From mboxrd@z Thu Jan 1 00:00:00 1970 From: Razvan Cojocaru Subject: Re: Is it safe to assume that v == current in hvm_do_resume()? Date: Wed, 22 Oct 2014 12:10:13 +0300 Message-ID: <54477475.5010105@bitdefender.com> References: <544766BD.4020009@bitdefender.com> <5447733B.6010300@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5447733B.6010300@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: Andrew Cooper , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 10/22/2014 12:04 PM, Andrew Cooper wrote: > On 22/10/14 09:11, Razvan Cojocaru wrote: >> Hello, >> >> As far as I've understood the code, and based on several tests, it would >> appear that in xen/arch/x86/hvm/hvm.c, the struct vcpu *v parameter to >> hvm_do_resume() is always equal to current. >> >> Is that a reasonable assumption to make? I could have missed some use >> cases for the function. > > The calls look like this: > > {vmx,svm}_do_resume is the schedule_tail function pointer, which is a > no-return function and called on the way out of a context switch. > > They call hvm_do_resume() followed by a reset_stack_and_jump() to > {vmx,svm}_asm_do_vmentry. > > So yes - you can be guaranteed that the v in hvm_do_resume() is current. > > If you do come to explicitly rely on this behaviour, and it is in any > way unclear, it might be worth introducing an ASSERT(v == current) near > to the expectation. Thanks for the confirmation! Indeed, I had placed an ASSERT() before the code that needs v == current. Thanks, Razvan