linux-kernel - Re: [RFC 1/2] virtio_console: Add support for DMA memory allocation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 5 Sep 2012 15:00:20 +0200
From:	Sjur Brændeland <sjurbren@...il.com>
To:	Rusty Russell <rusty@...tcorp.com.au>,
	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Amit Shah <amit.shah@...hat.com>, linux-kernel@...r.kernel.org,
	Ohad Ben-Cohen <ohad@...ery.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	virtualization@...ts.linux-foundation.org,
	Sjur Brændeland <sjur.brandeland@...ricsson.com>
Subject: Re: [RFC 1/2] virtio_console: Add support for DMA memory allocation

> The driver certainly shouldn't offer VIRTIO_CONSOLE_F_DMA_MEM if you
> don't have DMA!

OK, so the feature table could be done like this:

 static unsigned int features[] = {
	VIRTIO_CONSOLE_F_SIZE,
	VIRTIO_CONSOLE_F_MULTIPORT,
#if VIRTIO_CONSOLE_HAS_DMA
	VIRTIO_CONSOLE_F_DMA_MEM,
#endif
}

If the device then asks for VIRTIO_CONSOLE_F_DMA_MEM
when DMA is not supported, virtio will do BUG_ON() from
virtio_check_driver_offered_feature().

Is this acceptable or should we add a check in virtcons_probe()
and let the probing fail instead?

E.g:
	/* Refuse to bind if F_DMA_MEM request cannot be met */
	if (!VIRTIO_CONSOLE_HAS_DMA &&
	    (vdev->config->get_features(vdev) & (1 << VIRTIO_CONSOLE_F_DMA_MEM))){
		dev_err(&vdev->dev,
			"DMA_MEM requested, but arch does not support DMA\n");
		err = -EINVAL;
		goto fail;
	}

Regards,
Sjur
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/