From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Dunlap Subject: Re: [PATCH] x86/vtsc: update vcpu_time after hvm_set_guest_time Date: Tue, 4 Jun 2013 11:28:05 +0100 Message-ID: <51ADC135.3050200@eu.citrix.com> References: <1370337050-2444-1-git-send-email-roger.pau@citrix.com> <2FCD40715DE006ED58FDA5F6@Ximines.local> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <2FCD40715DE006ED58FDA5F6@Ximines.local> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Alex Bligh Cc: Diana Crisan , xen-devel@lists.xen.org, Keir Fraser , Jan Beulich , Roger Pau Monne List-Id: xen-devel@lists.xenproject.org On 06/04/2013 11:24 AM, Alex Bligh wrote: > Roger, > > --On 4 June 2013 11:10:50 +0200 Roger Pau Monne > wrote: > >> When using a vtsc, hvm_set_guest_time changes hvm_vcpu.stime_offset, >> which is used in the vcpu time structure to calculate the >> tsc_timestamp, so after updating stime_offset we need to propagate the >> change to vcpu_time in order for the guest to get the right time if >> using the PV clock. >> >> This was not done correctly, since in context_switch >> update_vcpu_system_time was called before vmx_do_resume, which caused >> the vcpu_info time structure to be updated with the wrong values. This >> patch fixes this by calling update_vcpu_system_time after the call to >> hvm_set_guest_time has happened. > > I think this is the 'proper' fix to the bug Diana reported about > stuck clock - can you confirm? If so, we're happy to test this on > 4.3 and/or do try our hand at a backport to 4.2. Yes, and I was going to reply cc'ing you and Diana, but we're still having a technical discussion about where the best place is to put the fix. You may wish to wait until we have that resolved before testing the patch. -George