linux-kernel - Re: [PATCH v3 2/2] PCI: hv: Refactor hv_irq_unmask() to use cpumask_to

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Message-ID: <20190227142820.GA16315@e107981-ln.cambridge.arm.com>
Date:   Wed, 27 Feb 2019 14:28:20 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     Maya Nakamura <m.maya.nakamura@...il.com>,
        linux-kernel@...r.kernel.org,
        driverdev-devel@...uxdriverproject.org, haiyangz@...rosoft.com,
        marcelo.cerri@...onical.com, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, kys@...rosoft.com,
        sthemmin@...rosoft.com, olaf@...fle.de, apw@...onical.com,
        jasowang@...hat.com, mikelley@...rosoft.com,
        Alexander.Levin@...rosoft.com
Subject: Re: [PATCH v3 2/2] PCI: hv: Refactor hv_irq_unmask() to use
 cpumask_to_vpset()

On Wed, Feb 27, 2019 at 01:34:44PM +0100, Vitaly Kuznetsov wrote:
> Maya Nakamura <m.maya.nakamura@...il.com> writes:
> 
> > Remove the duplicate implementation of cpumask_to_vpset() and use the
> > shared implementation. Export hv_max_vp_index, which is required by
> > cpumask_to_vpset().
> >
> > Apply changes to hv_irq_unmask() based on feedback.
> >
> 
> I just noticed an issue with this patch, sorry I've missed it before. I
> don't see the commit in Linus' tree, not sure if we should amend this
> one or a follow-up patch is needed.

I will drop this patch from the PCI queue, it does not make sense
to merge a patch adding a bug and fix it up later with a subsequent
one given that it is not upstream yet.

Lorenzo

> > Signed-off-by: Maya Nakamura <m.maya.nakamura@...il.com>
> > ---
> > Changes in v3:
> >  - Modify to catch all failures from cpumask_to_vpset().
> >  - Correct the v2 change log about the commit message.
> >
> > Changes in v2:
> >  - Remove unnecessary nr_bank initialization.
> >  - Delete two unnecessary dev_err()'s.
> >  - Unlock before returning.
> >  - Update the commit message.
> >
> >  arch/x86/hyperv/hv_init.c           |  1 +
> >  drivers/pci/controller/pci-hyperv.c | 38 +++++++++++++----------------
> >  2 files changed, 18 insertions(+), 21 deletions(-)
> >
> > diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> > index 7abb09e2eeb8..7f2eed1fc81b 100644
> > --- a/arch/x86/hyperv/hv_init.c
> > +++ b/arch/x86/hyperv/hv_init.c
> > @@ -96,6 +96,7 @@ void  __percpu **hyperv_pcpu_input_arg;
> >  EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
> >  
> >  u32 hv_max_vp_index;
> > +EXPORT_SYMBOL_GPL(hv_max_vp_index);
> >  
> >  static int hv_cpu_init(unsigned int cpu)
> >  {
> > diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> > index da8b58d8630d..a78def332bbc 100644
> > --- a/drivers/pci/controller/pci-hyperv.c
> > +++ b/drivers/pci/controller/pci-hyperv.c
> > @@ -391,8 +391,6 @@ struct hv_interrupt_entry {
> >  	u32	data;
> >  };
> >  
> > -#define HV_VP_SET_BANK_COUNT_MAX	5 /* current implementation limit */
> > -
> >  /*
> >   * flags for hv_device_interrupt_target.flags
> >   */
> > @@ -908,12 +906,12 @@ static void hv_irq_unmask(struct irq_data *data)
> >  	struct retarget_msi_interrupt *params;
> >  	struct hv_pcibus_device *hbus;
> >  	struct cpumask *dest;
> > +	cpumask_var_t tmp;
> >  	struct pci_bus *pbus;
> >  	struct pci_dev *pdev;
> >  	unsigned long flags;
> >  	u32 var_size = 0;
> > -	int cpu_vmbus;
> > -	int cpu;
> > +	int cpu, nr_bank;
> >  	u64 res;
> >  
> >  	dest = irq_data_get_effective_affinity_mask(data);
> > @@ -953,29 +951,27 @@ static void hv_irq_unmask(struct irq_data *data)
> >  		 */
> >  		params->int_target.flags |=
> >  			HV_DEVICE_INTERRUPT_TARGET_PROCESSOR_SET;
> > -		params->int_target.vp_set.valid_bank_mask =
> > -			(1ull << HV_VP_SET_BANK_COUNT_MAX) - 1;
> > +
> > +		if (!alloc_cpumask_var(&tmp, GFP_KERNEL)) {
> 
> We can't use GFP_KERNEL here: this is happening under
> hbus->retarget_msi_interrupt_lock spinlock, we should use GFP_ATOMIC
> instead. It may, however, make sense to add the cpumask to a
> pre-allocated structure (e.g. struct hv_pcibus_device) to make sure the
> allocation never fails.
> 
> > +			res = 1;
> > +			goto exit_unlock;
> > +		}
> > +
> > +		cpumask_and(tmp, dest, cpu_online_mask);
> > +		nr_bank = cpumask_to_vpset(&params->int_target.vp_set, tmp);
> > +		free_cpumask_var(tmp);
> > +
> > +		if (nr_bank <= 0) {
> > +			res = 1;
> > +			goto exit_unlock;
> > +		}
> >  
> >  		/*
> >  		 * var-sized hypercall, var-size starts after vp_mask (thus
> >  		 * vp_set.format does not count, but vp_set.valid_bank_mask
> >  		 * does).
> >  		 */
> > -		var_size = 1 + HV_VP_SET_BANK_COUNT_MAX;
> > -
> > -		for_each_cpu_and(cpu, dest, cpu_online_mask) {
> > -			cpu_vmbus = hv_cpu_number_to_vp_number(cpu);
> > -
> > -			if (cpu_vmbus >= HV_VP_SET_BANK_COUNT_MAX * 64) {
> > -				dev_err(&hbus->hdev->device,
> > -					"too high CPU %d", cpu_vmbus);
> > -				res = 1;
> > -				goto exit_unlock;
> > -			}
> > -
> > -			params->int_target.vp_set.bank_contents[cpu_vmbus / 64]	|=
> > -				(1ULL << (cpu_vmbus & 63));
> > -		}
> > +		var_size = 1 + nr_bank;
> >  	} else {
> >  		for_each_cpu_and(cpu, dest, cpu_online_mask) {
> >  			params->int_target.vp_mask |=
> 
> -- 
> Vitaly