linux-kernel - RE: [PATCH V4 08/11] vfio/pci: Use bitfield for struct vfio_pci_core

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Message-ID: <BN9PR11MB52768311F5FA320283B06C358C6B9@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Fri, 28 Apr 2023 06:43:00 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     "Chatre, Reinette" <reinette.chatre@...el.com>,
        "jgg@...dia.com" <jgg@...dia.com>,
        "yishaih@...dia.com" <yishaih@...dia.com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>
CC:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "darwi@...utronix.de" <darwi@...utronix.de>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        "Liu, Jing2" <jing2.liu@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "tom.zanussi@...ux.intel.com" <tom.zanussi@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH V4 08/11] vfio/pci: Use bitfield for struct
 vfio_pci_core_device flags

> From: Chatre, Reinette <reinette.chatre@...el.com>
> Sent: Friday, April 28, 2023 1:36 AM
> 
> struct vfio_pci_core_device contains eleven boolean flags.
> Boolean flags clearly indicate their usage but space usage
> starts to be a concern when there are many.
> 
> An upcoming change adds another boolean flag to
> struct vfio_pci_core_device, thereby increasing the concern
> that the boolean flags are consuming unnecessary space.
> 
> Transition the boolean flags to use bitfields. On a system that
> uses one byte per boolean this reduces the space consumed
> by existing flags from 11 bytes to 2 bytes with room for
> a few more flags without increasing the structure's size.
> 
> Suggested-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Reinette Chatre <reinette.chatre@...el.com>

Reviewed-by: Kevin Tian <kevin.tian@...el.com>