From: Alex Thorlton <athorlton@sgi.com>
To: linux-kernel@vger.kernel.org
Cc: Alex Thorlton <athorlton@sgi.com>, Russ Anderson <rja@sgi.com>,
        David Vrabel <david.vrabel@citrix.com>,
        Juergen Gross <jgross@suse.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: [RFC PATCH] xen/x86: Increase xen_e820_map to E820_X_MAX possible entries
Date: Mon, 14 Nov 2016 18:11:16 -0600
Message-Id: <1479168677-23633-1-git-send-email-athorlton@sgi.com>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1272
Lines: 34

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!

- Alex

Alex Thorlton (1):
  xen/x86: Increase xen_e820_map to E820_X_MAX possible entries

 arch/x86/xen/setup.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

-- 
1.8.5.6