netdev - Re: [PATCH 1/2] PCI: hv: enable pci_hyperv to allow dynamic vector allocation

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Message-ID: <20250417072943.GA20244@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
Date: Thu, 17 Apr 2025 00:29:43 -0700
From: Shradha Gupta <shradhagupta@...ux.microsoft.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>, linux-hyperv@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Nipun Gupta <nipun.gupta@....com>,
	Yury Norov <yury.norov@...il.com>, Jason Gunthorpe <jgg@...pe.ca>,
	Jonathan Cameron <Jonathan.Cameron@...ei.com>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Shivamurthy Shastri <shivamurthy.shastri@...utronix.de>,
	Kevin Tian <kevin.tian@...el.com>, Long Li <longli@...rosoft.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, Rob Herring <robh@...nel.org>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Krzysztof Wilczy??ski <kw@...ux.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Dexuan Cui <decui@...rosoft.com>, Wei Liu <wei.liu@...nel.org>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Konstantin Taranov <kotaranov@...rosoft.com>,
	Simon Horman <horms@...nel.org>, Leon Romanovsky <leon@...nel.org>,
	Maxim Levitsky <mlevitsk@...hat.com>,
	Erni Sri Satya Vennela <ernis@...ux.microsoft.com>,
	Peter Zijlstra <peterz@...radead.org>, netdev@...r.kernel.org,
	linux-rdma@...r.kernel.org, Paul Rosswurm <paulros@...rosoft.com>,
	Shradha Gupta <shradhagupta@...rosoft.com>
Subject: Re: [PATCH 1/2] PCI: hv: enable pci_hyperv to allow dynamic vector
 allocation

On Wed, Apr 16, 2025 at 01:30:42PM -0500, Bjorn Helgaas wrote:
> [+to Thomas]
> 
> On Wed, Apr 16, 2025 at 08:36:06AM -0700, Shradha Gupta wrote:
> > For supporting dynamic MSI vector allocation by pci controllers, enabling
> > the flag MSI_FLAG_PCI_MSIX_ALLOC_DYN is not enough, msix_prepare_msi_desc()
> > to prepare the desc is needed. Export pci_msix_prepare_desc() to allow pci
> > controllers like pci-hyperv to support dynamic MSI vector allocation.
> > Also, add the flag MSI_FLAG_PCI_MSIX_ALLOC_DYN and use
> > pci_msix_prepare_desc() in pci_hyperv controller
> 
> Follow capitalization convention for subject line.  Probably remove
> "pci_hyperv" since it already contains "PCI: hv" and add something
> about MSI-X.
> 
> s/pci/PCI/
> 
> s/MSI vector/MSI-X vector/ since the context says you're concerned
> with MSI-X.
> 
> This requires an ack from Thomas; moved him to "To:" line.
>
Thanks Bjorn. I will work on addressing these.

Regards,
Shradha. 
> > Signed-off-by: Shradha Gupta <shradhagupta@...ux.microsoft.com>
> > Reviewed-by: Haiyang Zhang <haiyangz@...rosoft.com>
> > Reviewed-by: Long Li <longli@...rosoft.com>
> > ---
> >  drivers/pci/controller/pci-hyperv.c | 7 +++++--
> >  drivers/pci/msi/irqdomain.c         | 5 +++--
> >  include/linux/msi.h                 | 2 ++
> >  3 files changed, 10 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> > index ac27bda5ba26..f2fa6bdb6bb8 100644
> > --- a/drivers/pci/controller/pci-hyperv.c
> > +++ b/drivers/pci/controller/pci-hyperv.c
> > @@ -598,7 +598,8 @@ static unsigned int hv_msi_get_int_vector(struct irq_data *data)
> >  	return cfg->vector;
> >  }
> >  
> > -#define hv_msi_prepare		pci_msi_prepare
> > +#define hv_msi_prepare			pci_msi_prepare
> > +#define hv_msix_prepare_desc		pci_msix_prepare_desc
> >  
> >  /**
> >   * hv_arch_irq_unmask() - "Unmask" the IRQ by setting its current
> > @@ -727,6 +728,7 @@ static void hv_arch_irq_unmask(struct irq_data *data)
> >  #define FLOW_HANDLER		NULL
> >  #define FLOW_NAME		NULL
> >  #define hv_msi_prepare		NULL
> > +#define hv_msix_prepare_desc	NULL
> >  
> >  struct hv_pci_chip_data {
> >  	DECLARE_BITMAP(spi_map, HV_PCI_MSI_SPI_NR);
> > @@ -2063,6 +2065,7 @@ static struct irq_chip hv_msi_irq_chip = {
> >  static struct msi_domain_ops hv_msi_ops = {
> >  	.msi_prepare	= hv_msi_prepare,
> >  	.msi_free	= hv_msi_free,
> > +	.prepare_desc	= hv_msix_prepare_desc,
> >  };
> >  
> >  /**
> > @@ -2084,7 +2087,7 @@ static int hv_pcie_init_irq_domain(struct hv_pcibus_device *hbus)
> >  	hbus->msi_info.ops = &hv_msi_ops;
> >  	hbus->msi_info.flags = (MSI_FLAG_USE_DEF_DOM_OPS |
> >  		MSI_FLAG_USE_DEF_CHIP_OPS | MSI_FLAG_MULTI_PCI_MSI |
> > -		MSI_FLAG_PCI_MSIX);
> > +		MSI_FLAG_PCI_MSIX | MSI_FLAG_PCI_MSIX_ALLOC_DYN);
> >  	hbus->msi_info.handler = FLOW_HANDLER;
> >  	hbus->msi_info.handler_name = FLOW_NAME;
> >  	hbus->msi_info.data = hbus;
> > diff --git a/drivers/pci/msi/irqdomain.c b/drivers/pci/msi/irqdomain.c
> > index d7ba8795d60f..43129aa6d6c7 100644
> > --- a/drivers/pci/msi/irqdomain.c
> > +++ b/drivers/pci/msi/irqdomain.c
> > @@ -222,13 +222,14 @@ static void pci_irq_unmask_msix(struct irq_data *data)
> >  	pci_msix_unmask(irq_data_get_msi_desc(data));
> >  }
> >  
> > -static void pci_msix_prepare_desc(struct irq_domain *domain, msi_alloc_info_t *arg,
> > -				  struct msi_desc *desc)
> > +void pci_msix_prepare_desc(struct irq_domain *domain, msi_alloc_info_t *arg,
> > +			   struct msi_desc *desc)
> >  {
> >  	/* Don't fiddle with preallocated MSI descriptors */
> >  	if (!desc->pci.mask_base)
> >  		msix_prepare_msi_desc(to_pci_dev(desc->dev), desc);
> >  }
> > +EXPORT_SYMBOL_GPL(pci_msix_prepare_desc);
> >  
> >  static const struct msi_domain_template pci_msix_template = {
> >  	.chip = {
> > diff --git a/include/linux/msi.h b/include/linux/msi.h
> > index 86e42742fd0f..d5864d5e75c2 100644
> > --- a/include/linux/msi.h
> > +++ b/include/linux/msi.h
> > @@ -691,6 +691,8 @@ struct irq_domain *pci_msi_create_irq_domain(struct fwnode_handle *fwnode,
> >  					     struct irq_domain *parent);
> >  u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev);
> >  struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev);
> > +void pci_msix_prepare_desc(struct irq_domain *domain, msi_alloc_info_t *arg,
> > +			   struct msi_desc *desc);
> >  #else /* CONFIG_PCI_MSI */
> >  static inline struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev)
> >  {
> > -- 
> > 2.34.1
> >