From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH] x86/hvm: simplify emulation triggered by vm_event response Date: Thu, 4 Feb 2016 12:36:33 +0000 Message-ID: <56B345D1.5090200@citrix.com> References: <1454588852-5389-1-git-send-email-rcojocaru@bitdefender.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1454588852-5389-1-git-send-email-rcojocaru@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 , xen-devel@lists.xen.org Cc: george.dunlap@eu.citrix.com, Tamas K Lengyel , keir@xen.org, jbeulich@suse.com List-Id: xen-devel@lists.xenproject.org On 04/02/16 12:27, Razvan Cojocaru wrote: > Currently, after receiving a vm_event reply requesting emulation, > the actual emulation is triggered in p2m_mem_access_check(), > which means that we're waiting for the page fault to occur again > before emulating. Presumably this means that we re-enter the guest and exit immediately for (hopefully) the same violation? > Aside from the performance impact, this > complicates the code since between hvm_do_resume() and the second > page fault it is possible that the latter becomes a completely > new page fault - hence checking that EIP and the GPA match with > the ones in the original page fault. Presumably this occurs when we injected an event on the vmentry? > If they don't, duplicate > EPT fault vm_events will occur, of which a monitoring application > needs to be aware. > This patch makes struct arch_vm_event smaller (since we no longer > need to track eip and gpa), removes the checking code from > p2m_mem_access_check(), and moves the emulation in hvm_do_resume(). > > Signed-off-by: Razvan Cojocaru > --- > xen/arch/x86/hvm/hvm.c | 17 +++++++++++++++++ > xen/arch/x86/mm/p2m.c | 34 ---------------------------------- > xen/include/asm-x86/vm_event.h | 2 -- > 3 files changed, 17 insertions(+), 36 deletions(-) Gotta love that diffstat! The logic makes sense, so Acked-by: Andrew Cooper for the x86-related nature, but it would be nice to have a review from Tamas for the vm_event side of things.