Re: 3.16-rc2 WARNING: CPU: 0 PID: 0 at arch/x86/xen/multicalls.c:129 xen_mc_flush+0x1ab/0x1c0()

From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Sander Eikelenboom <linux@eikelenboom.it>
Cc: xen-devel@lists.xenproject.org, David Vrabel <david.vrabel@citrix.com>
Subject: Re: 3.16-rc2 WARNING: CPU: 0 PID: 0 at arch/x86/xen/multicalls.c:129 xen_mc_flush+0x1ab/0x1c0()
Date: Thu, 26 Jun 2014 12:16:43 -0400	[thread overview]
Message-ID: <53AC476B.1000305@oracle.com> (raw)
In-Reply-To: <1683024832.20140626135707@eikelenboom.it>

On 06/26/2014 07:57 AM, Sander Eikelenboom wrote:
> Hi,
>
> Got the warning below on dom0 boot with a 3.16-rc2 kernel, doesn't seem to do
> much immediate harm:
>
> [   12.723393] Calibrating delay loop (skipped), value calculated using timer frequency.. 6402.05 BogoMIPS (lpj=10667280)
> [   12.723414] pid_max: default: 32768 minimum: 301
> [   12.723433] ACPI: Core revision 20140424
> [   12.740681] ACPI: All ACPI Tables successfully acquired
> [   12.743145] ------------[ cut here ]------------
> [   12.743170] WARNING: CPU: 0 PID: 0 at arch/x86/xen/multicalls.c:129 xen_mc_flush+0x1ab/0x1c0()
> [   12.743186] Modules linked in:
> [   12.743196] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.16.0-rc2-20140626+ #1
> [   12.743209] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640)  , BIOS V1.8B1 09/13/2010
> [   12.743223]  0000000000000009 ffffffff82203d88 ffffffff81afdba7 ffffffff822184e0
> [   12.743242]  0000000000000000 ffffffff82203dc8 ffffffff810bfdb2 ffffffff81007858
> [   12.743261]  0000000000000000 0000000000000001 0000000000000000 ffff88005f60b120
> [   12.743280] Call Trace:
> [   12.743290]  [<ffffffff81afdba7>] dump_stack+0x46/0x58
> [   12.743302]  [<ffffffff810bfdb2>] warn_slowpath_common+0x82/0xb0
> [   12.743316]  [<ffffffff81007858>] ? pte_pfn_to_mfn+0x88/0xa0
> [   12.743328]  [<ffffffff810bfdf5>] warn_slowpath_null+0x15/0x20
> [   12.743341]  [<ffffffff81004b6b>] xen_mc_flush+0x1ab/0x1c0
> [   12.743353]  [<ffffffff810072fd>] xen_alloc_pte+0x1ad/0x220
> [   12.743364]  [<ffffffff8100886b>] ? xen_make_pte+0x1b/0x70
> [   12.743378]  [<ffffffff81014a6f>] init_espfix_ap+0x22f/0x3f0
> [   12.743392]  [<ffffffff8232079d>] init_espfix_bsp+0xee/0xf3
> [   12.743404]  [<ffffffff82317ffe>] start_kernel+0x3d6/0x441
> [   12.743416]  [<ffffffff82317a27>] ? set_init_arg+0x58/0x58
> [   12.743428]  [<ffffffff82317608>] x86_64_start_reservations+0x2a/0x2c
> [   12.743441]  [<ffffffff8231af8e>] xen_start_kernel+0x59b/0x59d
> [   12.743468] ---[ end trace 20d3292a87f35842 ]---
> [   12.743943] Dentry cache hash table entries: 262144 (order: 9, 2097152 bytes)
> [   12.744726] Inode-cache hash table entries: 131072 (order: 8, 1048576 bytes)
> [   12.745043] Mount-cache hash table entries: 4096 (order: 3, 32768 bytes)
> [   12.745064] Mountpoint-cache hash table entries: 4096 (order: 3, 32768 bytes)
> [   12.745709] Initializing cgroup subsys freezer
> [   12.745733] Initializing cgroup subsys blkio
>
> If you need more info / complete logs, give me a call.

This is caused by hpa's ESP fix for 16-bit programs leaking SP bits from 
64-bit kernels (commit 3891a04aafd668686239349ea58f3314ea2af86b).

It's harmless in the sense that the only effect is that the workaround 
won't get enabled.

-boris