[PATCH RFC 13/13] iommu/vt-d: Enable posted mode for device MSIs

[Jacob Pan]

With posted MSI feature is enabled on the CPU side, iommu IRTEs for
device MSIs can be allocated, activated, and programed in posted mode.
This means that IRTEs are linked with their respective PIDs of the
target CPU.

Excluding the following:
- legacy devices IOAPIC, HPET (may be needed for booting, not a source
of high MSIs)
- VT-d's own IRQs (not remappable).

Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/posted_intr.h  |  1 +
 drivers/iommu/intel/irq_remapping.c | 55 ++++++++++++++++++++++++++---
 2 files changed, 52 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/posted_intr.h b/arch/x86/include/asm/posted_intr.h
index 12a4fa3ff60e..c6d245f53225 100644
--- a/arch/x86/include/asm/posted_intr.h
+++ b/arch/x86/include/asm/posted_intr.h
@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _X86_POSTED_INTR_H
 #define _X86_POSTED_INTR_H
+#include <asm/irq_vectors.h>
 
 #define POSTED_INTR_ON  0
 #define POSTED_INTR_SN  1
diff --git a/drivers/iommu/intel/irq_remapping.c b/drivers/iommu/intel/irq_remapping.c
index 971e6c37002f..1b88846d5338 100644
--- a/drivers/iommu/intel/irq_remapping.c
+++ b/drivers/iommu/intel/irq_remapping.c
@@ -19,6 +19,7 @@
 #include <asm/cpu.h>
 #include <asm/irq_remapping.h>
 #include <asm/pci-direct.h>
+#include <asm/posted_intr.h>
 
 #include "iommu.h"
 #include "../irq_remapping.h"
@@ -49,6 +50,7 @@ struct irq_2_iommu {
 	u16 sub_handle;
 	u8  irte_mask;
 	enum irq_mode mode;
+	bool posted_msi;
 };
 
 struct intel_ir_data {
@@ -1118,6 +1120,14 @@ static void prepare_irte(struct irte *irte, int vector, unsigned int dest)
 	irte->redir_hint = 1;
 }
 
+static void prepare_irte_posted(struct irte *irte)
+{
+	memset(irte, 0, sizeof(*irte));
+
+	irte->present = 1;
+	irte->p_pst = 1;
+}
+
 struct irq_remap_ops intel_irq_remap_ops = {
 	.prepare		= intel_prepare_irq_remapping,
 	.enable			= intel_enable_irq_remapping,
@@ -1125,6 +1135,7 @@ struct irq_remap_ops intel_irq_remap_ops = {
 	.reenable		= reenable_irq_remapping,
 	.enable_faulting	= enable_drhd_fault_handling,
 };
+
 #ifdef CONFIG_X86_POSTED_MSI
 
 static u64 get_pi_desc_addr(struct irq_data *irqd)
@@ -1133,6 +1144,29 @@ static u64 get_pi_desc_addr(struct irq_data *irqd)
 
 	return __pa(per_cpu_ptr(&posted_interrupt_desc, cpu));
 }
+
+static void intel_ir_reconfigure_irte_posted(struct irq_data *irqd)
+{
+	struct intel_ir_data *ir_data = irqd->chip_data;
+	struct irte *irte = &ir_data->irte_entry;
+	struct irte irte_pi;
+	u64 pid_addr;
+
+	pid_addr = get_pi_desc_addr(irqd);
+
+	memset(&irte_pi, 0, sizeof(irte_pi));
+
+	/* The shared IRTE already be set up as posted during alloc_irte */
+	dmar_copy_shared_irte(&irte_pi, irte);
+
+	irte_pi.pda_l = (pid_addr >> (32 - PDA_LOW_BIT)) & ~(-1UL << PDA_LOW_BIT);
+	irte_pi.pda_h = (pid_addr >> 32) & ~(-1UL << PDA_HIGH_BIT);
+
+	modify_irte(&ir_data->irq_2_iommu, &irte_pi);
+}
+
+#else
+static inline void intel_ir_reconfigure_irte_posted(struct irq_data *irqd) {}
 #endif
 
 static void intel_ir_reconfigure_irte(struct irq_data *irqd, bool force)
@@ -1148,8 +1182,9 @@ static void intel_ir_reconfigure_irte(struct irq_data *irqd, bool force)
 	irte->vector = cfg->vector;
 	irte->dest_id = IRTE_DEST(cfg->dest_apicid);
 
-	/* Update the hardware only if the interrupt is in remapped mode. */
-	if (force || ir_data->irq_2_iommu.mode == IRQ_REMAPPING)
+	if (ir_data->irq_2_iommu.posted_msi)
+		intel_ir_reconfigure_irte_posted(irqd);
+	else if (force || ir_data->irq_2_iommu.mode == IRQ_REMAPPING)
 		modify_irte(&ir_data->irq_2_iommu, irte);
 }
 
@@ -1203,7 +1238,7 @@ static int intel_ir_set_vcpu_affinity(struct irq_data *data, void *info)
 	struct intel_ir_data *ir_data = data->chip_data;
 	struct vcpu_data *vcpu_pi_info = info;
 
-	/* stop posting interrupts, back to remapping mode */
+	/* stop posting interrupts, back to the default mode */
 	if (!vcpu_pi_info) {
 		modify_irte(&ir_data->irq_2_iommu, &ir_data->irte_entry);
 	} else {
@@ -1300,10 +1335,14 @@ static void intel_irq_remapping_prepare_irte(struct intel_ir_data *data,
 {
 	struct irte *irte = &data->irte_entry;
 
-	prepare_irte(irte, irq_cfg->vector, irq_cfg->dest_apicid);
+	if (data->irq_2_iommu.mode == IRQ_POSTING)
+		prepare_irte_posted(irte);
+	else
+		prepare_irte(irte, irq_cfg->vector, irq_cfg->dest_apicid);
 
 	switch (info->type) {
 	case X86_IRQ_ALLOC_TYPE_IOAPIC:
+		prepare_irte(irte, irq_cfg->vector, irq_cfg->dest_apicid);
 		/* Set source-id of interrupt request */
 		set_ioapic_sid(irte, info->devid);
 		apic_printk(APIC_VERBOSE, KERN_DEBUG "IOAPIC[%d]: Set IRTE entry (P:%d FPD:%d Dst_Mode:%d Redir_hint:%d Trig_Mode:%d Dlvry_Mode:%X Avail:%X Vector:%02X Dest:%08X SID:%04X SQ:%X SVT:%X)\n",
@@ -1315,10 +1354,18 @@ static void intel_irq_remapping_prepare_irte(struct intel_ir_data *data,
 		sub_handle = info->ioapic.pin;
 		break;
 	case X86_IRQ_ALLOC_TYPE_HPET:
+		prepare_irte(irte, irq_cfg->vector, irq_cfg->dest_apicid);
 		set_hpet_sid(irte, info->devid);
 		break;
 	case X86_IRQ_ALLOC_TYPE_PCI_MSI:
 	case X86_IRQ_ALLOC_TYPE_PCI_MSIX:
+		if (posted_msi_supported()) {
+			prepare_irte_posted(irte);
+			data->irq_2_iommu.posted_msi = 1;
+		} else {
+			prepare_irte(irte, irq_cfg->vector, irq_cfg->dest_apicid);
+		}
+
 		set_msi_sid(irte,
 			    pci_real_dma_dev(msi_desc_to_pci_dev(info->desc)));
 		break;
-- 
2.25.1