Commit fea858dc authored by Nuno Das Neves's avatar Nuno Das Neves Committed by Wei Liu
Browse files

iommu/hyper-v: Allow hyperv irq remapping without x2apic 



If x2apic is not available, hyperv-iommu skips remapping
irqs. This breaks root partition which always needs irqs
remapped.

Fix this by allowing irq remapping regardless of x2apic,
and change hyperv_enable_irq_remapping() to return
IRQ_REMAP_XAPIC_MODE in case x2apic is missing.

Tested with root and non-root hyperv partitions.

Signed-off-by: default avatarNuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: default avatarTianyu Lan <Tianyu.Lan@microsoft.com>
Reviewed-by: default avatarMichael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1668715899-8971-1-git-send-email-nunodasneves@linux.microsoft.com


Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
parent 0408f16b

arch/x86/kernel/cpu/mshyperv.c

+6 −0
Original line number Diff line number Diff line
@@ -475,6 +475,12 @@ static bool __init ms_hyperv_x2apic_available(void) 
 * (logically) generates MSIs directly to the system APIC irq domain.

 * There is no HPET, and PCI MSI/MSI-X interrupts are remapped by the

 * pci-hyperv host bridge.

 *

 * Note: for a Hyper-V root partition, this will always return false.

 * The hypervisor doesn't expose these HYPERV_CPUID_VIRT_STACK_* cpuids by

 * default, they are implemented as intercepts by the Windows Hyper-V stack.

 * Even a nested root partition (L2 root) will not get them because the

 * nested (L1) hypervisor filters them out.

 */

static bool __init ms_hyperv_msi_ext_dest_id(void)

{

drivers/iommu/Kconfig

+3 −3
Original line number Diff line number Diff line
@@ -474,13 +474,13 @@ config QCOM_IOMMU 
	  Support for IOMMU on certain Qualcomm SoCs.



config HYPERV_IOMMU

	bool "Hyper-V x2APIC IRQ Handling"

	bool "Hyper-V IRQ Handling"

	depends on HYPERV && X86

	select IOMMU_API

	default HYPERV

	help

	  Stub IOMMU driver to handle IRQs as to allow Hyper-V Linux

	  guests to run with x2APIC mode enabled.

	  Stub IOMMU driver to handle IRQs to support Hyper-V Linux

	  guest and root partitions.



config VIRTIO_IOMMU

	tristate "Virtio IOMMU driver"

drivers/iommu/hyperv-iommu.c

+8 −3
Original line number Diff line number Diff line
@@ -122,9 +122,12 @@ static int __init hyperv_prepare_irq_remapping(void) 
	const char *name;

	const struct irq_domain_ops *ops;



	/*

	 * For a Hyper-V root partition, ms_hyperv_msi_ext_dest_id()

	 * will always return false.

	 */

	if (!hypervisor_is_type(X86_HYPER_MS_HYPERV) ||

	    x86_init.hyper.msi_ext_dest_id() ||

	    !x2apic_supported())

	    x86_init.hyper.msi_ext_dest_id())

		return -ENODEV;



	if (hv_root_partition) {
@@ -170,7 +173,9 @@ static int __init hyperv_prepare_irq_remapping(void) 


static int __init hyperv_enable_irq_remapping(void)

{

	if (x2apic_supported())

		return IRQ_REMAP_X2APIC_MODE;

	return IRQ_REMAP_XAPIC_MODE;

}



struct irq_remap_ops hyperv_irq_remap_ops = {