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

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Message-ID: <5dbd2057-6b0d-45f0-8cf7-935509d4fb03@linux.microsoft.com>
Date: Wed, 18 Jun 2025 14:24:01 -0700
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
To: Michael Kelley <mhklinux@...look.com>,
 "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
 "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Cc: "kys@...rosoft.com" <kys@...rosoft.com>,
 "haiyangz@...rosoft.com" <haiyangz@...rosoft.com>,
 "wei.liu@...nel.org" <wei.liu@...nel.org>,
 "decui@...rosoft.com" <decui@...rosoft.com>,
 "catalin.marinas@....com" <catalin.marinas@....com>,
 "will@...nel.org" <will@...nel.org>, "tglx@...utronix.de"
 <tglx@...utronix.de>, "mingo@...hat.com" <mingo@...hat.com>,
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Subject: Re: [PATCH 4/4] PCI: hv: Use the correct hypercall for unmasking
 interrupts on nested

On 6/11/2025 4:07 PM, Michael Kelley wrote:
> From: Nuno Das Neves <nunodasneves@...ux.microsoft.com> Sent: Tuesday, June 10, 2025 4:52 PM
>>
>> From: Stanislav Kinsburskii <skinsburskii@...ux.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@...ux.microsoft.com>
>> Signed-off-by: Jinank Jain <jinankjain@...ux.microsoft.com>
>> Signed-off-by: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
>> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.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