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Message-ID: <ebccacdd-9ece-2831-fc22-9868dd1c4ea6@intel.com>
Date: Thu, 27 Aug 2020 17:24:42 -0700
From: "Dey, Megha" <megha.dey@...el.com>
To: Thomas Gleixner <tglx@...utronix.de>,
LKML <linux-kernel@...r.kernel.org>
CC: <x86@...nel.org>, Joerg Roedel <joro@...tes.org>,
<iommu@...ts.linux-foundation.org>, <linux-hyperv@...r.kernel.org>,
"Haiyang Zhang" <haiyangz@...rosoft.com>,
Jon Derrick <jonathan.derrick@...el.com>,
Lu Baolu <baolu.lu@...ux.intel.com>,
Wei Liu <wei.liu@...nel.org>,
"K. Y. Srinivasan" <kys@...rosoft.com>,
Stephen Hemminger <sthemmin@...rosoft.com>,
Steve Wahl <steve.wahl@....com>,
Dimitri Sivanich <sivanich@....com>,
"Russ Anderson" <rja@....com>, <linux-pci@...r.kernel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
<xen-devel@...ts.xenproject.org>, Juergen Gross <jgross@...e.com>,
"Boris Ostrovsky" <boris.ostrovsky@...cle.com>,
Stefano Stabellini <sstabellini@...nel.org>,
Marc Zyngier <maz@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Jason Gunthorpe <jgg@...lanox.com>,
Dave Jiang <dave.jiang@...el.com>,
Alex Williamson <alex.williamson@...hat.com>,
Jacob Pan <jacob.jun.pan@...el.com>,
Baolu Lu <baolu.lu@...el.com>,
Kevin Tian <kevin.tian@...el.com>,
Dan Williams <dan.j.williams@...el.com>
Subject: Re: [patch V2 29/46] irqdomain/msi: Allow to override
msi_domain_alloc/free_irqs()
Hi Thomas,
On 8/26/2020 4:16 AM, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@...utronix.de>
>
> To support MSI irq domains which do not fit at all into the regular MSI
> irqdomain scheme, like the XEN MSI interrupt management for PV/HVM/DOM0,
> it's necessary to allow to override the alloc/free implementation.
>
> This is a preperatory step to switch X86 away from arch_*_msi_irqs() and
> store the irq domain pointer right in struct device.
>
> No functional change for existing MSI irq domain users.
>
> Aside of the evil XEN wrapper this is also useful for special MSI domains
> which need to do extra alloc/free work before/after calling the generic
> core function. Work like allocating/freeing MSI descriptors, MSI storage
> space etc.
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
>
> ---
> include/linux/msi.h | 27 ++++++++++++++++++++
> kernel/irq/msi.c | 70 +++++++++++++++++++++++++++++++++++-----------------
> 2 files changed, 75 insertions(+), 22 deletions(-)
>
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -241,6 +241,10 @@ struct msi_domain_info;
> * @msi_finish: Optional callback to finalize the allocation
> * @set_desc: Set the msi descriptor for an interrupt
> * @handle_error: Optional error handler if the allocation fails
> + * @domain_alloc_irqs: Optional function to override the default allocation
> + * function.
> + * @domain_free_irqs: Optional function to override the default free
> + * function.
> *
> * @get_hwirq, @msi_init and @msi_free are callbacks used by
> * msi_create_irq_domain() and related interfaces
> @@ -248,6 +252,22 @@ struct msi_domain_info;
> * @msi_check, @msi_prepare, @msi_finish, @set_desc and @handle_error
> * are callbacks used by msi_domain_alloc_irqs() and related
> * interfaces which are based on msi_desc.
> + *
> + * @domain_alloc_irqs, @domain_free_irqs can be used to override the
> + * default allocation/free functions (__msi_domain_alloc/free_irqs). This
> + * is initially for a wrapper around XENs seperate MSI universe which can't
> + * be wrapped into the regular irq domains concepts by mere mortals. This
> + * allows to universally use msi_domain_alloc/free_irqs without having to
> + * special case XEN all over the place.
> + *
> + * Contrary to other operations @domain_alloc_irqs and @domain_free_irqs
> + * are set to the default implementation if NULL and even when
> + * MSI_FLAG_USE_DEF_DOM_OPS is not set to avoid breaking existing users and
> + * because these callbacks are obviously mandatory.
> + *
> + * This is NOT meant to be abused, but it can be useful to build wrappers
> + * for specialized MSI irq domains which need extra work before and after
> + * calling __msi_domain_alloc_irqs()/__msi_domain_free_irqs().
> */
> struct msi_domain_ops {
> irq_hw_number_t (*get_hwirq)(struct msi_domain_info *info,
> @@ -270,6 +290,10 @@ struct msi_domain_ops {
> struct msi_desc *desc);
> int (*handle_error)(struct irq_domain *domain,
> struct msi_desc *desc, int error);
> + int (*domain_alloc_irqs)(struct irq_domain *domain,
> + struct device *dev, int nvec);
> + void (*domain_free_irqs)(struct irq_domain *domain,
> + struct device *dev);
> };
>
> /**
> @@ -327,8 +351,11 @@ int msi_domain_set_affinity(struct irq_d
> struct irq_domain *msi_create_irq_domain(struct fwnode_handle *fwnode,
> struct msi_domain_info *info,
> struct irq_domain *parent);
> +int __msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
> + int nvec);
> int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
> int nvec);
> +void __msi_domain_free_irqs(struct irq_domain *domain, struct device *dev);
> void msi_domain_free_irqs(struct irq_domain *domain, struct device *dev);
> struct msi_domain_info *msi_get_domain_info(struct irq_domain *domain);
>
> --- a/kernel/irq/msi.c
> +++ b/kernel/irq/msi.c
> @@ -229,11 +229,13 @@ static int msi_domain_ops_check(struct i
> }
>
> static struct msi_domain_ops msi_domain_ops_default = {
> - .get_hwirq = msi_domain_ops_get_hwirq,
> - .msi_init = msi_domain_ops_init,
> - .msi_check = msi_domain_ops_check,
> - .msi_prepare = msi_domain_ops_prepare,
> - .set_desc = msi_domain_ops_set_desc,
> + .get_hwirq = msi_domain_ops_get_hwirq,
> + .msi_init = msi_domain_ops_init,
> + .msi_check = msi_domain_ops_check,
> + .msi_prepare = msi_domain_ops_prepare,
> + .set_desc = msi_domain_ops_set_desc,
> + .domain_alloc_irqs = __msi_domain_alloc_irqs,
> + .domain_free_irqs = __msi_domain_free_irqs,
> };
>
> static void msi_domain_update_dom_ops(struct msi_domain_info *info)
> @@ -245,6 +247,14 @@ static void msi_domain_update_dom_ops(st
> return;
> }
>
> + if (ops->domain_alloc_irqs == NULL)
> + ops->domain_alloc_irqs = msi_domain_ops_default.domain_alloc_irqs;
> + if (ops->domain_free_irqs == NULL)
> + ops->domain_free_irqs = msi_domain_ops_default.domain_free_irqs;
> +
> + if (!(info->flags & MSI_FLAG_USE_DEF_DOM_OPS))
> + return;
> +
> if (ops->get_hwirq == NULL)
> ops->get_hwirq = msi_domain_ops_default.get_hwirq;
> if (ops->msi_init == NULL)
> @@ -278,8 +288,7 @@ struct irq_domain *msi_create_irq_domain
> {
> struct irq_domain *domain;
>
> - if (info->flags & MSI_FLAG_USE_DEF_DOM_OPS)
> - msi_domain_update_dom_ops(info);
> + msi_domain_update_dom_ops(info);
> if (info->flags & MSI_FLAG_USE_DEF_CHIP_OPS)
> msi_domain_update_chip_ops(info);
>
> @@ -386,17 +395,8 @@ static bool msi_check_reservation_mode(s
> return desc->msi_attrib.is_msix || desc->msi_attrib.maskbit;
> }
>
> -/**
> - * msi_domain_alloc_irqs - Allocate interrupts from a MSI interrupt domain
> - * @domain: The domain to allocate from
> - * @dev: Pointer to device struct of the device for which the interrupts
> - * are allocated
> - * @nvec: The number of interrupts to allocate
> - *
> - * Returns 0 on success or an error code.
> - */
> -int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
> - int nvec)
> +int __msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
> + int nvec)
> {
> struct msi_domain_info *info = domain->host_data;
> struct msi_domain_ops *ops = info->ops;
> @@ -490,12 +490,24 @@ int msi_domain_alloc_irqs(struct irq_dom
> }
>
> /**
> - * msi_domain_free_irqs - Free interrupts from a MSI interrupt @domain associated tp @dev
> - * @domain: The domain to managing the interrupts
> + * msi_domain_alloc_irqs - Allocate interrupts from a MSI interrupt domain
> + * @domain: The domain to allocate from
> * @dev: Pointer to device struct of the device for which the interrupts
> - * are free
> + * are allocated
> + * @nvec: The number of interrupts to allocate
> + *
> + * Returns 0 on success or an error code.
> */
> -void msi_domain_free_irqs(struct irq_domain *domain, struct device *dev)
> +int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
> + int nvec)
> +{
> + struct msi_domain_info *info = domain->host_data;
> + struct msi_domain_ops *ops = info->ops;
> +
> + return ops->domain_alloc_irqs(domain, dev, nvec);
> +}
> +
Since, our upcoming driver will directly call this API, an
EXPORT_SYMBOL_GPL tag would be required.
Currently there is no use case. I was wondering if we should add this
change while submitting the
idxd/ims patches or would you add this to this patch?
> +void __msi_domain_free_irqs(struct irq_domain *domain, struct device *dev)
> {
> struct msi_desc *desc;
>
> @@ -513,6 +525,20 @@ void msi_domain_free_irqs(struct irq_dom
> }
>
> /**
> + * __msi_domain_free_irqs - Free interrupts from a MSI interrupt @domain associated tp @dev
> + * @domain: The domain to managing the interrupts
> + * @dev: Pointer to device struct of the device for which the interrupts
> + * are free
> + */
> +void msi_domain_free_irqs(struct irq_domain *domain, struct device *dev)
> +{
> + struct msi_domain_info *info = domain->host_data;
> + struct msi_domain_ops *ops = info->ops;
> +
> + return ops->domain_free_irqs(domain, dev);
> +}
> +
> +/**
> * msi_get_domain_info - Get the MSI interrupt domain info for @domain
> * @domain: The interrupt domain to retrieve data from
> *
>
>
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