[PATCH v3 4/6] x86/tdx: Add TDX Guest event notify interrupt vector support

[Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>]

Allocate 0xec IRQ vector address for TDX guest to receive the event
completion notification from VMM. Since this vector address will be
sent to VMM via hypercall, allocate a fixed address and move
LOCAL_TIMER_VECTOR vector address by 1 byte. Also add related IDT
handler to process the notification event.

It will be mainly used by attestation driver to receive Quote event
completion notification from host.

Add support to track the notification event status via /proc/interrupts.

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     |  1 +
 arch/x86/include/asm/idtentry.h    |  4 +++
 arch/x86/include/asm/irq_vectors.h |  7 ++++-
 arch/x86/include/asm/tdx.h         |  2 ++
 arch/x86/kernel/irq.c              |  7 +++++
 arch/x86/kernel/tdx.c              | 41 ++++++++++++++++++++++++++++++
 6 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h
index 07d79fa9c5c6..40d0534e7d82 100644
--- a/arch/x86/include/asm/hardirq.h
+++ b/arch/x86/include/asm/hardirq.h
@@ -46,6 +46,7 @@ typedef struct {
 #endif
 #if IS_ENABLED(CONFIG_INTEL_TDX_GUEST)
 	unsigned int tdg_ve_count;
+	unsigned int irq_tdg_event_notify_count;
 #endif
 } ____cacheline_aligned irq_cpustat_t;
 
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index 8ccc81d653b3..6f3472a88e9c 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -693,6 +693,10 @@ DECLARE_IDTENTRY_SYSVEC(HYPERVISOR_CALLBACK_VECTOR,	sysvec_xen_hvm_callback);
 DECLARE_IDTENTRY_SYSVEC(HYPERVISOR_CALLBACK_VECTOR,	sysvec_kvm_asyncpf_interrupt);
 #endif
 
+#ifdef CONFIG_INTEL_TDX_GUEST
+DECLARE_IDTENTRY_SYSVEC(TDX_GUEST_EVENT_NOTIFY_VECTOR,	sysvec_tdg_event_notify);
+#endif
+
 #undef X86_TRAP_OTHER
 
 #endif
diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index 43dcb9284208..82ac0c0a34b1 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -104,7 +104,12 @@
 #define HYPERV_STIMER0_VECTOR		0xed
 #endif
 
-#define LOCAL_TIMER_VECTOR		0xec
+#if IS_ENABLED(CONFIG_INTEL_TDX_GUEST)
+/* Vector on which TDX Guest event notification is delivered */
+#define TDX_GUEST_EVENT_NOTIFY_VECTOR	0xec
+#endif
+
+#define LOCAL_TIMER_VECTOR		0xeb
 
 #define NR_VECTORS			 256
 
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 1599aa4850e5..a7ebc6e448d7 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -100,6 +100,8 @@ int tdx_mcall_tdreport(u64 data, u64 reportdata);
 
 int tdx_hcall_get_quote(u64 data);
 
+extern void (*tdg_event_notify_handler)(void);
+
 /*
  * To support I/O port access in decompressor or early kernel init
  * code, since #VE exception handler cannot be used, use paravirt
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 669869bd46ec..a4fe53c8c18f 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -182,11 +182,18 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 			   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");
+
+	seq_printf(p, "%*s: ", prec, "TGN");
+	for_each_online_cpu(j)
+		seq_printf(p, "%10u ",
+			   irq_stats(j)->irq_tdg_event_notify_count);
+	seq_puts(p, "  TDX Guest event notification\n");
 #endif
 	return 0;
 }
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index 27e56ab0d4a2..334cac8792c2 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -11,6 +11,11 @@
 #include <asm/tdx.h>
 #include <asm/cmdline.h>
 #include <asm/i8259.h>
+#include <asm/apic.h>
+#include <asm/idtentry.h>
+#include <asm/irq_regs.h>
+#include <asm/desc.h>
+#include <asm/idtentry.h>
 #include <asm/vmx.h>
 #include <asm/insn.h>
 #include <asm/insn-eval.h>
@@ -54,6 +59,14 @@ static struct {
 	unsigned long attributes;
 } td_info __ro_after_init;
 
+/*
+ * Currently it will be used only by the attestation
+ * driver. So, race condition with read/write operation
+ * is not considered.
+ */
+void (*tdg_event_notify_handler)(void);
+EXPORT_SYMBOL_GPL(tdg_event_notify_handler);
+
 /*
  * Wrapper for standard use of __tdx_hypercall with BUG_ON() check
  * for TDCALL error.
@@ -152,6 +165,28 @@ static bool tdg_perfmon_enabled(void)
 	return td_info.attributes & BIT(63);
 }
 
+/* TDX guest event notification handler */
+DEFINE_IDTENTRY_SYSVEC(sysvec_tdg_event_notify)
+{
+	struct pt_regs *old_regs = set_irq_regs(regs);
+
+	inc_irq_stat(irq_tdg_event_notify_count);
+
+	if (tdg_event_notify_handler)
+		tdg_event_notify_handler();
+
+	/*
+	 * The hypervisor requires that the APIC EOI should be acked.
+	 * If the APIC EOI is not acked, the APIC ISR bit for the
+	 * TDX_GUEST_EVENT_NOTIFY_VECTOR will not be cleared and then it
+	 * will block the interrupt whose vector is lower than
+	 * TDX_GUEST_EVENT_NOTIFY_VECTOR.
+	 */
+	ack_APIC_irq();
+
+	set_irq_regs(old_regs);
+}
+
 /*
  * tdx_mcall_tdreport() - Generate TDREPORT_STRUCT using TDCALL.
  *
@@ -720,5 +755,11 @@ void __init tdx_early_init(void)
 		lock_kernel_down("TDX guest init", lockdown_reason);
 	}
 
+	alloc_intr_gate(TDX_GUEST_EVENT_NOTIFY_VECTOR,
+			asm_sysvec_tdg_event_notify);
+
+	if (tdx_hcall_set_notify_intr(TDX_GUEST_EVENT_NOTIFY_VECTOR))
+		pr_warn("Setting event notification interrupt failed\n");
+
 	pr_info("Guest initialized\n");
 }
-- 
2.25.1