x86/irq: Set up per host CPU posted interrupt descriptors

To support posted MSIs, create a posted interrupt descriptor (PID) for each
host CPU. Later on, when setting up interrupt affinity, the IOMMU's
interrupt remapping table entry (IRTE) will point to the physical address
of the matching CPU's PID.

Each PID is initialized with the owner CPU's physical APICID as the
destination.
Originally-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240423174114.526704-7-jacob.jun.pan@linux.intel.com

arch/x86/include/asm/hardirq.h

@@ -48,6 +48,9 @@ typedef struct {
 
 DECLARE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
 
+#ifdef CONFIG_X86_POSTED_MSI
+DECLARE_PER_CPU_ALIGNED(struct pi_desc, posted_msi_pi_desc);
+#endif
 #define __ARCH_IRQ_STAT
 
 #define inc_irq_stat(member)	this_cpu_inc(irq_stat.member)

arch/x86/include/asm/posted_intr.h

@@ -91,4 +91,10 @@ static inline void __pi_clear_sn(struct pi_desc *pi_desc)
 	pi_desc->notifications &= ~BIT(POSTED_INTR_SN);
 }
 
+#ifdef CONFIG_X86_POSTED_MSI
+extern void intel_posted_msi_init(void);
+#else
+static inline void intel_posted_msi_init(void) {};
+#endif /* X86_POSTED_MSI */
+
 #endif /* _X86_POSTED_INTR_H */

arch/x86/kernel/cpu/common.c

@@ -68,6 +68,7 @@
 #include <asm/traps.h>
 #include <asm/sev.h>
 #include <asm/tdx.h>
+#include <asm/posted_intr.h>
 
 #include "cpu.h"
 
@@ -2227,6 +2228,8 @@ void cpu_init(void)
 		barrier();
 
 		x2apic_setup();
+
+		intel_posted_msi_init();
 	}
 
 	mmgrab(&init_mm);

arch/x86/kernel/irq.c

@@ -22,6 +22,8 @@
 #include <asm/desc.h>
 #include <asm/traps.h>
 #include <asm/thermal.h>
+#include <asm/posted_intr.h>
+#include <asm/irq_remapping.h>
 
 #define CREATE_TRACE_POINTS
 #include <asm/trace/irq_vectors.h>
@@ -334,6 +336,27 @@ DEFINE_IDTENTRY_SYSVEC_SIMPLE(sysvec_kvm_posted_intr_nested_ipi)
 }
 #endif
 
+#ifdef CONFIG_X86_POSTED_MSI
+
+/* Posted Interrupt Descriptors for coalesced MSIs to be posted */
+DEFINE_PER_CPU_ALIGNED(struct pi_desc, posted_msi_pi_desc);
+
+void intel_posted_msi_init(void)
+{
+	u32 destination;
+	u32 apic_id;
+
+	this_cpu_write(posted_msi_pi_desc.nv, POSTED_MSI_NOTIFICATION_VECTOR);
+
+	/*
+	 * APIC destination ID is stored in bit 8:15 while in XAPIC mode.
+	 * VT-d spec. CH 9.11
+	 */
+	apic_id = this_cpu_read(x86_cpu_to_apicid);
+	destination = x2apic_enabled() ? apic_id : apic_id << 8;
+	this_cpu_write(posted_msi_pi_desc.ndst, destination);
+}
+#endif /* X86_POSTED_MSI */
 
 #ifdef CONFIG_HOTPLUG_CPU
 /* A cpu has been removed from cpu_online_mask.  Reset irq affinities. */