Re: [PATCH 4/4] PCI: hv: Use the correct hypercall for unmasking interrupts on nested

Nuno Das Neves
2025-06-18T21:24:03Z

On 6/11/2025 4:07 PM, Michael Kelley wrote:
> From: Nuno Das Neves <nunodasneves@linux.microsoft.com> Sent: Tuesday, June 10, 2025 4:52 PM
>>
>> From: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
>>
>> Running as nested root on MSHV imposes a different requirement
>> for the pci-hyperv controller.
>>
>> In this setup, the interrupt will first come to the L1 (nested) hypervisor,
>> which will deliver it to the appropriate root CPU. Instead of issuing the
>> RETARGET hypercall, we should issue the MAP_DEVICE_INTERRUPT
>> hypercall to L1 to complete the setup.
>>
>> Rename hv_arch_irq_unmask() to hv_irq_retarget_interrupt().
>>
>> Co-developed-by: Jinank Jain <jinankjain@linux.microsoft.com>
>> Signed-off-by: Jinank Jain <jinankjain@linux.microsoft.com>
>> Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
>> Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
>> ---
>> drivers/pci/controller/pci-hyperv.c | 18 ++++++++++++++++--
>> 1 file changed, 16 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
>> index 4d25754dfe2f..0f491c802fb9 100644
>> --- a/drivers/pci/controller/pci-hyperv.c
>> +++ b/drivers/pci/controller/pci-hyperv.c
>> @@ -600,7 +600,7 @@ static unsigned int hv_msi_get_int_vector(struct irq_data *data)
>> #define hv_msi_prepare pci_msi_prepare
>>
>> /**
>> - * hv_arch_irq_unmask() - "Unmask" the IRQ by setting its current
>> + * hv_irq_retarget_interrupt() - "Unmask" the IRQ by setting its current
>> * affinity.
>> * @data: Describes the IRQ
>> *
>> @@ -609,7 +609,7 @@ static unsigned int hv_msi_get_int_vector(struct irq_data *data)
>> * is built out of this PCI bus's instance GUID and the function
>> * number of the device.
>> */
>> -static void hv_arch_irq_unmask(struct irq_data *data)
>> +static void hv_irq_retarget_interrupt(struct irq_data *data)
>> {
>> struct msi_desc *msi_desc = irq_data_get_msi_desc(data);
>> struct hv_retarget_device_interrupt *params;
>> @@ -714,6 +714,20 @@ static void hv_arch_irq_unmask(struct irq_data *data)
>> dev_err(&hbus->hdev->device,
>> "%s() failed: %#llx", __func__, res);
>> }
>> +
>> +static void hv_arch_irq_unmask(struct irq_data *data)
>> +{
>> + if (hv_nested && hv_root_partition())
>
> Based on Patch 1 of this series, this driver is not loaded for the root
> partition in the non-nested case. So testing hv_nested is redundant.
>

Good point, I'll change it to just check for hv_root_partition() here.

>> + /*
>> + * In case of the nested root partition, the nested hypervisor
>> + * is taking care of interrupt remapping and thus the
>> + * MAP_DEVICE_INTERRUPT hypercall is required instead of
>> + * RETARGET_INTERRUPT.
>> + */
>> + (void)hv_map_msi_interrupt(data, NULL);
>> + else
>> + hv_irq_retarget_interrupt(data);
>> +}
>> #elif defined(CONFIG_ARM64)
>> /*
>> * SPI vectors to use for vPCI; arch SPIs range is [32, 1019], but leaving a bit
>> --
>> 2.34.1