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

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Date:   Wed, 27 Feb 2019 13:34:44 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Maya Nakamura <m.maya.nakamura@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        driverdev-devel@...uxdriverproject.org, haiyangz@...rosoft.com,
        marcelo.cerri@...onical.com, lorenzo.pieralisi@....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()

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.

> 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