From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mukesh Rathor Subject: Re: [PATCH] Xen 4.4-rc3 regression with PVH compared to Xen 4.4-rc2. Date: Mon, 3 Feb 2014 11:26:05 -0800 Message-ID: <20140203112605.66306ae9@mantra.us.oracle.com> References: <1391447001-19100-1-git-send-email-konrad.wilk@oracle.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 1WAPAs-0008L5-U0 for xen-devel@lists.xenproject.org; Mon, 03 Feb 2014 19:27:19 +0000 In-Reply-To: <1391447001-19100-1-git-send-email-konrad.wilk@oracle.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: Konrad Rzeszutek Wilk Cc: george.dunlap@eu.citrix.com, xen-devel@lists.xenproject.org, yang.z.zhang@intel.com, jun.nakajima@intel.com, jbeulich@suse.com List-Id: xen-devel@lists.xenproject.org On Mon, 3 Feb 2014 12:03:20 -0500 Konrad Rzeszutek Wilk wrote: > I am hereby requesting an Xen 4.4 exemption for this bug-fix. > > The PVH feature is considered experimental, but it would be good to > have it working out of the box without crashing the hypervisor. > > Sadly that is not the case as 09bb434748af9bfe3f7fca4b6eef721a7d5042a4 > "Nested VMX: prohibit virtual vmentry/vmexit during IO emulation" > casues an NULL pointer dereference when starting a guest with 'pvh=1' > in the guest config. > > There are two ways of fixing this: > a). Add an '!xen_pvh_domain()' or '!xen_pvh_vcpu(current)' in the > path, or b). Check for ioreq() being NULL. This is actually done in > other places in the hypervisor - so I choose to piggyback on that. > I was about to send this patch on friday: diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c index d2ba435..563b02f 100644 --- a/xen/arch/x86/hvm/vmx/vvmx.c +++ b/xen/arch/x86/hvm/vmx/vvmx.c @@ -1394,13 +1394,14 @@ void nvmx_switch_guest(void) struct vcpu *v = current; struct nestedvcpu *nvcpu = &vcpu_nestedhvm(v); struct cpu_user_regs *regs = guest_cpu_user_regs(); + ioreq_t *ioreq = get_ioreq(v); /* * a pending IO emualtion may still no finished. In this case, * no virtual vmswith is allowed. Or else, the following IO * emulation will handled in a wrong VCPU context. */ - if ( get_ioreq(v)->state != STATE_IOREQ_NONE ) + if ( ioreq && ioreq->state != STATE_IOREQ_NONE ) return; /* * a softirq may interrupt us between a virtual vmentry is when I realized even after the above fix it is still crashing for me... debugging right now. JFYI. thanks Mukesh