From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops callsites to make them patchable Date: Tue, 20 Mar 2007 19:15:15 -0700 (PDT) Message-ID: References: <20070316.023331.59468179.davem@davemloft.net> <45FB005D.9060809@goop.org> <1174127638.8897.75.camel@localhost.localdomain> <20070318.003309.71088169.davem@davemloft.net> <20070318120814.GA45869@muc.de> <1174272469.11680.23.camel@localhost.localdomain> <1174348905.11680.54.camel@localhost.localdomain> <45FF4043.4000805@vmware.com> <45FF770C.7050301@goop.org> <46000C7E.4070001@goop.org> <46005B89.5070301@vmware.com> <46009E42.30400@vmware.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <46009E42.30400@vmware.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Zachary Amsden Cc: xen-devel@lists.xensource.com, akpm@linux-foundation.org, virtualization@lists.osdl.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, chrisw@sous-sol.org, Andi Kleen , "Eric W. Biederman" , anthony@codemonkey.ws, mingo@elte.hu, David Miller List-Id: virtualization@lists.linuxfoundation.org On Tue, 20 Mar 2007, Zachary Amsden wrote: > = > Actually, I was thinking the irq handlers would just not mess around with > eflags on the stack, just call the chip to ack the interrupt and re-enable > hardware interrupts when they left, since that is free anyway with the ir= et. No can do. Think level-triggered. You *need* to disable the interrupt, and = disabling it at the CPU is the easiest approach. Even so, you need to = worry about SMP and screaming interrupts at all CPU's, but if you don't = ack it to the IO-APIC until later, that should be ok (alternatively, you = need to just mask-and-ack the irq controller). > Maybe leaving irqs disabled is better. One of the advantages of doing that is that you only ever have a queue of = one single entry, which then makes it easier to do the replay. Linus