linux-kernel - Re: [PATCH v6 02/46] virtio: use u32, not bitmap for features

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Date:	Fri, 28 Nov 2014 13:44:57 +0100
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	linux-kernel@...r.kernel.org, David Miller <davem@...emloft.net>,
	rusty@....ibm.com, nab@...ux-iscsi.org, pbonzini@...hat.com,
	thuth@...ux.vnet.ibm.com, dahi@...ux.vnet.ibm.com,
	Rusty Russell <rusty@...tcorp.com.au>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Amit Shah <amit.shah@...hat.com>,
	Ohad Ben-Cohen <ohad@...ery.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	linux390@...ibm.com, Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Ashutosh Dixit <ashutosh.dixit@...el.com>,
	Nikhil Rao <nikhil.rao@...el.com>,
	Siva Yerramreddy <yshivakrishna@...il.com>,
	Joel Stanley <joel@....id.au>,
	virtualization@...ts.linux-foundation.org, lguest@...ts.ozlabs.org,
	linux-s390@...r.kernel.org
Subject: Re: [PATCH v6 02/46] virtio: use u32, not bitmap for features

On Thu, 27 Nov 2014 22:07:41 +0200
"Michael S. Tsirkin" <mst@...hat.com> wrote:

> It seemed like a good idea to use bitmap for features
> in struct virtio_device, but it's actually a pain,
> and seems to become even more painful when we get more
> than 32 feature bits.  Just change it to a u32 for now.
> 
> Based on patch by Rusty.
> 
> Suggested-by: David Hildenbrand <dahi@...ux.vnet.ibm.com>
> Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
> Signed-off-by: Cornelia Huck <cornelia.huck@...ibm.com>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>

> diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
> index d34ebfa..ab95a4c 100644
> --- a/drivers/virtio/virtio_pci.c
> +++ b/drivers/virtio/virtio_pci.c
> @@ -120,8 +120,7 @@ static void vp_finalize_features(struct virtio_device *vdev)
>  	vring_transport_features(vdev);
> 
>  	/* We only support 32 feature bits. */

I think you can kill this comment...

> -	BUILD_BUG_ON(ARRAY_SIZE(vdev->features) != 1);
> -	iowrite32(vdev->features[0], vp_dev->ioaddr+VIRTIO_PCI_GUEST_FEATURES);
> +	iowrite32(vdev->features, vp_dev->ioaddr+VIRTIO_PCI_GUEST_FEATURES);

...and add blanks around '+', as you're touching this line anyway.

>  }
> 
>  /* virtio config->get() implementation */

Reviewed-by: Cornelia Huck <cornelia.huck@...ibm.com>

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