Message-ID: <20250529132015.GD27681@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
Date: Thu, 29 May 2025 06:20:15 -0700
From: Shradha Gupta <shradhagupta@...ux.microsoft.com>
To: Saurabh Singh Sengar <ssengar@...ux.microsoft.com>
Cc: 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>,
	Michael Kelley <mhklinux@...look.com>, 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>,
	Kevin Tian <kevin.tian@...el.com>, Long Li <longli@...rosoft.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Bjorn Helgaas <bhelgaas@...gle.com>, Rob Herring <robh@...nel.org>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Krzysztof Wilczy???~Dski <kw@...ux.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>, netdev@...r.kernel.org,
	linux-rdma@...r.kernel.org, Paul Rosswurm <paulros@...rosoft.com>,
	Shradha Gupta <shradhagupta@...rosoft.com>
Subject: Re: [PATCH v4 5/5] net: mana: Allocate MSI-X vectors dynamically

On Wed, May 28, 2025 at 08:45:20PM -0700, Saurabh Singh Sengar wrote:
> On Tue, May 27, 2025 at 08:59:03AM -0700, Shradha Gupta wrote:
> > Currently, the MANA driver allocates MSI-X vectors statically based on
> > MANA_MAX_NUM_QUEUES and num_online_cpus() values and in some cases ends
> > up allocating more vectors than it needs. This is because, by this time
> > we do not have a HW channel and do not know how many IRQs should be
> > allocated.
> > 
> > To avoid this, we allocate 1 MSI-X vector during the creation of HWC and
> > after getting the value supported by hardware, dynamically add the
> > remaining MSI-X vectors.
> > 
> > Signed-off-by: Shradha Gupta <shradhagupta@...ux.microsoft.com>
> > Reviewed-by: Haiyang Zhang <haiyangz@...rosoft.com>
> > ---
> >  Changes in v4:
> >  * added BUG_ON at appropriate places
> >  * moved xa_destroy to mana_gd_remove()
> >  * rearragned the cleanup logic in mana_gd_setup_dyn_irqs()
> >  * simplified processing around start_irq_index in mana_gd_setup_irqs()
> >  * return 0 instead of return err as appropriate
> > ---
> >  Changes in v3:
> >  * implemented irq_contexts as xarrays rather than list
> >  * split the patch to create a perparation patch around irq_setup()
> >  * add log when IRQ allocation/setup for remaining IRQs fails
> > ---
> >  Changes in v2:
> >  * Use string 'MSI-X vectors' instead of 'pci vectors'
> >  * make skip-cpu a bool instead of int
> >  * rearrange the comment arout skip_cpu variable appropriately
> >  * update the capability bit for driver indicating dynamic IRQ allocation
> >  * enforced max line length to 80
> >  * enforced RCT convention
> >  * initialized gic to NULL, for when there is a possibility of gic
> >    not being populated correctly
> > ---
> >  .../net/ethernet/microsoft/mana/gdma_main.c   | 306 +++++++++++++-----
> >  include/net/mana/gdma.h                       |   8 +-
> >  2 files changed, 235 insertions(+), 79 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > index 763a548c4a2b..98ebecbec9a7 100644
> > --- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > +++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > @@ -6,6 +6,8 @@
> >  #include <linux/pci.h>
> >  #include <linux/utsname.h>
> >  #include <linux/version.h>
> > +#include <linux/msi.h>
> > +#include <linux/irqdomain.h>
> >  
> >  #include <net/mana/mana.h>
> >  
> > @@ -80,8 +82,15 @@ static int mana_gd_query_max_resources(struct pci_dev *pdev)
> >  		return err ? err : -EPROTO;
> >  	}
> >  
> > -	if (gc->num_msix_usable > resp.max_msix)
> > -		gc->num_msix_usable = resp.max_msix;
> > +	if (!pci_msix_can_alloc_dyn(pdev)) {
> > +		if (gc->num_msix_usable > resp.max_msix)
> > +			gc->num_msix_usable = resp.max_msix;
> > +	} else {
> > +		/* If dynamic allocation is enabled we have already allocated
> > +		 * hwc msi
> > +		 */
> > +		gc->num_msix_usable = min(resp.max_msix, num_online_cpus() + 1);
> > +	}
> >  
> >  	if (gc->num_msix_usable <= 1)
> >  		return -ENOSPC;
> > @@ -482,7 +491,9 @@ static int mana_gd_register_irq(struct gdma_queue *queue,
> >  	}
> >  
> >  	queue->eq.msix_index = msi_index;
> > -	gic = &gc->irq_contexts[msi_index];
> > +	gic = xa_load(&gc->irq_contexts, msi_index);
> > +	if (WARN_ON(!gic))
> > +		return -EINVAL;
> >  
> >  	spin_lock_irqsave(&gic->lock, flags);
> >  	list_add_rcu(&queue->entry, &gic->eq_list);
> > @@ -507,7 +518,10 @@ static void mana_gd_deregiser_irq(struct gdma_queue *queue)
> >  	if (WARN_ON(msix_index >= gc->num_msix_usable))
> >  		return;
> >  
> > -	gic = &gc->irq_contexts[msix_index];
> > +	gic = xa_load(&gc->irq_contexts, msix_index);
> > +	if (WARN_ON(!gic))
> > +		return;
> > +
> >  	spin_lock_irqsave(&gic->lock, flags);
> >  	list_for_each_entry_rcu(eq, &gic->eq_list, entry) {
> >  		if (queue == eq) {
> > @@ -1366,47 +1380,113 @@ static int irq_setup(unsigned int *irqs, unsigned int len, int node,
> >  	return 0;
> >  }
> >  
> > -static int mana_gd_setup_irqs(struct pci_dev *pdev)
> > +static int mana_gd_setup_dyn_irqs(struct pci_dev *pdev, int nvec)
> >  {
> >  	struct gdma_context *gc = pci_get_drvdata(pdev);
> > -	unsigned int max_queues_per_port;
> >  	struct gdma_irq_context *gic;
> > -	unsigned int max_irqs, cpu;
> > -	int start_irq_index = 1;
> > -	int nvec, *irqs, irq;
> > -	int err, i = 0, j;
> > +	bool skip_first_cpu = false;
> > +	int *irqs, irq, err, i;
> >  
> >  	cpus_read_lock();
> 
> Now that num_online_cpus is moved further down in this new logic,
> do we want to reduce the critical section ?
> 
> I don't think we want kmalloc_array to be protected.
> 
> 
> > -	max_queues_per_port = num_online_cpus();
> > -	if (max_queues_per_port > MANA_MAX_NUM_QUEUES)
> > -		max_queues_per_port = MANA_MAX_NUM_QUEUES;
> >  
> > -	/* Need 1 interrupt for the Hardware communication Channel (HWC) */
> > -	max_irqs = max_queues_per_port + 1;
> > -
> > -	nvec = pci_alloc_irq_vectors(pdev, 2, max_irqs, PCI_IRQ_MSIX);
> > -	if (nvec < 0) {
> > -		cpus_read_unlock();
> > -		return nvec;
> > -	}
> > -	if (nvec <= num_online_cpus())
> > -		start_irq_index = 0;
> > -
> > -	irqs = kmalloc_array((nvec - start_irq_index), sizeof(int), GFP_KERNEL);
> > +	irqs = kmalloc_array(nvec, sizeof(int), GFP_KERNEL);
> >  	if (!irqs) {
> >  		err = -ENOMEM;
> >  		goto free_irq_vector;
> >  	}
> >  
> > -	gc->irq_contexts = kcalloc(nvec, sizeof(struct gdma_irq_context),
> > -				   GFP_KERNEL);
> > -	if (!gc->irq_contexts) {
> > +	/*
> > +	 * While processing the next pci irq vector, we start with index 1,
> > +	 * as IRQ vector at index 0 is already processed for HWC.
> > +	 * However, the population of irqs array starts with index 0, to be
> > +	 * further used in irq_setup()
> > +	 */
> > +	for (i = 1; i <= nvec; i++) {
> > +		gic = kzalloc(sizeof(*gic), GFP_KERNEL);
> > +		if (!gic) {
> > +			err = -ENOMEM;
> > +			goto free_irq;
> > +		}
> > +		gic->handler = mana_gd_process_eq_events;
> > +		INIT_LIST_HEAD(&gic->eq_list);
> > +		spin_lock_init(&gic->lock);
> > +
> > +		snprintf(gic->name, MANA_IRQ_NAME_SZ, "mana_q%d@pci:%s",
> > +			 i - 1, pci_name(pdev));
> > +
> > +		/* one pci vector is already allocated for HWC */
> > +		irqs[i - 1] = pci_irq_vector(pdev, i);
> > +		if (irqs[i - 1] < 0) {
> > +			err = irqs[i - 1];
> > +			goto free_current_gic;
> > +		}
> > +
> > +		err = request_irq(irqs[i - 1], mana_gd_intr, 0, gic->name, gic);
> > +		if (err)
> > +			goto free_current_gic;
> > +
> > +		xa_store(&gc->irq_contexts, i, gic, GFP_KERNEL);
> > +	}
> > +
> > +	/*
> > +	 * When calling irq_setup() for dynamically added IRQs, if number of
> > +	 * CPUs is more than or equal to allocated MSI-X, we need to skip the
> > +	 * first CPU sibling group since they are already affinitized to HWC IRQ
> > +	 */
> > +	if (gc->num_msix_usable <= num_online_cpus())
> > +		skip_first_cpu = true;
> > +
> > +	err = irq_setup(irqs, nvec, gc->numa_node, skip_first_cpu);
> > +	if (err)
> > +		goto free_irq;
> > +
> > +	cpus_read_unlock();
> > +	kfree(irqs);
> > +	return 0;
> > +
> > +free_current_gic:
> > +	kfree(gic);
> > +free_irq:
> > +	for (i -= 1; i > 0; i--) {
> > +		irq = pci_irq_vector(pdev, i);
> > +		gic = xa_load(&gc->irq_contexts, i);
> > +		if (WARN_ON(!gic))
> > +			continue;
> > +
> > +		irq_update_affinity_hint(irq, NULL);
> > +		free_irq(irq, gic);
> > +		xa_erase(&gc->irq_contexts, i);
> > +		kfree(gic);
> > +	}
> > +	kfree(irqs);
> > +free_irq_vector:
> > +	cpus_read_unlock();
> > +	return err;
> > +}
> > +
> > +static int mana_gd_setup_irqs(struct pci_dev *pdev, int nvec)
> > +{
> > +	struct gdma_context *gc = pci_get_drvdata(pdev);
> > +	struct gdma_irq_context *gic;
> > +	int *irqs, *start_irqs, irq;
> > +	unsigned int cpu;
> > +	int err, i;
> > +
> > +	cpus_read_lock();
> 
> Same here
> 
> > +	irqs = kmalloc_array(nvec, sizeof(int), GFP_KERNEL);
> > +	if (!irqs) {
> >  		err = -ENOMEM;
> > -		goto free_irq_array;
> > +		goto free_irq_vector;
> >  	}
> >  
> >  	for (i = 0; i < nvec; i++) {
> > -		gic = &gc->irq_contexts[i];
> > +		gic = kzalloc(sizeof(*gic), GFP_KERNEL);
> > +		if (!gic) {
> > +			err = -ENOMEM;
> > +			goto free_irq;
> > +		}
> > +
> >  		gic->handler = mana_gd_process_eq_events;
> >  		INIT_LIST_HEAD(&gic->eq_list);
> >  		spin_lock_init(&gic->lock);
> 
> <snip>
> 
> - Saurabh

Thanks Saurabh, will get these too

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