From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: Issues regarding "mem_access: Add helper API to setup ring and enable mem_access" Date: Fri, 27 Jun 2014 16:20:55 +0100 Message-ID: <1403882455.3169.72.camel@kazak.uk.xensource.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Tamas Lengyel Cc: Aravindh Puthiyaparambil , Ian Jackson , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On Mon, 2014-06-23 at 18:31 +0200, Tamas Lengyel wrote: > Hi everyone, > commit 6ae2df93c277b4093b3e54c9606387 > d1ba6d10fe into xen-staging includes a new function in xenctrl.h, > xc_mem_event_enable. This function name however has been used > previously in xenctrl.h up till at least Xen 4.1.2 for a different > purpose. We have been using autoconf to check which version of the > mem_access API is available in Xen by checking if xc_mem_event_enable > is available, signaling that the mem_access API is Xen 4.1 style, and > for xc_mem_access_enable signaling 4.2+ style API. See > https://github.com/bdpayne/libvmi/blob/master/configure.ac#L140 for > more details. > > > Now with this function being reintroduced, it becomes more complicated > to determine which version of the mem_access API does Xen actually > provide. A #define indicating mem_access API version would nicely > overcome this issue, or naming xc_mem_event_enable something else. Doesn't configure support checking for functions with a given prototype? > Furthermore, the new xc_mem_event_enable function unconditionally > unpauses the VM. This may not be a desired behavior in all cases, > especially if the VM was in a paused state when the function was > called. domain pauses are referenced counted on the hypervisor side. Ian.