From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH] xen/arm: Blacklist the memory mapped timer (armv7-timer-mem) Date: Wed, 14 Jan 2015 16:03:53 +0000 Message-ID: <54B69369.6000707@linaro.org> References: <1421179673-30754-1-git-send-email-julien.grall@linaro.org> <1421233321.19103.215.camel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YBQQi-0001dE-1k for xen-devel@lists.xenproject.org; Wed, 14 Jan 2015 16:04:24 +0000 Received: by mail-we0-f173.google.com with SMTP id q58so9648983wes.4 for ; Wed, 14 Jan 2015 08:04:22 -0800 (PST) In-Reply-To: <1421233321.19103.215.camel@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: Ian Campbell Cc: xen-devel@lists.xenproject.org, tim@xen.org, stefano.stabellini@citrix.com List-Id: xen-devel@lists.xenproject.org Hi Ian, On 14/01/15 11:02, Ian Campbell wrote: > On Tue, 2015-01-13 at 20:07 +0000, Julien Grall wrote: >> Some platform (such as the VFP Base AEMv8 model) has a memory mapped >> timer. We don't want DOM0 use this timer rather than the generic ARM >> timer. So blacklist it for all platforms. > > It seems that these registers contain things like the ability to stop > the counter or change its frequency. So we certainly don't want dom0 > getting at those! > > It's not clear to me if accesses to these registers are trapped > according to the controls available for the CP registers, or if we would > have to resort to trapping the entire MMIO page if we wanted to support > access to these registers (I don't think we would want to anyway). I didn't find any spec for the memory mapped timer. But looking to the driver, it looks like they also have the concept of physical/virtual. So we may not need to trap. Anyway, before implementing anything I'd like to find the corresponding spec. >> Signed-off-by: Julien Grall >> >> --- >> This patch is candidate to backport for Xen 4.5 and Xen 4.4. >> >> It may not apply correctly for Xen 4.4. >> --- >> xen/arch/arm/domain_build.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c >> index bf8dc78..16ce248 100644 >> --- a/xen/arch/arm/domain_build.c >> +++ b/xen/arch/arm/domain_build.c >> @@ -1047,6 +1047,7 @@ static int handle_node(struct domain *d, struct kernel_info *kinfo, >> DT_MATCH_COMPATIBLE("arm,psci"), >> DT_MATCH_PATH("/cpus"), >> DT_MATCH_TYPE("memory"), >> + DT_MATCH_COMPATIBLE("arm,armv7-timer-mem"), > > This is a bit less obvious that the other things in this list. Could you > perhaps add a comment? Sure. I will send a new version. Regards, -- Julien Grall