tell me should not be a literal rephrasing of the contents of
the diff.

This patch literally introduces a function called tdg_vm_wr().  The
subject adds precisely zero to what I can get from reading the diff.

How about:

	x86/tdx: Factor out TD metadata write tdcall

On 3/25/24 03:46, Kirill A. Shutemov wrote:
> Add a helper function to write to a TD-scope metadata field and use it
> to set NOTIFY_ENABLES.
> 
> The helper function will be paired with tdg_vm_rd() and will be used to
> manipulate other metadata fields, not just NOTIFY_ENABLES.

Ideally this would at least tell me what problem this is solving:

	The TDG_VM_WR seamcall is used to ask the TDX module to change
	some TD-specific VM configuration.  There is currently only one
	user in the kernel of this seamcall.  More will be added
	shortly.

... and then the solution:

	Refactor to make way for more users of TDG_VM_WR who will need
	to modify other TD configuration values.

> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index 59776ce1c1d7..4fb36e5c4e80 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -77,6 +77,20 @@ static inline void tdcall(u64 fn, struct tdx_module_args *args)
>  		panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);
>  }
>  
> +static inline u64 tdg_vm_wr(u64 field, u64 value, u64 mask)
> +{
> +	struct tdx_module_args args = {
> +		.rdx = field,
> +		.r8 = value,
> +		.r9 = mask,
> +	};
> +
> +	tdcall(TDG_VM_WR, &args);
> +
> +	/* Old value */
> +	return args.r8;
> +}
> +
>  /**
>   * tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT
>   *                           subtype 0) using TDG.MR.REPORT TDCALL.
> @@ -902,10 +916,6 @@ static void tdx_kexec_unshare_mem(void)
>  
>  void __init tdx_early_init(void)
>  {
> -	struct tdx_module_args args = {
> -		.rdx = TDCS_NOTIFY_ENABLES,
> -		.r9 = -1ULL,
> -	};
>  	u64 cc_mask;
>  	u32 eax, sig[3];
>  
> @@ -924,7 +934,7 @@ void __init tdx_early_init(void)
>  	cc_set_mask(cc_mask);
>  
>  	/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
> -	tdcall(TDG_VM_WR, &args);
> +	tdg_vm_wr(TDCS_NOTIFY_ENABLES, 0, -1ULL);
>  
>  	/*
>  	 * All bits above GPA width are reserved and kernel treats shared bit

[PATCHv2 2/4] x86/tdx: Rename tdx_parse_tdinfo() to tdx_setup()

[Kirill A. Shutemov]

Rename tdx_parse_tdinfo() to tdx_setup() and move setting NOTIFY_ENABLES
there.

The function will be extended to adjust TD configuration.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---
 arch/x86/coco/tdx/tdx.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 4fb36e5c4e80..08e2bb462ce8 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -181,7 +181,7 @@ static void __noreturn tdx_panic(const char *msg)
 		__tdx_hypercall(&args);
 }
 
-static void tdx_parse_tdinfo(u64 *cc_mask)
+static void tdx_setup(u64 *cc_mask)
 {
 	struct tdx_module_args args = {};
 	unsigned int gpa_width;
@@ -206,6 +206,9 @@ static void tdx_parse_tdinfo(u64 *cc_mask)
 	gpa_width = args.rcx & GENMASK(5, 0);
 	*cc_mask = BIT_ULL(gpa_width - 1);
 
+	/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
+	tdg_vm_wr(TDCS_NOTIFY_ENABLES, 0, -1ULL);
+
 	/*
 	 * The kernel can not handle #VE's when accessing normal kernel
 	 * memory.  Ensure that no #VE will be delivered for accesses to
@@ -930,11 +933,11 @@ void __init tdx_early_init(void)
 	setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
 
 	cc_vendor = CC_VENDOR_INTEL;
-	tdx_parse_tdinfo(&cc_mask);
-	cc_set_mask(cc_mask);
 
-	/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
-	tdg_vm_wr(TDCS_NOTIFY_ENABLES, 0, -1ULL);
+	/* Configure the TD */
+	tdx_setup(&cc_mask);
+
+	cc_set_mask(cc_mask);
 
 	/*
 	 * All bits above GPA width are reserved and kernel treats shared bit
-- 
2.43.0

Re: [PATCHv2 2/4] x86/tdx: Rename tdx_parse_tdinfo() to tdx_setup()

[Huang, Kai]

On Mon, 2024-03-25 at 12:46 +0200, Kirill A. Shutemov wrote:
> Rename tdx_parse_tdinfo() to tdx_setup() and move setting NOTIFY_ENABLES
> there.
> 
> The function will be extended to adjust TD configuration.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> 

Reviewed-by: Kai Huang <kai.huang@intel.com>

[PATCHv2 3/4] x86/tdx: Handle PENDING_EPT_VIOLATION_V2

[Kirill A. Shutemov]

PENDING_EPT_VIOLATION_V2 allows TD to control whether access to
a pending page triggers #VE.

Kernel doesn't want to see any #VEs on accesses to private memory:
disable such #VEs.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/coco/tdx/tdx.c           | 75 ++++++++++++++++++++++++++++---
 arch/x86/include/asm/shared/tdx.h | 18 +++++++-
 2 files changed, 87 insertions(+), 6 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 08e2bb462ce8..860bfdd5a11d 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -77,6 +77,17 @@ static inline void tdcall(u64 fn, struct tdx_module_args *args)
 		panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);
 }
 
+static inline u64 tdg_vm_rd(u64 field)
+{
+	struct tdx_module_args args = {
+		.rdx = field,
+	};
+
+	tdcall(TDG_VM_RD, &args);
+
+	return args.r8;
+}
+
 static inline u64 tdg_vm_wr(u64 field, u64 value, u64 mask)
 {
 	struct tdx_module_args args = {
@@ -91,6 +102,28 @@ static inline u64 tdg_vm_wr(u64 field, u64 value, u64 mask)
 	return args.r8;
 }
 
+static inline u64 tdg_sys_rd(u64 field)
+{
+	struct tdx_module_args args = {
+		.rdx = field,
+	};
+
+	tdcall(TDG_SYS_RD, &args);
+
+	return args.r8;
+}
+
+static bool tdcs_ctls_set(u64 mask)
+{
+	struct tdx_module_args args = {
+		.rdx = TDCS_TD_CTLS,
+		.r8 = mask,
+		.r9 = mask,
+	};
+
+	return __tdcall(TDG_VM_WR, &args) == TDX_SUCCESS;
+}
+
 /**
  * tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT
  *                           subtype 0) using TDG.MR.REPORT TDCALL.
@@ -185,7 +218,8 @@ static void tdx_setup(u64 *cc_mask)
 {
 	struct tdx_module_args args = {};
 	unsigned int gpa_width;
-	u64 td_attr;
+	u64 td_attr, features;
+	bool sept_ve_disabled;
 
 	/*
 	 * TDINFO TDX module call is used to get the TD execution environment
@@ -206,19 +240,50 @@ static void tdx_setup(u64 *cc_mask)
 	gpa_width = args.rcx & GENMASK(5, 0);
 	*cc_mask = BIT_ULL(gpa_width - 1);
 
+	td_attr = args.rdx;
+
 	/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
 	tdg_vm_wr(TDCS_NOTIFY_ENABLES, 0, -1ULL);
 
+	features = tdg_sys_rd(TDCS_TDX_FEATURES0);
+
 	/*
 	 * The kernel can not handle #VE's when accessing normal kernel
 	 * memory.  Ensure that no #VE will be delivered for accesses to
 	 * TD-private memory.  Only VMM-shared memory (MMIO) will #VE.
+	 *
+	 * Check if the TD is created with SEPT #VE disabled.
 	 */
-	td_attr = args.rdx;
-	if (!(td_attr & ATTR_SEPT_VE_DISABLE)) {
-		const char *msg = "TD misconfiguration: SEPT_VE_DISABLE attribute must be set.";
+	sept_ve_disabled = td_attr & ATTR_SEPT_VE_DISABLE;
 
-		/* Relax SEPT_VE_DISABLE check for debug TD. */
+	/*
+	 * Check if flexible control of SEPT #VE is supported.
+	 *
+	 * The check consists of verifying if the feature is supported by the
+	 * TDX module (the TDX_FEATURES0 check) and if the feature is enabled
+	 * for this TD (CONFIG_FLAGS check).
+	 *
+	 * If flexible control is supported, disable SEPT #VE.
+	 *
+	 * Disable SEPT #VE regardless of ATTR_SEPT_VE_DISABLE status as
+	 * flexible control allows software running before the kernel to
+	 * enable it.
+	 *
+	 * Skip SEPT disabling for debug TD. SEPT #VE is unsafe but can be
+	 * useful for debugging to produce a stack trace. Known to be useful
+	 * for debugging unaccepted memory problems.
+	 */
+	if (features & TDX_FEATURES0_PENDING_EPT_VIOLATION_V2 &&
+	    (tdg_vm_rd(TDCS_CONFIG_FLAGS) & TDCS_CONFIG_FLEXIBLE_PENDING_VE) &&
+	    !(td_attr & ATTR_DEBUG)) {
+		if (tdcs_ctls_set(TD_CTLS_PENDING_VE_DISABLE))
+			sept_ve_disabled = true;
+	}
+
+	if (!sept_ve_disabled) {
+		const char *msg = "TD misconfiguration: SEPT #VE has to be disabled";
+
+		/* Relax SEPT #VE disable check for debug TD. */
 		if (td_attr & ATTR_DEBUG)
 			pr_warn("%s\n", msg);
 		else
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index fdfd41511b02..29a61c72e4dd 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -16,11 +16,27 @@
 #define TDG_VP_VEINFO_GET		3
 #define TDG_MR_REPORT			4
 #define TDG_MEM_PAGE_ACCEPT		6
+#define TDG_VM_RD			7
 #define TDG_VM_WR			8
+#define TDG_SYS_RD			11
 
-/* TDCS fields. To be used by TDG.VM.WR and TDG.VM.RD module calls */
+/* TDX Global Metadata. To be used by TDG.SYS.RD */
+#define TDCS_TDX_FEATURES0		0x0A00000300000008
+
+/* TDX TD-Scope Metadata. To be used by TDG.VM.WR and TDG.VM.RD */
+#define TDCS_CONFIG_FLAGS		0x1110000300000016
+#define TDCS_TD_CTLS			0x1110000300000017
 #define TDCS_NOTIFY_ENABLES		0x9100000000000010
 
+/* TDCS_TDX_FEATURES0 bits */
+#define TDX_FEATURES0_PENDING_EPT_VIOLATION_V2	BIT_ULL(16)
+
+/* 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)
+
 /* TDX hypercall Leaf IDs */
 #define TDVMCALL_MAP_GPA		0x10001
 #define TDVMCALL_GET_QUOTE		0x10002
-- 
2.43.0

Re: [PATCHv2 3/4] x86/tdx: Handle PENDING_EPT_VIOLATION_V2

[Dave Hansen]

On 3/25/24 03:46, Kirill A. Shutemov wrote:
> PENDING_EPT_VIOLATION_V2 allows TD to control whether access to
> a pending page triggers #VE.
> 
> Kernel doesn't want to see any #VEs on accesses to private memory:
> disable such #VEs.

This is really a bare bones changelog.  The connection between "pending"
and "private" goes unmentioned.  It's not obvious when the kernel might
be exposed to one of these #VE's.

> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index 08e2bb462ce8..860bfdd5a11d 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -77,6 +77,17 @@ static inline void tdcall(u64 fn, struct tdx_module_args *args)
>  		panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);
>  }
>  
> +static inline u64 tdg_vm_rd(u64 field)
> +{
> +	struct tdx_module_args args = {
> +		.rdx = field,
> +	};
> +
> +	tdcall(TDG_VM_RD, &args);
> +
> +	return args.r8;
> +}
> +
>  static inline u64 tdg_vm_wr(u64 field, u64 value, u64 mask)
>  {
>  	struct tdx_module_args args = {
> @@ -91,6 +102,28 @@ static inline u64 tdg_vm_wr(u64 field, u64 value, u64 mask)
>  	return args.r8;
>  }
>  
> +static inline u64 tdg_sys_rd(u64 field)
> +{
> +	struct tdx_module_args args = {
> +		.rdx = field,
> +	};
> +
> +	tdcall(TDG_SYS_RD, &args);
> +
> +	return args.r8;
> +}

I scratched my head for a minute on why these two identical functions
were introduced.  Then I realized that they're different TDCALLs.

Please break them out into a separate patch where you can mention this.
Also, the least we can do is a one-line comment about what they do:

/* Read metadata about how *this* VM is configured. */
static inline u64 tdg_vm_rd(u64 field)
...

/* Read metadata about the TDX system as whole. */
static inline u64 tdg_sys_rd(u64 field)

> +static bool tdcs_ctls_set(u64 mask)
> +{
> +	struct tdx_module_args args = {
> +		.rdx = TDCS_TD_CTLS,
> +		.r8 = mask,
> +		.r9 = mask,
> +	};
> +
> +	return __tdcall(TDG_VM_WR, &args) == TDX_SUCCESS;
> +}

This is acronym soup.  It's made worse by "TDCS_TD_CTLS" being
ungoogleable and not literally present in the first three TDX PDFs that
I dug in.

It's also not clear logically how this differs from tdg_vm_wr().

>  /**
>   * tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT
>   *                           subtype 0) using TDG.MR.REPORT TDCALL.
> @@ -185,7 +218,8 @@ static void tdx_setup(u64 *cc_mask)
>  {
>  	struct tdx_module_args args = {};
>  	unsigned int gpa_width;
> -	u64 td_attr;
> +	u64 td_attr, features;
> +	bool sept_ve_disabled;
>  
>  	/*
>  	 * TDINFO TDX module call is used to get the TD execution environment
> @@ -206,19 +240,50 @@ static void tdx_setup(u64 *cc_mask)
>  	gpa_width = args.rcx & GENMASK(5, 0);
>  	*cc_mask = BIT_ULL(gpa_width - 1);
>  
> +	td_attr = args.rdx;
> +
>  	/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
>  	tdg_vm_wr(TDCS_NOTIFY_ENABLES, 0, -1ULL);
>  
> +	features = tdg_sys_rd(TDCS_TDX_FEATURES0);
> +
>  	/*
>  	 * The kernel can not handle #VE's when accessing normal kernel
>  	 * memory.  Ensure that no #VE will be delivered for accesses to
>  	 * TD-private memory.  Only VMM-shared memory (MMIO) will #VE.
> +	 *
> +	 * Check if the TD is created with SEPT #VE disabled.
>  	 */
> -	td_attr = args.rdx;
> -	if (!(td_attr & ATTR_SEPT_VE_DISABLE)) {
> -		const char *msg = "TD misconfiguration: SEPT_VE_DISABLE attribute must be set.";
> +	sept_ve_disabled = td_attr & ATTR_SEPT_VE_DISABLE;
>  
> -		/* Relax SEPT_VE_DISABLE check for debug TD. */
> +	/*
> +	 * Check if flexible control of SEPT #VE is supported.
> +	 *
> +	 * The check consists of verifying if the feature is supported by the
> +	 * TDX module (the TDX_FEATURES0 check) and if the feature is enabled
> +	 * for this TD (CONFIG_FLAGS check).
> +	 *
> +	 * If flexible control is supported, disable SEPT #VE.
> +	 *
> +	 * Disable SEPT #VE regardless of ATTR_SEPT_VE_DISABLE status as
> +	 * flexible control allows software running before the kernel to
> +	 * enable it.
> +	 *
> +	 * Skip SEPT disabling for debug TD. SEPT #VE is unsafe but can be
> +	 * useful for debugging to produce a stack trace. Known to be useful
> +	 * for debugging unaccepted memory problems.
> +	 */
> +	if (features & TDX_FEATURES0_PENDING_EPT_VIOLATION_V2 &&
> +	    (tdg_vm_rd(TDCS_CONFIG_FLAGS) & TDCS_CONFIG_FLEXIBLE_PENDING_VE) &&

Can't we just check TDCS_CONFIG_FLEXIBLE_PENDING_VE alone?  Surely that
flag can't get set if !TDX_FEATURES0_PENDING_EPT_VIOLATION_V2.

In any case, this is, um, kinda messy.  Look at what a helper could do:

/*
 * Private memory #VE's are bad because the kernel has no way of
 * recovering from them and can only die. Newer TDX modules can
 * configured to inflict fewer #VE's on guests.  Do it when available.
 */
static inline int try_disable_sept_ve(td_addr)
{
	/* Does the TDX module support the #VE reduction feature? */
	if (!(features & TDX_FEATURES0_PENDING_EPT_VIOLATION_V2))
		return -ENOTSUP;

	/* Is this TD allowed to use the feature? */
	if (!(tdg_vm_rd(TDCS_CONFIG_FLAGS) &
	     TDCS_CONFIG_FLEXIBLE_PENDING_VE)))
		return -ENOTSUP;

	/* Keep #VE's enabled for splats in debugging environments: */
	if (td_attr & ATTR_DEBUG)
		return -ENOTSUP;

	if (!tdcs_ctls_set(TD_CTLS_PENDING_VE_DISABLE))
		return -ENOTSUP;

	return 0;
}

Then the code becomes:
	
	if (!try_disable_sept_ve(td_addr))
		sept_ve_disabled = true;
	else
		sept_ve_disabled = td_attr & ATTR_SEPT_VE_DISABLE;

See how it sets the state in *ONE* easy-to-understand place?

Oh, 'sept_ve_disabled' either gets disabled dynamically if it can, or it
gets read from the static state if not.

Oh, and if you ever have a comment that long with a bunch of
explanations of individual if() conditions, *PLEASE* try to break it up
in some way.  Otherwise readers just spent all their time trying to
match up the comment to the code.  It's not a fun game.

> +	    !(td_attr & ATTR_DEBUG)) {
> +		if (tdcs_ctls_set(TD_CTLS_PENDING_VE_DISABLE))
> +			sept_ve_disabled = true;
> +	}
> +
> +	if (!sept_ve_disabled) {
> +		const char *msg = "TD misconfiguration: SEPT #VE has to be disabled";
> +
> +		/* Relax SEPT #VE disable check for debug TD. */
>  		if (td_attr & ATTR_DEBUG)
>  			pr_warn("%s\n", msg);
>  		else
> diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
> index fdfd41511b02..29a61c72e4dd 100644
> --- a/arch/x86/include/asm/shared/tdx.h
> +++ b/arch/x86/include/asm/shared/tdx.h
> @@ -16,11 +16,27 @@
>  #define TDG_VP_VEINFO_GET		3
>  #define TDG_MR_REPORT			4
>  #define TDG_MEM_PAGE_ACCEPT		6
> +#define TDG_VM_RD			7
>  #define TDG_VM_WR			8
> +#define TDG_SYS_RD			11
>  
> -/* TDCS fields. To be used by TDG.VM.WR and TDG.VM.RD module calls */
> +/* TDX Global Metadata. To be used by TDG.SYS.RD */
> +#define TDCS_TDX_FEATURES0		0x0A00000300000008
> +
> +/* TDX TD-Scope Metadata. To be used by TDG.VM.WR and TDG.VM.RD */
> +#define TDCS_CONFIG_FLAGS		0x1110000300000016
> +#define TDCS_TD_CTLS			0x1110000300000017
>  #define TDCS_NOTIFY_ENABLES		0x9100000000000010
>  
> +/* TDCS_TDX_FEATURES0 bits */
> +#define TDX_FEATURES0_PENDING_EPT_VIOLATION_V2	BIT_ULL(16)
> +
> +/* 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)
> +
>  /* TDX hypercall Leaf IDs */
>  #define TDVMCALL_MAP_GPA		0x10001
>  #define TDVMCALL_GET_QUOTE		0x10002

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

[Kirill A. Shutemov]

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

[Huang, Kai]

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

[kirill.shutemov]

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

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

[Dave Hansen]

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

[Kirill A. Shutemov]

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 0/4] x86/tdx: Adjust TD settings on boot

[Kirill A. Shutemov]

On Mon, Mar 25, 2024 at 12:46:03PM +0200, Kirill A. Shutemov wrote:
> Adjust TD setting on boot:
> 
>   - Disable EPT violation #VE on private memory if TD can
>     control it;
> 
>   - Enable virtualization of topology-related CPUID leafs
>     X2APIC_APICID MSR;

Any feedback?

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

Re: [PATCHv2 0/4] x86/tdx: Adjust TD settings on boot

[Edgecombe, Rick P]

On Wed, 2024-04-10 at 17:37 +0300, Kirill A. Shutemov wrote:
> On Mon, Mar 25, 2024 at 12:46:03PM +0200, Kirill A. Shutemov wrote:
> > Adjust TD setting on boot:
> > 
> >    - Disable EPT violation #VE on private memory if TD can
> >      control it;
> > 
> >    - Enable virtualization of topology-related CPUID leafs
> >      X2APIC_APICID MSR;
> 
> Any feedback?

It is missing a lot of the normal things that come in coverletters like what is
the problem and importance. It might help attract more review.

Re: [PATCHv2 0/4] x86/tdx: Adjust TD settings on boot

[kirill.shutemov]

On Wed, Apr 10, 2024 at 02:41:13PM +0000, Edgecombe, Rick P wrote:
> On Wed, 2024-04-10 at 17:37 +0300, Kirill A. Shutemov wrote:
> > On Mon, Mar 25, 2024 at 12:46:03PM +0200, Kirill A. Shutemov wrote:
> > > Adjust TD setting on boot:
> > > 
> > >    - Disable EPT violation #VE on private memory if TD can
> > >      control it;
> > > 
> > >    - Enable virtualization of topology-related CPUID leafs
> > >      X2APIC_APICID MSR;
> > 
> > Any feedback?
> 
> It is missing a lot of the normal things that come in coverletters like what is
> the problem and importance. It might help attract more review.

What about this:

The patchset adjusts a few TD settings on boot for the optimal functioning
of the system:

  - Disable EPT violation #VE on private memory if TD can control it

    The newer TDX module allows the guest to control whether it wants to
    see #VE on EPT violation on private memory. The Linux kernel does not
    want such #VEs and needs to disable them.

  - Enable virtualization of topology-related CPUID leafs X2APIC_APICID MSR;

    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.

    It allows TDX guest to run with non-trivial topology configuration.
-- 
  Kiryl Shutsemau / Kirill A. Shutemov