From: Juergen Gross <jgross@suse.com>
To: Alex Thorlton <athorlton@sgi.com>,
linux-kernel@vger.kernel.org, Jan Beulich <JBeulich@suse.com>
Cc: Russ Anderson <rja@sgi.com>,
David Vrabel <david.vrabel@citrix.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, xen-devel@lists.xenproject.org
Subject: Re: [RFC PATCH] xen/x86: Increase xen_e820_map to E820_X_MAX possible entries
Date: Tue, 15 Nov 2016 07:33:26 +0100 [thread overview]
Message-ID: <a03b2e71-cc6a-7f62-6c09-877c576fab80@suse.com> (raw)
In-Reply-To: <1479168677-23633-1-git-send-email-athorlton@sgi.com>
On 15/11/16 01:11, Alex Thorlton wrote:
> Hey everyone,
>
> We're having problems with large systems hitting a BUG in
> xen_memory_setup, due to extra e820 entries created in the
> XENMEM_machine_memory_map callback. The change in the patch gets things
> working, but Boris and I wanted to get opinions on whether or not this
> is the appropriate/entire solution, which is why I've sent it as an RFC
> for now.
>
> Boris pointed out to me that E820_X_MAX is only large when CONFIG_EFI=y,
> which is a detail worth discussig. He proposed possibly adding
> CONFIG_XEN to the conditions under which we set E820_X_MAX to a larger
> value than E820MAX, since the Xen e820 table isn't bound by the
> zero-page memory limitations.
>
> I do *slightly* question the use of E820_X_MAX here, only from a
> cosmetic prospective, as I believe this macro is intended to describe
> the maximum size of the extended e820 table, which, AFAIK, is not used
> by the Xen HV. That being said, there isn't exactly a "more
> appropriate" macro/variable to use, so this may not really be an issue.
>
> Any input on the patch, or the questions I've raised above is greatly
> appreciated!
While I think extending the e820 table is the right thing to do I'm
questioning the assumptions here.
Looking briefly through the Xen hypervisor sources I think it isn't
yet ready for such large machines: the hypervisor's e820 map seems to
be still limited to 128 e820 entries. Jan, did I overlook an EFI
specific path extending this limitation?
In case I'm right the Xen hypervisor should be prepared for a larger
e820 map, but this won't help alone as there would still be additional
entries for the IOAPICs created.
So I think we need something like:
#define E820_XEN_MAX (E820_X_MAX + MAX_IO_APICS)
and use this for sizing xen_e820_map[].
Juergen
next prev parent reply other threads:[~2016-11-15 6:33 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-15 0:11 [RFC PATCH] xen/x86: Increase xen_e820_map to E820_X_MAX possible entries Alex Thorlton
2016-11-15 6:33 ` Juergen Gross [this message]
2016-11-15 7:15 ` Jan Beulich
[not found] ` <582AC427020000780011EA7E@suse.com>
2016-11-15 7:36 ` Juergen Gross
2016-11-15 8:01 ` Jan Beulich
[not found] ` <582ACEDE020000780011EAC9@suse.com>
2016-11-15 8:42 ` Juergen Gross
2016-11-15 9:45 ` Jan Beulich
[not found] ` <582AE72D020000780011EBB2@suse.com>
2016-11-15 9:55 ` Juergen Gross
2016-11-15 10:44 ` Jan Beulich
[not found] ` <582AF51F020000780011ECB4@suse.com>
2016-11-15 11:07 ` Juergen Gross
2016-11-15 11:12 ` Jan Beulich
2016-11-15 15:22 ` Alex Thorlton
2016-11-16 6:06 ` Juergen Gross
2016-11-30 3:24 ` [RFC PATCH v2] " Alex Thorlton
2016-11-30 3:24 ` [PATCH 1/2] x86: Make E820_X_MAX unconditionally larger than E820MAX Alex Thorlton
2016-11-30 6:21 ` Ingo Molnar
2016-12-01 18:37 ` Alex Thorlton
2016-11-30 3:24 ` [PATCH 2/2] xen/x86: Increase xen_e820_map to E820_X_MAX possible entries Alex Thorlton
2016-11-30 5:18 ` Juergen Gross
2016-12-05 17:49 ` [RFC PATCH v3] " Alex Thorlton
2016-12-05 17:49 ` [PATCH 1/2] x86: Make E820_X_MAX unconditionally larger than E820MAX Alex Thorlton
2016-12-09 10:12 ` Juergen Gross
2016-12-05 17:49 ` [PATCH 2/2] xen/x86: Increase xen_e820_map to E820_X_MAX possible entries Alex Thorlton
2016-12-09 10:12 ` Juergen Gross
2016-12-08 5:50 ` [RFC PATCH v3] " Juergen Gross
2016-12-09 3:46 ` Ingo Molnar
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=a03b2e71-cc6a-7f62-6c09-877c576fab80@suse.com \
--to=jgross@suse.com \
--cc=JBeulich@suse.com \
--cc=athorlton@sgi.com \
--cc=david.vrabel@citrix.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=rja@sgi.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
--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).