linux-kernel - Re: [patch 19/33] genirq/msi: Provide msi_desc::msi

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Date:   Thu, 17 Nov 2022 09:48:45 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Marc Zyngier <maz@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dave Jiang <dave.jiang@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Ashok Raj <ashok.raj@...el.com>, Jon Mason <jdmason@...zu.us>,
        Allen Hubbe <allenbh@...il.com>,
        "Ahmed S. Darwish" <darwi@...utronix.de>,
        Reinette Chatre <reinette.chatre@...el.com>
Subject: Re: [patch 19/33] genirq/msi: Provide msi_desc::msi_data

On Wed, Nov 16 2022 at 15:28, Jason Gunthorpe wrote:
> On Fri, Nov 11, 2022 at 02:58:41PM +0100, Thomas Gleixner wrote:
>> +/**
>> + * struct msi_desc_data - Generic MSI descriptor data
>> + * @iobase:     Pointer to the IOMEM base adress for interrupt callbacks
>> + * @cookie:	Device cookie provided at allocation time
>> + *
>> + * The content of this data is implementation defined, e.g. PCI/IMS
>> + * implementations will define the meaning of the data.
>> + */
>> +struct msi_desc_data {
>> +	void			__iomem *iobase;
>> +	union msi_dev_cookie	cookie;
>> +};
>
> It would be nice to see the pci_msi_desc converted to a domain
> specific storage as well.
>
> Maybe could be written
>
> struct msi_desc {
>    u64 domain_data[2];
> }
>
> struct pci_msi_desc {
> 		u32 msi_mask;
> 		u8	multiple	: 3;
> 		u8	multi_cap	: 3;
> 		u8	can_mask	: 1;
> 		u8	is_64		: 1;
> 		u8	mask_pos;
> 		u16 default_irq;
> }
> static_assert(sizeof(struct pci_msi_desc) <= sizeof(((struct msi_desc *)0)->domain_data));
>
> struct pci_msix_desc {
> 		u32 msix_ctrl;
> 		u8	multiple	: 3;
> 		u8	multi_cap	: 3;
> 		u8	can_mask	: 1;
> 		u8	is_64		: 1;
> 		u16 default_irq;
> 		void __iomem *mask_base;
> }
> static_assert(sizeof(struct pci_msix_desc) <= sizeof(((struct msi_desc *)0)->domain_data));
>
> ideally hidden in the pci code with some irq_chip facing export API to
> snoop in the bits a few places need
>
> We've used 128 bits for the PCI descriptor, we might as well like
> everyone have all 128 bits for whatever they want to do

Not sure because we end up with nasty type casts for

> struct msi_desc {
>    u64 domain_data[2];
> }

Let me think about it.

Thanks,

        tglx