From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: current not very current (vs curr_vcpu) Date: Sat, 20 Feb 2010 07:45:26 +0000 Message-ID: References: <20100219195003.6d1fb125@mantra.us.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100219195003.6d1fb125@mantra.us.oracle.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Mukesh Rathor Cc: "Xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On 20/02/2010 03:50, "Mukesh Rathor" wrote: > ah, I see what's going on. context_switch() is scheduling idle vcpu, and > calls continue_idle_domain() to reset_stack_and_jump(idle_loop). > well, reset_stack_and_jump() is setting rsp to guest_cpu_user_regs(), > and interrupt is coming right at that instant. so: > > diff = (char *)guest_cpu_user_regs() - (char *)(r) is 0 > > and as a result, guest_mode(regs) == true. Well, I don't see how this scenario works. If rsp==g_c_u_r() at the instant the interrupt comes in, then the stack frame for the interrupt will be *above* g_c_u_r(). Thus 'diff' in guest_mode() will evaluate non-zero and positive, and regs->{rip,rsp} should point at hypervisor code/stack. Also: in your original email you said regs.rsp pointed at dom0 stack. That doesn't tally with you saying that rsp==g_c_u_r() (an address in hypervisor space) immediately before the interrupt, in this email. Regs->rsp in the scenario you describe here should be exactly equal to g_c_u_r(). -- Keir