From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: Questions about device/event channels in Xen. Date: Fri, 16 Mar 2007 08:45:31 +0000 Message-ID: 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.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Liang Yang , 'Mark Williamson' , xen-devel@lists.xensource.com Cc: "'Petersson, Mats'" , 'Daniel Stodden' List-Id: xen-devel@lists.xenproject.org On 16/3/07 06:02, "Liang Yang" wrote: > First: it seems Xen uses at least two different types of even "channels". > First type is for interrupt notification (upper call or uni-directional) and > the second if for the notification of queued descriptors (bi-directional). > So is the type of event channel fixed when Xen allocate them or not fixed > (for the same device), e.g. event channel 2 was a uni-directional type and > later can be changed to bi-directional type. An event channel can be allocated/deallocated many times during a domain's lifetime. The type of an event channel can change across allocations, but is fixed at allocation time for a particular allocate-to-deallocate period. > Second: as these events are handled asynchronously, does Xen treat different > type of event differently? For example, does Xen always respond to > interrupt event immediately (unlike queuing more descriptors and then set up > event)? Xen doesn't treat event delivery differently depending on type of event channel. What changes is the reason for kicking the event channel. > Third: for a PCIe device, I can choose to use MSI or the legacy line-based > interrupt. Does different type of interrupt handling mechanism affect the > event channel set-up? We don't support MSI yet, but the event-channel interface will not change when MSI is supported. The event channel will still be bound to a 'pirq'. -- Keir