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

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Message-ID:
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Date: Wed, 11 Jun 2025 23:07:40 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.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>
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Subject: RE: [PATCH 4/4] PCI: hv: Use the correct hypercall for unmasking
 interrupts on nested

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.

> +		/*
> +		 * 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