linux-block.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Paolo Bonzini <pbonzini@redhat.com>
To: "Юрий Каменев" <damtev@yandex-team.ru>,
	"Stefan Hajnoczi" <stefanha@redhat.com>
Cc: "mst@redhat.com" <mst@redhat.com>,
	"jasowang@redhat.com" <jasowang@redhat.com>,
	"axboe@kernel.dk" <axboe@kernel.dk>,
	"virtualization@lists.linux-foundation.org" 
	<virtualization@lists.linux-foundation.org>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 1/1] virtio: disable partitions scanning for no partitions block
Date: Mon, 24 May 2021 21:41:01 +0200	[thread overview]
Message-ID: <21b08ea7-71c6-1b4b-3833-1c51d0e1d310@redhat.com> (raw)
In-Reply-To: <90021621883891@mail.yandex-team.ru>

On 24/05/21 21:34, Юрий Каменев wrote:
> Hi
> 
>     Is your goal to avoid accidentally detecting partitions because it's
>     confusing when that happens?
> 
> The main goal is reducing the kernel start time. It might be use useful 
> in tiny systems that use, for example, squashfs images with certainly no 
> partitions. Disabling partitions scanning for these images can save a 
> few tens of milliseconds which can be a significant acceleration for 
> starting such systems.

Perhaps that could be configured in the image, for example in the kernel 
command line?

Paolo

> 24.05.2021, 17:29, "Stefan Hajnoczi" <stefanha@redhat.com>:
> 
>     On Thu, May 20, 2021 at 04:39:08PM +0300, Yury Kamenev wrote:
> 
>     Hi,
>     Is there a VIRTIO spec change for the new VIRTIO_BLK_F_NO_PS feature
>     bit? Please send one:
>     https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=virtio#feedback
>     <https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=virtio#feedback>
> 
>     GENHD_FL_NO_PART_SCAN is not used much in other drivers. This makes me
>     wonder if the same use case is addressed through other means with SCSI,
>     NVMe, etc devices. Maybe Christoph or Jens can weigh in on whether
>     adding a bit to disable partition scanning for a virtio-blk fits into
>     the big picture?
> 
>     Is your goal to avoid accidentally detecting partitions because it's
>     confusing when that happens?
> 
>     VIRTIO is currently undergoing auditing and changes to support untrusted
>     devices. From that perspective adding a device feature bit to disable
>     partition scanning does not help protect the guest from an untrusted
>     disk. The guest cannot trust the device, instead the guest itself would
>     need to be configured to avoid partition scanning of untrusted devices.
> 
>     Stefan
> 
>           Signed-off-by: Yury Kamenev <damtev@yandex-team.ru
>         <mailto:damtev@yandex-team.ru>>
>           ---
>            drivers/block/virtio_blk.c | 6 ++++++
>            include/uapi/linux/virtio_blk.h | 1 +
>            2 files changed, 7 insertions(+)
> 
>           diff --git a/drivers/block/virtio_blk.c
>         b/drivers/block/virtio_blk.c
>           index b9fa3ef5b57c..17edcfee2208 100644
>           --- a/drivers/block/virtio_blk.c
>           +++ b/drivers/block/virtio_blk.c
>           @@ -799,6 +799,10 @@ static int virtblk_probe(struct
>         virtio_device *vdev)
>                    vblk->disk->flags |= GENHD_FL_EXT_DEVT;
>                    vblk->index = index;
> 
>           + /*Disable partitions scanning for no-partitions block*/
> 
> 
>     Formatting cleanup and rephrasing:
> 
>        /* Disable partition scanning for devices with no partitions */
> 
>           + if (virtio_has_feature(vdev, VIRTIO_BLK_F_NO_PS))
> 
> 
>     I suggest user a more obvious name:
> 
>        VIRTIO_BLK_F_NO_PART_SCAN
> 
>           + vblk->disk->flags |= GENHD_FL_NO_PART_SCAN;
>           +
>                    /* configure queue flush support */
>                    virtblk_update_cache_mode(vdev);
> 
>           @@ -977,6 +981,7 @@ static unsigned int features_legacy[] = {
>                    VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE,
>                    VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_TOPOLOGY,
>         VIRTIO_BLK_F_CONFIG_WCE,
>                    VIRTIO_BLK_F_MQ, VIRTIO_BLK_F_DISCARD,
>         VIRTIO_BLK_F_WRITE_ZEROES,
>           + VIRTIO_BLK_F_NO_PS,
>            }
>            ;
>            static unsigned int features[] = {
>           @@ -984,6 +989,7 @@ static unsigned int features[] = {
>                    VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE,
>                    VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_TOPOLOGY,
>         VIRTIO_BLK_F_CONFIG_WCE,
>                    VIRTIO_BLK_F_MQ, VIRTIO_BLK_F_DISCARD,
>         VIRTIO_BLK_F_WRITE_ZEROES,
>           + VIRTIO_BLK_F_NO_PS,
>            };
> 
>            static struct virtio_driver virtio_blk = {
>           diff --git a/include/uapi/linux/virtio_blk.h
>         b/include/uapi/linux/virtio_blk.h
>           index d888f013d9ff..f197d07afb05 100644
>           --- a/include/uapi/linux/virtio_blk.h
>           +++ b/include/uapi/linux/virtio_blk.h
>           @@ -40,6 +40,7 @@
>            #define VIRTIO_BLK_F_MQ 12 /* support more than one vq */
>            #define VIRTIO_BLK_F_DISCARD 13 /* DISCARD is supported */
>            #define VIRTIO_BLK_F_WRITE_ZEROES 14 /* WRITE ZEROES is
>         supported */
>           +#define VIRTIO_BLK_F_NO_PS 16 /* No partitions */
> 
>            /* Legacy feature bits */
>            #ifndef VIRTIO_BLK_NO_LEGACY
>           --
>           2.24.3 (Apple Git-128)
> 


  parent reply	other threads:[~2021-05-24 19:41 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-20 13:39 [PATCH 0/1] virtio: disable partitions scanning for no partitions block Yury Kamenev
2021-05-20 13:39 ` [PATCH 1/1] " Yury Kamenev
2021-05-24 14:29   ` Stefan Hajnoczi
2021-05-24 14:56     ` Christoph Hellwig
2021-05-24 16:25       ` Ulf Hansson
     [not found]     ` <90021621883891@mail.yandex-team.ru>
2021-05-24 19:41       ` Paolo Bonzini [this message]
2021-05-25 12:00         ` Iurii Kamenev
2021-07-15  9:47 [PATCH 0/1] " Yury Kamenev
2021-07-15  9:47 ` [PATCH 1/1] " Yury Kamenev
2021-07-15 11:22   ` Paolo Bonzini
2021-07-16  1:09   ` kernel test robot
2021-07-16  2:57   ` Jason Wang

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=21b08ea7-71c6-1b4b-3833-1c51d0e1d310@redhat.com \
    --to=pbonzini@redhat.com \
    --cc=axboe@kernel.dk \
    --cc=damtev@yandex-team.ru \
    --cc=hch@lst.de \
    --cc=jasowang@redhat.com \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mst@redhat.com \
    --cc=stefanha@redhat.com \
    --cc=virtualization@lists.linux-foundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).