linux-kernel - Re: [PATCH RFC v2 02/18] irq/dev-msi: Add support for a new DEV

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Date:   Tue, 21 Jul 2020 13:13:44 -0300
From:   Jason Gunthorpe <jgg@...lanox.com>
To:     Dave Jiang <dave.jiang@...el.com>
Cc:     vkoul@...nel.org, megha.dey@...el.com, maz@...nel.org,
        bhelgaas@...gle.com, rafael@...nel.org, gregkh@...uxfoundation.org,
        tglx@...utronix.de, hpa@...or.com, alex.williamson@...hat.com,
        jacob.jun.pan@...el.com, ashok.raj@...el.com, yi.l.liu@...el.com,
        baolu.lu@...el.com, kevin.tian@...el.com, sanjay.k.kumar@...el.com,
        tony.luck@...el.com, jing.lin@...el.com, dan.j.williams@...el.com,
        kwankhede@...dia.com, eric.auger@...hat.com, parav@...lanox.com,
        dave.hansen@...el.com, netanelg@...lanox.com, shahafs@...lanox.com,
        yan.y.zhao@...ux.intel.com, pbonzini@...hat.com,
        samuel.ortiz@...el.com, mona.hossain@...el.com,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-pci@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH RFC v2 02/18] irq/dev-msi: Add support for a new DEV_MSI
 irq domain

On Tue, Jul 21, 2020 at 09:02:28AM -0700, Dave Jiang wrote:
> From: Megha Dey <megha.dey@...el.com>
> 
> Add support for the creation of a new DEV_MSI irq domain. It creates a
> new irq chip associated with the DEV_MSI domain and adds the necessary
> domain operations to it.
> 
> Add a new config option DEV_MSI which must be enabled by any
> driver that wants to support device-specific message-signaled-interrupts
> outside of PCI-MSI(-X).
> 
> Lastly, add device specific mask/unmask callbacks in addition to a write
> function to the platform_msi_ops.
> 
> Reviewed-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Megha Dey <megha.dey@...el.com>
> Signed-off-by: Dave Jiang <dave.jiang@...el.com>
>  arch/x86/include/asm/hw_irq.h |    5 ++
>  drivers/base/Kconfig          |    7 +++
>  drivers/base/Makefile         |    1 
>  drivers/base/dev-msi.c        |   95 +++++++++++++++++++++++++++++++++++++++++
>  drivers/base/platform-msi.c   |   45 +++++++++++++------
>  drivers/base/platform-msi.h   |   23 ++++++++++
>  include/linux/msi.h           |    8 +++
>  7 files changed, 168 insertions(+), 16 deletions(-)
>  create mode 100644 drivers/base/dev-msi.c
>  create mode 100644 drivers/base/platform-msi.h
> 
> diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
> index 74c12437401e..8ecd7570589d 100644
> +++ b/arch/x86/include/asm/hw_irq.h
> @@ -61,6 +61,11 @@ struct irq_alloc_info {
>  			irq_hw_number_t	msi_hwirq;
>  		};
>  #endif
> +#ifdef CONFIG_DEV_MSI
> +		struct {
> +			irq_hw_number_t hwirq;
> +		};
> +#endif

Why is this in this patch? I didn't see an obvious place where it is
used?
>  
> +static void __platform_msi_desc_mask_unmask_irq(struct msi_desc *desc, u32 mask)
> +{
> +	const struct platform_msi_ops *ops;
> +
> +	ops = desc->platform.msi_priv_data->ops;
> +	if (!ops)
> +		return;
> +
> +	if (mask) {
> +		if (ops->irq_mask)
> +			ops->irq_mask(desc);
> +	} else {
> +		if (ops->irq_unmask)
> +			ops->irq_unmask(desc);
> +	}
> +}
> +
> +void platform_msi_mask_irq(struct irq_data *data)
> +{
> +	__platform_msi_desc_mask_unmask_irq(irq_data_get_msi_desc(data), 1);
> +}
> +
> +void platform_msi_unmask_irq(struct irq_data *data)
> +{
> +	__platform_msi_desc_mask_unmask_irq(irq_data_get_msi_desc(data), 0);
> +}

This is a bit convoluted, just call the op directly:

void platform_msi_unmask_irq(struct irq_data *data)
{
	const struct platform_msi_ops *ops = desc->platform.msi_priv_data->ops;

	if (ops->irq_unmask)
		ops->irq_unmask(desc);
}

> diff --git a/include/linux/msi.h b/include/linux/msi.h
> index 7f6a8eb51aca..1da97f905720 100644
> +++ b/include/linux/msi.h
> @@ -323,9 +323,13 @@ enum {
>  
>  /*
>   * platform_msi_ops - Callbacks for platform MSI ops
> + * @irq_mask:   mask an interrupt source
> + * @irq_unmask: unmask an interrupt source
>   * @write_msg:	write message content
>   */
>  struct platform_msi_ops {
> +	unsigned int            (*irq_mask)(struct msi_desc *desc);
> +	unsigned int            (*irq_unmask)(struct msi_desc *desc);

Why do these functions return things if the only call site throws it
away?

Jason