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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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