From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH] intel-iommu: Synchronize gcmd value with global command register Date: Wed, 27 Mar 2013 11:31:22 +0100 Message-ID: <20130327103122.GK30540@8bytes.org> References: <1363829556-2128-1-git-send-email-indou.takao@jp.fujitsu.com> <20130326144629.GB2727@8bytes.org> <51527D74.9080209@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <51527D74.9080209-+CUm20s59erQFUHtdCDX3A@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Takao Indoh Cc: kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: iommu@lists.linux-foundation.org On Wed, Mar 27, 2013 at 02:02:44PM +0900, Takao Indoh wrote: > The root cause of this problem is mismatch between iommu->gcmd and > global command register in the case of kdump. At boot time, initial > value of iommu->gcmd is zero as I wrote above, but actual global command > register is *not* zero because some bits like IRE/TE/QIE are already set > in *first* kernel. Therefore this patch synchronize them to fix this > problem. Ok, I understand, but I still don't see why this is a problem. There is no point for the kdump kernel to preserve hardware state from the previous kernel. So I think the way it is implemented is correct. Joerg