[PATCH v1 0/4] Add TDX Guest Support (Debug support)

[PATCH v1 0/4] Add TDX Guest Support (Debug support)

[Kuppuswamy Sathyanarayanan]

Hi All,

Intel's Trust Domain Extensions (TDX) protect guest VMs from malicious
hosts and some physical attacks.

Following patches adds tracepoint support for TDX Guest TDCALL requests
and #VE exceptions. It also includes helper function to detect TD-DEBUG
mode which will be used by patches in other TDX series to add TD-DEBUG
mode specific features support.

This series is the continuation of the following TDX guest related patches.

[set 1] - https://lore.kernel.org/patchwork/project/lkml/list/?series=505232
[set 2] - https://lore.kernel.org/patchwork/project/lkml/list/?series=506230
[set 3] - https://lore.kernel.org/patchwork/project/lkml/list/?series=506231
[set 4] - https://lore.kernel.org/patchwork/project/lkml/list/?series=506232

Also please note that this series alone is not necessarily fully
functional. You need to apply all the above 4 patch series to get 
a fully functional TDX guest.



Kuppuswamy Sathyanarayanan (3):
  x86/tdx: Add TDCALL tracepoint
  x86/tdx: Expose TDX Guest #VE count in /proc/interrupts
  x86/tdx: Add tdg_debug_enabled() interface

Sean Christopherson (1):
  x86/tdx: Add #VE tracepoint

 arch/x86/include/asm/hardirq.h   |   3 +
 arch/x86/include/asm/tdx.h       |   1 +
 arch/x86/include/asm/trace/tdx.h | 150 +++++++++++++++++++++++++++++++
 arch/x86/kernel/irq.c            |   6 ++
 arch/x86/kernel/tdx.c            |  71 ++++++++++++---
 arch/x86/kernel/traps.c          |   2 +
 6 files changed, 220 insertions(+), 13 deletions(-)
 create mode 100644 arch/x86/include/asm/trace/tdx.h

-- 
2.25.1

[PATCH v1 1/4] x86/tdx: Add #VE tracepoint

[Kuppuswamy Sathyanarayanan]

From: Sean Christopherson <sean.j.christopherson@intel.com>

Add tracepoint for tracing TDX guest #VE exceptions. It will dump
RIP, exit reason, exit qual, GPA, instruction length and instruction
info for each #VE exception occurred.

Also, make trace points RCU idle safe to avoid warnings when RCU
debugging is enabled.

Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---
 arch/x86/include/asm/trace/tdx.h | 51 ++++++++++++++++++++++++++++++++
 arch/x86/kernel/tdx.c            |  6 ++++
 2 files changed, 57 insertions(+)
 create mode 100644 arch/x86/include/asm/trace/tdx.h

diff --git a/arch/x86/include/asm/trace/tdx.h b/arch/x86/include/asm/trace/tdx.h
new file mode 100644
index 000000000000..e045e276009e
--- /dev/null
+++ b/arch/x86/include/asm/trace/tdx.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#if !defined(_TRACE_TDX_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_TDX_H
+
+#include <linux/tracepoint.h>
+
+#include <uapi/asm/vmx.h>
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM tdx
+
+#ifdef CONFIG_INTEL_TDX_GUEST
+
+TRACE_EVENT(tdg_virtualization_exception,
+	    TP_PROTO(u64 rip, u32 exit_reason, u64 exit_qual,
+		     u64 gpa, u32 instr_len, u32 instr_info),
+	    TP_ARGS(rip, exit_reason, exit_qual, gpa, instr_len,
+		    instr_info),
+	    TP_STRUCT__entry(
+			     __field(u64, rip)
+			     __field(u64, exit_qual)
+			     __field(u64, gpa)
+			     __field(u32, exit_reason)
+			     __field(u32, instr_len)
+			     __field(u32, instr_info)
+			     ),
+	    TP_fast_assign(
+			   __entry->rip = rip;
+			   __entry->exit_qual = exit_qual;
+			   __entry->gpa = gpa;
+			   __entry->exit_reason = exit_reason;
+			   __entry->instr_len = instr_len;
+			   __entry->instr_info = instr_info;
+			   ),
+	    TP_printk("reason %s rip 0x%016llx len %u info 0x%08x qual 0x%016llx gpa 0x%016llx",
+		      __print_symbolic(__entry->exit_reason, VMX_EXIT_REASONS),
+		      __entry->rip, __entry->instr_len, __entry->instr_info,
+		      __entry->exit_qual, __entry->gpa
+		      )
+	    );
+
+#endif // CONFIG_INTEL_TDX_GUEST
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH asm/trace/
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE tdx
+#endif /* _TRACE_TDX_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index 4639206d99f3..67687cf3e631 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -16,6 +16,9 @@
 #include <linux/sched/signal.h> /* force_sig_fault() */
 #include <linux/swiotlb.h>
 
+#define CREATE_TRACE_POINTS
+#include <asm/trace/tdx.h>
+
 /* TDX Module call Leaf IDs */
 #define TDINFO				1
 #define TDGETVEINFO			3
@@ -407,6 +410,9 @@ int tdg_handle_virtualization_exception(struct pt_regs *regs,
 	unsigned long val;
 	int ret = 0;
 
+	trace_tdg_virtualization_exception_rcuidle(regs->ip, ve->exit_reason,
+		ve->exit_qual, ve->gpa, ve->instr_len, ve->instr_info);
+
 	switch (ve->exit_reason) {
 	case EXIT_REASON_HLT:
 		tdg_halt();
-- 
2.25.1

[PATCH v1 2/4] x86/tdx: Add TDCALL tracepoint

[Kuppuswamy Sathyanarayanan]

Add TDCALL tracepoint in __tdx_module_call() and
__tdx_hypercall() helper functions. These two helper functions
are core calls for triggering the "TDCALL" instruction. Having
a trace point for each TDCALL is useful for debugging and
performance analysis, as well as testing.

For __tdx_module_call(), it will dump info about TDCALL leaf
ID (RAX) and input parameters (RCX, RDX, R8, R9) in entry path
and TDCALL return status (RAX) and output parameters (RCX, RDX,
R8, R9, R10, R11) in exit path.

For __tdx_hypercall(), it will dump info about TDG.VP.VMCALL sub
ID (R11), and input parameters (R12-R15) in entry path and
TDG.VP.VMCALL return status (R10) and output parameters (R11-R15)
in exit path.

Also, make trace points RCU idle safe to avoid warnings when RCU
debugging is enabled.

Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---
 arch/x86/include/asm/trace/tdx.h | 99 ++++++++++++++++++++++++++++++++
 arch/x86/kernel/tdx.c            | 60 ++++++++++++++-----
 2 files changed, 146 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/trace/tdx.h b/arch/x86/include/asm/trace/tdx.h
index e045e276009e..a94ac1e73b6c 100644
--- a/arch/x86/include/asm/trace/tdx.h
+++ b/arch/x86/include/asm/trace/tdx.h
@@ -39,6 +39,105 @@ TRACE_EVENT(tdg_virtualization_exception,
 		      )
 	    );
 
+TRACE_EVENT(tdx_module_call_enter,
+	    TP_PROTO(u64 id, u64 rcx, u64 rdx, u64 r8, u64 r9),
+	    TP_ARGS(id, rcx, rdx, r8, r9),
+	    TP_STRUCT__entry(
+		__field(u64, id)
+		__field(u64, rcx)
+		__field(u64, rdx)
+		__field(u64, r8)
+		__field(u64, r9)
+		),
+	    TP_fast_assign(
+		__entry->id  = id;
+		__entry->rcx = rcx;
+		__entry->rdx = rdx;
+		__entry->r8  = r8;
+		__entry->r9  = r9;
+		),
+	    TP_printk("id %lld rcx 0x%016llx rdx 0x%016llx r8 0x%016llx r9 0x%016llx",
+		      __entry->id, __entry->rcx, __entry->rdx,
+		      __entry->r8, __entry->r9
+		      )
+	    );
+
+TRACE_EVENT(tdx_module_call_exit,
+	    TP_PROTO(u64 rax, u64 rcx, u64 rdx, u64 r8, u64 r9,
+		     u64 r10, u64 r11),
+	    TP_ARGS(rax, rcx, rdx, r8, r9, r10, r11),
+	    TP_STRUCT__entry(
+		__field(u64, rax)
+		__field(u64, rcx)
+		__field(u64, rdx)
+		__field(u64, r8)
+		__field(u64, r9)
+		__field(u64, r10)
+		__field(u64, r11)
+		),
+	    TP_fast_assign(
+		__entry->rax = rax;
+		__entry->rcx = rcx;
+		__entry->rdx = rdx;
+		__entry->r8  = r8;
+		__entry->r9  = r9;
+		__entry->r10 = r10;
+		__entry->r11 = r11;
+		),
+	    TP_printk("ret %lld rcx 0x%016llx rdx 0x%016llx r8 0x%016llx r9 0x%016llx r10 0x%016llx r11 0x%016llx",
+		      __entry->rax, __entry->rcx, __entry->rdx,
+		      __entry->r8, __entry->r9, __entry->r10, __entry->r11
+		      )
+	    );
+
+TRACE_EVENT(tdx_hypercall_enter,
+	    TP_PROTO(u64 id, u64 r12, u64 r13, u64 r14, u64 r15),
+	    TP_ARGS(id, r12, r13, r14, r15),
+	    TP_STRUCT__entry(
+		__field(u64, id)
+		__field(u64, r12)
+		__field(u64, r13)
+		__field(u64, r14)
+		__field(u64, r15)
+		),
+	    TP_fast_assign(
+		__entry->id  = id;
+		__entry->r12 = r12;
+		__entry->r13 = r13;
+		__entry->r14 = r14;
+		__entry->r15 = r15;
+		),
+	    TP_printk("subfn %lld r12 0x%016llx r13 0x%016llx r14 0x%016llx r15 0x%016llx",
+		      __entry->id, __entry->r12, __entry->r13,
+		      __entry->r14, __entry->r15
+		      )
+	    );
+
+TRACE_EVENT(tdx_hypercall_exit,
+	    TP_PROTO(u64 r10, u64 r11, u64 r12, u64 r13, u64 r14, u64 r15),
+	    TP_ARGS(r10, r11, r12, r13, r14, r15),
+	    TP_STRUCT__entry(
+		__field(u64, r10)
+		__field(u64, r11)
+		__field(u64, r12)
+		__field(u64, r13)
+		__field(u64, r14)
+		__field(u64, r15)
+		),
+	    TP_fast_assign(
+		__entry->r10 = r10;
+		__entry->r11 = r11;
+		__entry->r12 = r12;
+		__entry->r13 = r13;
+		__entry->r14 = r14;
+		__entry->r15 = r15;
+		),
+	    TP_printk("ret %lld r11 0x%016llx r12 0x%016llx r13 0x%016llx r14 0x%016llx r15 0x%016llx",
+		      __entry->r10, __entry->r11, __entry->r12,
+		      __entry->r13, __entry->r14, __entry->r15
+		      )
+	    );
+
 #endif // CONFIG_INTEL_TDX_GUEST
 
 #undef TRACE_INCLUDE_PATH
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index 67687cf3e631..99e6701e7f48 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -63,6 +63,33 @@ static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14,
 	return out->r10;
 }
 
+/* Traced version of _tdx_hypercall() */
+static u64 _trace_tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14, u64 r15,
+				struct tdx_hypercall_output *out)
+{
+	u64 err;
+
+	trace_tdx_hypercall_enter_rcuidle(fn, r12, r13, r14, r15);
+	err = _tdx_hypercall(fn, r12, r13, r14, r15, out);
+	trace_tdx_hypercall_exit_rcuidle(err, out->r11, out->r12, out->r13,
+					 out->r14, out->r15);
+
+	return err;
+}
+
+static u64 __trace_tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
+				   struct tdx_module_output *out)
+{
+	u64 err;
+
+	trace_tdx_module_call_enter_rcuidle(fn, rcx, rdx, r8, r9);
+	err = __tdx_module_call(fn, rcx, rdx, r8, r9, out);
+	trace_tdx_module_call_exit_rcuidle(err, out->rcx, out->rdx, out->r8,
+					   out->r9, out->r10, out->r11);
+
+	return err;
+}
+
 static inline bool cpuid_has_tdx_guest(void)
 {
 	u32 eax, sig[3];
@@ -101,7 +128,7 @@ static void tdg_get_info(void)
 	u64 ret;
 	struct tdx_module_output out = {0};
 
-	ret = __tdx_module_call(TDINFO, 0, 0, 0, 0, &out);
+	ret = __trace_tdx_module_call(TDINFO, 0, 0, 0, 0, &out);
 
 	BUG_ON(ret);
 
@@ -116,7 +143,7 @@ static void tdg_accept_page(phys_addr_t gpa)
 {
 	u64 ret;
 
-	ret = __tdx_module_call(TDACCEPTPAGE, gpa, 0, 0, 0, NULL);
+	ret = __trace_tdx_module_call(TDACCEPTPAGE, gpa, 0, 0, 0, NULL);
 
 	BUG_ON(ret && ret != TDX_PAGE_ALREADY_ACCEPTED);
 }
@@ -157,7 +184,8 @@ static __cpuidle void tdg_halt(void)
 {
 	u64 ret;
 
-	ret = _tdx_hypercall(EXIT_REASON_HLT, irqs_disabled(), 0, 0, 0, NULL);
+	ret = _trace_tdx_hypercall(EXIT_REASON_HLT, irqs_disabled(),
+				   0, 0, 0, NULL);
 
 	/* It should never fail */
 	BUG_ON(ret);
@@ -174,7 +202,7 @@ static __cpuidle void tdg_safe_halt(void)
 	local_irq_enable();
 
 	/* IRQ is enabled, So set R12 as 0 */
-	ret = _tdx_hypercall(EXIT_REASON_HLT, 0, 0, 0, 0, NULL);
+	ret = _trace_tdx_hypercall(EXIT_REASON_HLT, 0, 0, 0, 0, NULL);
 
 	/* It should never fail */
 	BUG_ON(ret);
@@ -209,7 +237,7 @@ static u64 tdg_read_msr_safe(unsigned int msr, int *err)
 
 	WARN_ON_ONCE(tdg_is_context_switched_msr(msr));
 
-	ret = _tdx_hypercall(EXIT_REASON_MSR_READ, msr, 0, 0, 0, &out);
+	ret = _trace_tdx_hypercall(EXIT_REASON_MSR_READ, msr, 0, 0, 0, &out);
 
 	*err = ret ? -EIO : 0;
 
@@ -223,8 +251,8 @@ static int tdg_write_msr_safe(unsigned int msr, unsigned int low,
 
 	WARN_ON_ONCE(tdg_is_context_switched_msr(msr));
 
-	ret = _tdx_hypercall(EXIT_REASON_MSR_WRITE, msr, (u64)high << 32 | low,
-			     0, 0, NULL);
+	ret = _trace_tdx_hypercall(EXIT_REASON_MSR_WRITE, msr,
+				   (u64)high << 32 | low, 0, 0, NULL);
 
 	return ret ? -EIO : 0;
 }
@@ -234,7 +262,8 @@ static void tdg_handle_cpuid(struct pt_regs *regs)
 	u64 ret;
 	struct tdx_hypercall_output out = {0};
 
-	ret = _tdx_hypercall(EXIT_REASON_CPUID, regs->ax, regs->cx, 0, 0, &out);
+	ret = _trace_tdx_hypercall(EXIT_REASON_CPUID, regs->ax,
+				   regs->cx, 0, 0, &out);
 
 	WARN_ON(ret);
 
@@ -264,11 +293,16 @@ static void tdg_handle_io(struct pt_regs *regs, u32 exit_qual)
 	/* I/O strings ops are unrolled at build time. */
 	BUG_ON(string);
 
-	ret = _tdx_hypercall(EXIT_REASON_IO_INSTRUCTION, size, out, port,
-			     regs->ax, &outh);
 	if (!out) {
+		ret = _trace_tdx_hypercall(EXIT_REASON_IO_INSTRUCTION,
+					   size, out, port, regs->ax,
+					   &outh);
 		regs->ax &= ~mask;
 		regs->ax |= (ret ? UINT_MAX : outh.r11) & mask;
+	} else {
+		ret = _tdx_hypercall(EXIT_REASON_IO_INSTRUCTION,
+				     size, out, port, regs->ax,
+				     &outh);
 	}
 }
 
@@ -278,8 +312,8 @@ static unsigned long tdg_mmio(int size, bool write, unsigned long addr,
 	struct tdx_hypercall_output out = {0};
 	u64 err;
 
-	err = _tdx_hypercall(EXIT_REASON_EPT_VIOLATION, size, write,
-			     addr, *val, &out);
+	err = _trace_tdx_hypercall(EXIT_REASON_EPT_VIOLATION, size, write,
+				   addr, *val, &out);
 	*val = out.r11;
 	return err;
 }
@@ -392,7 +426,7 @@ unsigned long tdg_get_ve_info(struct ve_info *ve)
 	 * additional #VEs are permitted (but we don't expect them to
 	 * happen unless you panic).
 	 */
-	ret = __tdx_module_call(TDGETVEINFO, 0, 0, 0, 0, &out);
+	ret = __trace_tdx_module_call(TDGETVEINFO, 0, 0, 0, 0, &out);
 
 	ve->exit_reason = out.rcx;
 	ve->exit_qual   = out.rdx;
-- 
2.25.1

[PATCH v1 3/4] x86/tdx: Expose TDX Guest #VE count in /proc/interrupts

[Kuppuswamy Sathyanarayanan]

Add support to expose TD Guest Virtualization Exception (#VE) count
in /proc/interrupts. It is useful in performance analysis of TD Guest.

Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---
 arch/x86/include/asm/hardirq.h | 3 +++
 arch/x86/kernel/irq.c          | 6 ++++++
 arch/x86/kernel/traps.c        | 2 ++
 3 files changed, 11 insertions(+)

diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h
index 275e7fd20310..07d79fa9c5c6 100644
--- a/arch/x86/include/asm/hardirq.h
+++ b/arch/x86/include/asm/hardirq.h
@@ -44,6 +44,9 @@ typedef struct {
 	unsigned int irq_hv_reenlightenment_count;
 	unsigned int hyperv_stimer0_count;
 #endif
+#if IS_ENABLED(CONFIG_INTEL_TDX_GUEST)
+	unsigned int tdg_ve_count;
+#endif
 } ____cacheline_aligned irq_cpustat_t;
 
 DECLARE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index e28f6a5d14f1..669869bd46ec 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -181,6 +181,12 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 		seq_printf(p, "%10u ",
 			   irq_stats(j)->kvm_posted_intr_wakeup_ipis);
 	seq_puts(p, "  Posted-interrupt wakeup event\n");
+#endif
+#if IS_ENABLED(CONFIG_INTEL_TDX_GUEST)
+	seq_printf(p, "%*s: ", prec, "TGV");
+	for_each_online_cpu(j)
+		seq_printf(p, "%10u ", irq_stats(j)->tdg_ve_count);
+	seq_puts(p, "  TDX Guest VE event\n");
 #endif
 	return 0;
 }
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index d860fdee9cfe..3a6cfde8ca85 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -1186,6 +1186,8 @@ DEFINE_IDTENTRY(exc_virtualization_exception)
 
 	RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
 
+	inc_irq_stat(tdg_ve_count);
+
 	/*
 	 * NMIs/Machine-checks/Interrupts will be in a disabled state
 	 * till TDGETVEINFO TDCALL is executed. This prevents #VE
-- 
2.25.1

[PATCH v1 4/4] x86/tdx: Add tdg_debug_enabled() interface

[Kuppuswamy Sathyanarayanan]

A guest TD is defined as debuggable if its ATTRIBUTES.DEBUG bit is 1.
In this mode, the host VMM can use Intel TDX functions to access
secret TD state that is not accessible for non-debuggable TDs. A
debuggable TD is, by nature, untrusted.

Since the TD’s ATTRIBUTES are included in the TDG.MR.REPORT, the TD’s
debuggability state can be known to any third party to which the TD
attests. TD Attributes are initialized during TD INIT call. You can get
more details about debug features in Intel Trust Domain Extensions
(Intel TDX) Module Architecture specification, sec 13.3.

Add a new interface to detect the TDX debug mode. This will be used by
follow-on patches. Examples of its usage are, when adding command line
debug options to disable TDX features like driver or port filter,
tdg_debug_enabled() is used to make sure it is used only in debug
mode.

https://software.intel.com/content/dam/develop/external/us/en/documents/tdx-module-1eas-v0.85.039.pdf

Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---
 arch/x86/include/asm/tdx.h | 1 +
 arch/x86/kernel/tdx.c      | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 665c8cf57d5b..1c0d4bf693a3 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -67,6 +67,7 @@ enum tdx_map_type {
 
 #ifdef CONFIG_INTEL_TDX_GUEST
 
+bool tdg_debug_enabled(void);
 void __init tdx_early_init(void);
 
 bool tdx_prot_guest_has(unsigned long flag);
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index 99e6701e7f48..1226c1b234bd 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -123,6 +123,11 @@ phys_addr_t tdg_shared_mask(void)
 	return 1ULL << (td_info.gpa_width - 1);
 }
 
+bool tdg_debug_enabled(void)
+{
+	return td_info.attributes & BIT(0);
+}
+
 static void tdg_get_info(void)
 {
 	u64 ret;
-- 
2.25.1