All of lore.kernel.org
 help / color / mirror / Atom feed
From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Keir Fraser <keir.fraser@eu.citrix.com>
Cc: "dan.magenheimer@oracle.com" <dan.magenheimer@oracle.com>,
	"Xen-Devel (E-mail)" <xen-devel@lists.xensource.com>
Subject: Re: Is exposing shared_info to user-land secure?
Date: Fri, 01 Aug 2008 13:35:23 -0700	[thread overview]
Message-ID: <4893738B.9060702@goop.org> (raw)
In-Reply-To: <C4B90575.1BBE5%keir.fraser@eu.citrix.com>

Keir Fraser wrote:
> I think it might be okay. One issue is that how to let the user-space
> process know what vcpu it is running on, so it can use the correct timestamp
> info in a way that is safe against preemption. Bear in mind that the user
> address space may be shared by multiple concurrent threads on different
> VCPUs! If you assume consistent-tsc across all CPUs then the task is easier,
> but I don't think we'll want to bake that assumption into guest kernels and
> their interface to user processes.
>   

x86-64 already exports the current cpu and nodeid in the limit of a gdt 
entry, so you can fetch it from userspace with lsl.

    J

  reply	other threads:[~2008-08-01 20:35 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-08-01 16:13 Is exposing shared_info to user-land secure? Dan Magenheimer
2008-08-01 17:24 ` Keir Fraser
2008-08-01 20:35   ` Jeremy Fitzhardinge [this message]
2008-08-01 20:31 ` Jeremy Fitzhardinge

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=4893738B.9060702@goop.org \
    --to=jeremy@goop.org \
    --cc=dan.magenheimer@oracle.com \
    --cc=keir.fraser@eu.citrix.com \
    --cc=xen-devel@lists.xensource.com \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.