xen-devel.lists.xenproject.org archive mirror
 help / color / mirror / Atom feed
From: Julien Grall <julien.grall@arm.com>
To: Ben Sanda <Ben.Sanda@dornerworks.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: George Dunlap <george.dunlap@citrix.com>
Subject: Re: [PATCH 3/6] xentrace: P2M lookup suport for ARM platform
Date: Wed, 30 Mar 2016 19:38:52 +0100	[thread overview]
Message-ID: <56FC1D3C.4040407@arm.com> (raw)
In-Reply-To: <A2A949C387F3A54C9B4DAC2DCD2E9A85E3337CFF@Quimby.dw.local>

On 28/03/16 19:55, Ben Sanda wrote:
> Julien and George,

Hi Ben,

Sorry for the late answer.

> Thank you for the comments. I had one question I wanted to ask.
>
>> A DOMID_XEN page could be read only too. For instance, the meta-data
>> of the trace buffer is read-only (see t_info), we don't want a domain
>> to be able to overwrite them.
>
>> However, all the foreign page are mapped read-write. You will need to
>> rework the code to map a foreign domain (see
>> XENMAPSPACE_gmfn_foreign) to allow read-only foreign page (maybe by
>> adding a new p2m_type_t?).
>
> I understand what you are saying in general, but I'm not familiar
> enough with the Xen memory mapping system to know how to actually
> implement this. The p2m_type_t p2m_ram_ro exists, which I could assign
> to read-only pages, but I'm unsure as to how to detect whether a
> request is to a read only mapping or a read-write. The normal (non
> DOMID_XEN) p2m_lookup function normally does this by reading the root-
> level page tables and somehow extracting the mapping type from the
> lpae_t structure. Given that we are not looking up the page tables for
> non-translated addresses, I'm not sure where/how to find the correct
> mapping type. Can I still lookup the page table entries for the MFN
> address and extract the p2m_type_t the same way?

You can know if the page is writable by looking to the page field 
u.inuse.type_info (PGT_writable_page means the page is writable).

Regards,

-- 
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel

  reply	other threads:[~2016-03-30 18:38 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-16 20:51 [PATCH 0/6] xentrace/xenalyze support on ARM Benjamin Sanda
2016-03-16 20:51 ` [PATCH 1/6] Flask: Support for ARM xentrace Benjamin Sanda
2016-03-17 14:56   ` Julien Grall
2016-03-17 15:03   ` Julien Grall
2016-03-25 19:27   ` Konrad Rzeszutek Wilk
2016-03-28 15:52     ` Ben Sanda
2016-03-16 20:51 ` [PATCH 2/6] xenalyze: Support for ARM platform Benjamin Sanda
2016-03-16 20:59   ` Andrew Cooper
2016-03-17 10:39     ` George Dunlap
2016-03-16 20:51 ` [PATCH 3/6] xentrace: P2M lookup suport " Benjamin Sanda
2016-03-17 16:21   ` Julien Grall
2016-03-28 18:55     ` Ben Sanda
2016-03-30 18:38       ` Julien Grall [this message]
2016-03-16 20:51 ` [PATCH 4/6] xentrace: ARM platform DOMID_XEN mapping support Benjamin Sanda
2016-03-17 15:53   ` Julien Grall
2016-03-16 20:51 ` [PATCH 5/6] xentrace: Trace buffer support for ARM platform Benjamin Sanda
2016-03-16 20:51 ` [PATCH 6/6] xentrace: ARM platform timestamp support Benjamin Sanda
2016-03-25 19:31   ` Konrad Rzeszutek Wilk
2016-03-31 16:38     ` Stefano Stabellini
2016-03-31 16:44       ` Ben Sanda
2016-04-01 13:05         ` Stefano Stabellini
2016-03-17 15:00 ` [PATCH 0/6] xentrace/xenalyze support on ARM Julien Grall
2016-03-17 16:50   ` Ben Sanda
2016-03-17 17:01     ` Julien Grall
2016-03-17 17:04       ` Ben Sanda
2016-03-18 17:12         ` Wei Liu
2016-03-17 17:23 ` George Dunlap

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=56FC1D3C.4040407@arm.com \
    --to=julien.grall@arm.com \
    --cc=Ben.Sanda@dornerworks.com \
    --cc=george.dunlap@citrix.com \
    --cc=xen-devel@lists.xenproject.org \
    --subject='Re: [PATCH 3/6] xentrace: P2M lookup suport for ARM platform' \
    /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

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).