From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: Grant unmap error checking in Dom0 Date: Tue, 18 Mar 2014 09:38:34 -0400 Message-ID: <20140318133834.GC25364@phenom.dumpdata.com> References: <5328484E.5060701@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <5328484E.5060701@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Zoltan Kiss Cc: Ian Campbell , David Vrabel , xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On Tue, Mar 18, 2014 at 01:21:18PM +0000, Zoltan Kiss wrote: > Hi, > > Just out of curiosity I've checked how Dom0 handles errors during > grant unmapping. Usually there is a BUG_ON(ret) for the return value > of gnttab_unmap_refs in blkback and netback, gntdev drops just a > WARN. > The return value can be non-zero only if Xen failed to copy the map > operations back and forth to the guest supplied memory, so it's > reasonable to crash there. However I'm wondering why gntdev is happy > with just a WARN. > Another thing, we don't check the status of the operations if the > return value is zero. We shouldn't normally do that, Xen logs info > messages in some cases, but not always (e.g. XSM or IOMMU problems). > For debugging purposes however it could be useful to have the > ability to turn on checking in Dom0. A quick and dirty way to do > this is to use printk_get_level to figure out if the loglevel is > e.g. KERN_NOTICE or lower, but I'm sure there is a better way to do > this :) It would be an overkill to introduce new config option, I'm > thinking a runtime parameter to check in an unlikely(), so it won't > cause performance penalty for normal operation. Any opinions on > that? One can always just have printk(KERN_DEBUG and if the user did not boot with 'debug' the messages go to /dev/null. > > Zoli > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel