From: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Date: Thu, 17 Nov 2022 12:11:39 -0800
Patch-mainline: v6.2-rc1
Subject: iommu/hyper-v: Allow hyperv irq remapping without x2apic
Git-commit: fea858dc5d901626e5d794037b5bff9f59b9ded7
References: git-fixes
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>
Acked-by: Olaf Hering <ohering@suse.de>
---
arch/x86/kernel/cpu/mshyperv.c | 6 +++++
drivers/iommu/Kconfig | 6 ++---
drivers/iommu/hyperv-iommu.c | 11 ++++++---
3 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -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)
{
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -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"
diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-iommu.c
--- a/drivers/iommu/hyperv-iommu.c
+++ b/drivers/iommu/hyperv-iommu.c
@@ -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 = {