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

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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: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1668715899-8971-1-git-send-email-nunodasneves@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
This commit is contained in:
Nuno Das Neves 2022-11-17 12:11:39 -08:00 committed by Wei Liu
parent 0408f16b43
commit fea858dc5d
3 changed files with 17 additions and 6 deletions
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6
arch/x86/kernel/cpu/mshyperv.c
View File

@ -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)
{

6
drivers/iommu/Kconfig
View File

@ -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"

11
drivers/iommu/hyperv-iommu.c
View File

@ -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)
{
return IRQ_REMAP_X2APIC_MODE;
if (x2apic_supported())
return IRQ_REMAP_X2APIC_MODE;
return IRQ_REMAP_XAPIC_MODE;
}
struct irq_remap_ops hyperv_irq_remap_ops = {