linux-kernel - RE: [PATCH 2/2] Drivers: hv: Compare cpumasks and not their weights in init_vp

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Message-ID: <MWHPR21MB1593EB66675B0EF8ADA3F580D7229@MWHPR21MB1593.namprd21.prod.outlook.com>
Date:   Fri, 28 Jan 2022 14:57:23 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     vkuznets <vkuznets@...hat.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        Wei Liu <wei.liu@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>
Subject: RE: [PATCH 2/2] Drivers: hv: Compare cpumasks and not their weights
 in init_vp_index()

From: Vitaly Kuznetsov <vkuznets@...hat.com> Sent: Friday, January 28, 2022 2:34 AM
> 
> The condition is supposed to check whether 'allocated_mask' got fully
> exhausted, i.e. there's no free CPU on the NUMA node left so we have
> to use one of the already used CPUs. As only bits which correspond
> to CPUs from 'cpumask_of_node(numa_node)' get set in 'allocated_mask',
> checking for the equal weights is technically correct but not obvious.
> Let's compare cpumasks directly.
> 
> No functional change intended.
> 
> Suggested-by: Michael Kelley <mikelley@...rosoft.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> ---
>  drivers/hv/channel_mgmt.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index 52cf6ae525e9..26d269ba947c 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -762,8 +762,7 @@ static void init_vp_index(struct vmbus_channel *channel)
>  		}
>  		allocated_mask = &hv_context.hv_numa_map[numa_node];
> 
> -		if (cpumask_weight(allocated_mask) ==
> -		    cpumask_weight(cpumask_of_node(numa_node))) {
> +		if (cpumask_equal(allocated_mask, cpumask_of_node(numa_node)))
> {
>  			/*
>  			 * We have cycled through all the CPUs in the node;
>  			 * reset the allocated map.
> --
> 2.34.1

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>