From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH] vm_event: Record FS_BASE/GS_BASE during events Date: Thu, 11 Feb 2016 20:04:57 +0000 Message-ID: <56BCE969.9010307@citrix.com> References: <1455220260-5987-1-git-send-email-tlengyel@novetta.com> <56BCE6EA.5070501@bitdefender.com> <56BCE71B.1090003@citrix.com> <56BCE85B.2060005@bitdefender.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta4.messagelabs.com ([85.158.143.247]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1aTxU5-000461-Dn for xen-devel@lists.xenproject.org; Thu, 11 Feb 2016 20:05:01 +0000 In-Reply-To: <56BCE85B.2060005@bitdefender.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: Razvan Cojocaru , Tamas K Lengyel , xen-devel@lists.xenproject.org Cc: Keir Fraser , Jan Beulich List-Id: xen-devel@lists.xenproject.org On 11/02/16 20:00, Razvan Cojocaru wrote: > On 02/11/2016 09:55 PM, Andrew Cooper wrote: >> On 11/02/16 19:54, Razvan Cojocaru wrote: >>> On 02/11/2016 09:51 PM, Tamas K Lengyel wrote: >>>> While the public vm_event header specifies fs_base/gs_base as registers that >>>> should be recorded for each event, that hasn't actually been the case. In >>>> this patch we remedy the issue. >>>> >>>> Signed-off-by: Tamas K Lengyel >>>> Cc: Razvan Cojocaru >>>> Cc: Keir Fraser >>>> Cc: Jan Beulich >>>> Cc: Andrew Cooper >>>> --- >>>> xen/arch/x86/hvm/event.c | 9 ++++++++- >>>> 1 file changed, 8 insertions(+), 1 deletion(-) >>> Fair enough. >>> >>> Acked-by: Razvan Cojocaru >> Oops. >> >> Reviewed-by: Andrew Cooper > This has actually been intentional, in that we've only needed those > fields for EPT events, and thought that not filling what's not needed > until it's needed would save a tiny bit of hypervisor processing time. > They are being filled in only for page fault events at the moment. > > I believe it's been discussed at the time. We still don't need those > coming with the events that use hvm_event_fill_regs(), but if Tamas > needs them then by all means. The public header file does suggest that all of vm_event_regs_x86 will be complete. Are there any other fields currently missing? Given the overhead of the vmexit and communication on the vm_event channel, a few extra cycles reading state is lost in the overhead. ~Andrew