iommu/x86: Replace IOMMU_CAP_INTR_REMAP with IRQ_DOMAIN_FLAG_ISOLATED_MSI

On x86 platforms when the HW can support interrupt remapping the iommu
driver creates an irq_domain for the IR hardware and creates a child MSI
irq_domain.

When the global irq_remapping_enabled is set, the IR MSI domain is
assigned to the PCI devices (by intel_irq_remap_add_device(), or
amd_iommu_set_pci_msi_domain()) making those devices have the isolated MSI
property.

Due to how interrupt domains work, setting IRQ_DOMAIN_FLAG_ISOLATED_MSI on
the parent IR domain will cause all struct devices attached to it to
return true from msi_device_has_isolated_msi(). This replaces the
IOMMU_CAP_INTR_REMAP flag as all places using IOMMU_CAP_INTR_REMAP also
call msi_device_has_isolated_msi()

Set the flag and delete the cap.

Link: https://lore.kernel.org/r/7-v3-3313bb5dd3a3+10f11-secure_msi_jgg@nvidia.comTested-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/iommu/amd/iommu.c

@@ -2271,8 +2271,6 @@ static bool amd_iommu_capable(struct device *dev, enum iommu_cap cap)
 	switch (cap) {
 	case IOMMU_CAP_CACHE_COHERENCY:
 		return true;
-	case IOMMU_CAP_INTR_REMAP:
-		return (irq_remapping_enabled == 1);
 	case IOMMU_CAP_NOEXEC:
 		return false;
 	case IOMMU_CAP_PRE_BOOT_PROTECTION:
@@ -3671,7 +3669,8 @@ int amd_iommu_create_irq_domain(struct amd_iommu *iommu)
 	}
 
 	irq_domain_update_bus_token(iommu->ir_domain,  DOMAIN_BUS_AMDVI);
-	iommu->ir_domain->flags |= IRQ_DOMAIN_FLAG_MSI_PARENT;
+	iommu->ir_domain->flags |= IRQ_DOMAIN_FLAG_MSI_PARENT |
+				   IRQ_DOMAIN_FLAG_ISOLATED_MSI;
 
 	if (amd_iommu_np_cache)
 		iommu->ir_domain->msi_parent_ops = &virt_amdvi_msi_parent_ops;

drivers/iommu/intel/iommu.c

@@ -4464,8 +4464,6 @@ static bool intel_iommu_capable(struct device *dev, enum iommu_cap cap)
 	switch (cap) {
 	case IOMMU_CAP_CACHE_COHERENCY:
 		return true;
-	case IOMMU_CAP_INTR_REMAP:
-		return irq_remapping_enabled == 1;
 	case IOMMU_CAP_PRE_BOOT_PROTECTION:
 		return dmar_platform_optin();
 	case IOMMU_CAP_ENFORCE_CACHE_COHERENCY:

drivers/iommu/intel/irq_remapping.c

@@ -573,7 +573,8 @@ static int intel_setup_irq_remapping(struct intel_iommu *iommu)
 	}
 
 	irq_domain_update_bus_token(iommu->ir_domain,  DOMAIN_BUS_DMAR);
-	iommu->ir_domain->flags |= IRQ_DOMAIN_FLAG_MSI_PARENT;
+	iommu->ir_domain->flags |= IRQ_DOMAIN_FLAG_MSI_PARENT |
+				   IRQ_DOMAIN_FLAG_ISOLATED_MSI;
 
 	if (cap_caching_mode(iommu->cap))
 		iommu->ir_domain->msi_parent_ops = &virt_dmar_msi_parent_ops;