xen-devel.lists.xenproject.org archive mirror
 help / color / mirror / Atom feed
From: Julien Grall <julien.grall@arm.com>
To: Stefano Stabellini <sstabellini@kernel.org>,
	xen-devel@lists.xenproject.org
Cc: Stefano Stabellini <stefanos@xilinx.com>
Subject: Re: [PATCH v2 10/10] xen/arm: add reserved-memory regions to the dom0 memory node
Date: Tue, 7 May 2019 21:15:16 +0100	[thread overview]
Message-ID: <1b8217e1-8671-e1e7-d5bc-4b4c144eedd6@arm.com> (raw)
In-Reply-To: <1556658172-8824-10-git-send-email-sstabellini@kernel.org>

Hi Stefano,

On 4/30/19 10:02 PM, Stefano Stabellini wrote:
> Reserved memory regions are automatically remapped to dom0. Their device
> tree nodes are also added to dom0 device tree. However, the dom0 memory
> node is not currently extended to cover the reserved memory regions
> ranges as required by the spec.  This commit fixes it.

AFAICT, this does not cover the problem mention by Amit in [1].

But I am still not happy with the approach taken for the reserved-memory 
regions in this series. As I pointed out before, they are just normal 
memory that was reserved for other purpose (CMA, framebuffer...).

Treating them as "device" from Xen POV is a clear abuse of the meaning 
and I don't believe it is a viable solution long term.

Indeed, some of the regions may have a property "reusable" allowing the 
the OS to use them until they are claimed by the device driver owning 
the region. I don't know how Linux (or any other OS) is using it today, 
but I don't see what would prevent it to use them as hypercall buffer. 
This would obviously not work because they are not actual RAM from Xen POV.

On a similar topic, because they are normal memory, I don't think 
XEN_DOMCTL_memory_mapping should be able to map reserved-regions. So the 
iomem rangeset should not contain them.

Cheers,

[1] <CABHD4K-z-x=3joJWcOb_x9m7zsjzhskDQweNBr+paLS=PFEY9Q@mail.gmail.com>

-- 
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

WARNING: multiple messages have this Message-ID (diff)
From: Julien Grall <julien.grall@arm.com>
To: Stefano Stabellini <sstabellini@kernel.org>,
	xen-devel@lists.xenproject.org
Cc: Stefano Stabellini <stefanos@xilinx.com>
Subject: Re: [Xen-devel] [PATCH v2 10/10] xen/arm: add reserved-memory regions to the dom0 memory node
Date: Tue, 7 May 2019 21:15:16 +0100	[thread overview]
Message-ID: <1b8217e1-8671-e1e7-d5bc-4b4c144eedd6@arm.com> (raw)
Message-ID: <20190507201516.YQWZ-Q1htX-b_zLQh7rP3d226JXuMF0CvvyOKcAnLis@z> (raw)
In-Reply-To: <1556658172-8824-10-git-send-email-sstabellini@kernel.org>

Hi Stefano,

On 4/30/19 10:02 PM, Stefano Stabellini wrote:
> Reserved memory regions are automatically remapped to dom0. Their device
> tree nodes are also added to dom0 device tree. However, the dom0 memory
> node is not currently extended to cover the reserved memory regions
> ranges as required by the spec.  This commit fixes it.

AFAICT, this does not cover the problem mention by Amit in [1].

But I am still not happy with the approach taken for the reserved-memory 
regions in this series. As I pointed out before, they are just normal 
memory that was reserved for other purpose (CMA, framebuffer...).

Treating them as "device" from Xen POV is a clear abuse of the meaning 
and I don't believe it is a viable solution long term.

Indeed, some of the regions may have a property "reusable" allowing the 
the OS to use them until they are claimed by the device driver owning 
the region. I don't know how Linux (or any other OS) is using it today, 
but I don't see what would prevent it to use them as hypercall buffer. 
This would obviously not work because they are not actual RAM from Xen POV.

On a similar topic, because they are normal memory, I don't think 
XEN_DOMCTL_memory_mapping should be able to map reserved-regions. So the 
iomem rangeset should not contain them.

Cheers,

[1] <CABHD4K-z-x=3joJWcOb_x9m7zsjzhskDQweNBr+paLS=PFEY9Q@mail.gmail.com>

-- 
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

  parent reply	other threads:[~2019-05-07 20:15 UTC|newest]

Thread overview: 86+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-30 21:02 [PATCH v2 0/10] iomem memory policy Stefano Stabellini
2019-04-30 21:02 ` [Xen-devel] " Stefano Stabellini
2019-04-30 21:02 ` [PATCH v2 01/10] xen: add a p2mt parameter to map_mmio_regions Stefano Stabellini
2019-04-30 21:02   ` [Xen-devel] " Stefano Stabellini
2019-05-02 14:59   ` Jan Beulich
2019-05-02 14:59     ` [Xen-devel] " Jan Beulich
2019-05-02 18:49     ` Stefano Stabellini
2019-05-02 18:49       ` [Xen-devel] " Stefano Stabellini
2019-05-15 13:39   ` Oleksandr
2019-05-15 13:39     ` [Xen-devel] " Oleksandr
2019-04-30 21:02 ` [PATCH v2 02/10] xen: rename un/map_mmio_regions to un/map_regions Stefano Stabellini
2019-04-30 21:02   ` [Xen-devel] " Stefano Stabellini
2019-05-01  9:22   ` Julien Grall
2019-05-01  9:22     ` [Xen-devel] " Julien Grall
2019-06-17 21:24     ` Stefano Stabellini
2019-06-18 11:05       ` Julien Grall
2019-06-18 20:19         ` Stefano Stabellini
2019-05-02 15:03   ` Jan Beulich
2019-05-02 15:03     ` [Xen-devel] " Jan Beulich
2019-05-02 18:55     ` Stefano Stabellini
2019-05-02 18:55       ` [Xen-devel] " Stefano Stabellini
2019-04-30 21:02 ` [PATCH v2 03/10] xen: extend XEN_DOMCTL_memory_mapping to handle memory policy Stefano Stabellini
2019-04-30 21:02   ` [Xen-devel] " Stefano Stabellini
2019-05-02 15:12   ` Jan Beulich
2019-05-02 15:12     ` [Xen-devel] " Jan Beulich
2019-06-17 21:28     ` Stefano Stabellini
2019-06-18  8:59       ` Jan Beulich
2019-06-18 20:32         ` Stefano Stabellini
2019-06-18 23:15           ` Stefano Stabellini
2019-06-19  6:53             ` Jan Beulich
2019-05-07 16:41   ` Julien Grall
2019-05-07 16:41     ` [Xen-devel] " Julien Grall
2019-06-17 22:43     ` Stefano Stabellini
2019-06-18 11:13       ` Julien Grall
2019-05-15 14:40   ` Oleksandr
2019-05-15 14:40     ` [Xen-devel] " Oleksandr
2019-04-30 21:02 ` [PATCH v2 04/10] libxc: introduce xc_domain_mem_map_policy Stefano Stabellini
2019-04-30 21:02   ` [Xen-devel] " Stefano Stabellini
2019-04-30 21:02 ` [PATCH v2 05/10] libxl/xl: add memory policy option to iomem Stefano Stabellini
2019-04-30 21:02   ` [Xen-devel] " Stefano Stabellini
2019-05-01  9:42   ` Julien Grall
2019-05-01  9:42     ` [Xen-devel] " Julien Grall
2019-06-17 22:32     ` Stefano Stabellini
2019-06-18 11:09       ` Julien Grall
2019-06-18 11:15   ` Julien Grall
2019-06-18 22:07     ` Stefano Stabellini
2019-06-18 22:20       ` Julien Grall
2019-06-18 22:46         ` Stefano Stabellini
2019-04-30 21:02 ` [PATCH v2 06/10] xen/arm: extend device_tree_for_each_node Stefano Stabellini
2019-04-30 21:02   ` [Xen-devel] " Stefano Stabellini
2019-05-07 17:12   ` Julien Grall
2019-05-07 17:12     ` [Xen-devel] " Julien Grall
2019-04-30 21:02 ` [PATCH v2 07/10] xen/arm: make process_memory_node a device_tree_node_func Stefano Stabellini
2019-04-30 21:02   ` [Xen-devel] " Stefano Stabellini
2019-05-01  9:47   ` Julien Grall
2019-05-01  9:47     ` [Xen-devel] " Julien Grall
2019-04-30 21:02 ` [PATCH v2 08/10] xen/arm: keep track of reserved-memory regions Stefano Stabellini
2019-04-30 21:02   ` [Xen-devel] " Stefano Stabellini
2019-05-01 10:03   ` Julien Grall
2019-05-01 10:03     ` [Xen-devel] " Julien Grall
2019-06-21 23:47     ` Stefano Stabellini
2019-05-07 17:21   ` Julien Grall
2019-05-07 17:21     ` [Xen-devel] " Julien Grall
2019-04-30 21:02 ` [PATCH v2 09/10] xen/arm: map reserved-memory regions as normal memory in dom0 Stefano Stabellini
2019-04-30 21:02   ` [Xen-devel] " Stefano Stabellini
2019-05-07 19:52   ` Julien Grall
2019-05-07 19:52     ` [Xen-devel] " Julien Grall
2019-04-30 21:02 ` [PATCH v2 10/10] xen/arm: add reserved-memory regions to the dom0 memory node Stefano Stabellini
2019-04-30 21:02   ` [Xen-devel] " Stefano Stabellini
2019-05-07 20:15   ` Julien Grall [this message]
2019-05-07 20:15     ` Julien Grall
2019-05-10 20:51     ` Stefano Stabellini
2019-05-10 20:51       ` [Xen-devel] " Stefano Stabellini
2019-05-10 21:43       ` Julien Grall
2019-05-10 21:43         ` [Xen-devel] " Julien Grall
2019-05-11 12:40         ` Julien Grall
2019-05-11 12:40           ` [Xen-devel] " Julien Grall
2019-05-20 21:26           ` Stefano Stabellini
2019-05-20 21:26             ` [Xen-devel] " Stefano Stabellini
2019-05-20 22:38             ` Julien Grall
2019-05-20 22:38               ` [Xen-devel] " Julien Grall
2019-06-05 16:30               ` Julien Grall
2019-06-21 23:47                 ` Stefano Stabellini
2019-05-16 16:52 ` [PATCH v2 0/10] iomem memory policy Oleksandr
2019-05-16 16:52   ` [Xen-devel] " Oleksandr
2019-06-21 23:48   ` Stefano Stabellini

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=1b8217e1-8671-e1e7-d5bc-4b4c144eedd6@arm.com \
    --to=julien.grall@arm.com \
    --cc=sstabellini@kernel.org \
    --cc=stefanos@xilinx.com \
    --cc=xen-devel@lists.xenproject.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).