From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [PATCH] pvh: Fix regression caused by assumption that HVM paths MUST use io-backend device. Date: Tue, 4 Feb 2014 10:32:58 -0500 Message-ID: <20140204153258.GA6847@phenom.dumpdata.com> References: <1391447001-19100-1-git-send-email-konrad.wilk@oracle.com> <1391447001-19100-2-git-send-email-konrad.wilk@oracle.com> <52F0B8F30200007800118E81@nat28.tlf.novell.com> <20140204144833.GE3853@phenom.dumpdata.com> <52F10F2402000078001190B7@nat28.tlf.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1WAi0q-0004lx-GZ for xen-devel@lists.xenproject.org; Tue, 04 Feb 2014 15:34:12 +0000 Content-Disposition: inline In-Reply-To: <52F10F2402000078001190B7@nat28.tlf.novell.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: Jan Beulich Cc: george.dunlap@eu.citrix.com, Konrad Rzeszutek Wilk , jun.nakajima@Intel.com, yang.z.zhang@Intel.com, xen-devel@lists.xenproject.org List-Id: xen-devel@lists.xenproject.org On Tue, Feb 04, 2014 at 03:02:44PM +0000, Jan Beulich wrote: > >>> On 04.02.14 at 15:48, Konrad Rzeszutek Wilk wrote: > > On Tue, Feb 04, 2014 at 08:54:59AM +0000, Jan Beulich wrote: > >> >>> On 03.02.14 at 18:03, Konrad Rzeszutek Wilk wrote: > >> > --- a/xen/arch/x86/hvm/vmx/vvmx.c > >> > +++ b/xen/arch/x86/hvm/vmx/vvmx.c > >> > @@ -1400,7 +1400,7 @@ void nvmx_switch_guest(void) > >> > * 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 ( get_ioreq(v) && get_ioreq(v)->state != STATE_IOREQ_NONE ) > >> > >> As Mukesh pointed out, calling get_ioreq() twice is inefficient. > >> > >> But to me it's not clear whether a PVH vCPU getting here is wrong > >> in the first place, i.e. I would think the above condition should be > >> || rather than && (after all, even if nested HVM one day became > > > > I presume you mean like this: > > > > if ( !get_ioreq(v) || get_ioreq(v)->state != STATE_IOREQ_NONE ) > > return; > > > > If the Intel maintainers are OK with that I can do it that (and only > > do one get_ioreq(v) call) and expand the comment. > > > > Or just take the simple route and squash Mukesh's patch in mine and > > revist this later - as I would prefer to make the minimal amount of > > changes to any code in during rc3. > > Wasn't it that Mukesh's patch simply was yours with the two > get_ioreq()s folded by using a local variable? Yes. As so >>From 6864786da87c4d67998a8ef46a3d289ac85074a9 Mon Sep 17 00:00:00 2001 From: Mukesh Rathor Date: Mon, 3 Feb 2014 11:45:52 -0500 Subject: [PATCH] pvh: Fix regression caused by assumption that HVM paths MUST use io-backend device. The commit 09bb434748af9bfe3f7fca4b6eef721a7d5042a4 "Nested VMX: prohibit virtual vmentry/vmexit during IO emulation" assumes that the HVM paths are only taken by HVM guests. With the PVH enabled that is no longer the case - which means that we do not have to have the IO-backend device (QEMU) enabled. As such, that patch can crash the hypervisor: Xen call trace: [] nvmx_switch_guest+0x4d/0x903 [] vmx_asm_vmexit_handler+0x4b/0xc0 Pagetable walk from 000000000000001e: L4[0x000] = 0000000000000000 ffffffffffffffff **************************************** Panic on CPU 7: FATAL PAGE FAULT [error_code=0000] Faulting linear address: 000000000000001e **************************************** as we do not have an io based backend. CC: Yang Zhang CC: Jun Nakajima Signed-off-by: Mukesh Rathor Signed-off-by: Konrad Rzeszutek Wilk --- xen/arch/x86/hvm/vmx/vvmx.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c index d2ba435..143b7a2 100644 --- a/xen/arch/x86/hvm/vmx/vvmx.c +++ b/xen/arch/x86/hvm/vmx/vvmx.c @@ -1394,13 +1394,13 @@ 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 *p = 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 ( p && p->state != STATE_IOREQ_NONE ) return; /* * a softirq may interrupt us between a virtual vmentry is -- 1.7.7.6