linux-kernel - Re: [PATCH] ACPI / scan: Make it clear that acpi_bus

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <15493777.FVIQvWOuf9@vostro.rjw.lan>
Date:	Mon, 18 Feb 2013 14:17:02 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Vasilis Liaskovitis <vasilis.liaskovitis@...fitbricks.com>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Toshi Kani <toshi.kani@...com>, Jiang Liu <liuj97@...il.com>,
	wency@...fujitsu.com
Subject: Re: [PATCH] ACPI / scan: Make it clear that acpi_bus_trim() cannot fail

On Monday, February 18, 2013 01:25:49 PM Vasilis Liaskovitis wrote:
> Hi,
> 
> On Thu, Jan 24, 2013 at 11:56:50PM +0100, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > 
> > Since acpi_bus_trim() cannot fail, change its definition to a void
> > function, so that its callers don't check the return value in vain
> > and update the callers.
> 
> I have missed a few patchsets/discussions in the last month and wanted to
> ask a question related to this: Does the new always-succeed 2-pass
> trim_device design guarantee safe memory hot-remove operations?

I doesn't by itself.  Nor it really can, because the .remove() callbacks of
device drivers are not allowed to fail.

> Afaict if memory offline fails now, the device is ejected (_EJ0) anyways
> causing a panic. Tested in a VM with linux-next-20130207 and
> linux-next-20130218 by doing an SCI-eject request on a hot-plugged dimm.
> 
> Are there more patches in development for safe memory hot-remove?

Yes, there are.  I sent a patch series yesterday introducing some safety
measures (you can disable memory hotplug from user space or disable
automatic ejection).  There's more to come still.

The plan is to introduce offline/online operations for memory modules (in
analogy with CPU core online/offline) that can be started by user space and
memory eject will only be possible after offline (i.e. when the memory module
is known to be not in use).

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/