From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752437Ab3F0JuU (ORCPT ); Thu, 27 Jun 2013 05:50:20 -0400 Received: from e23smtp06.au.ibm.com ([202.81.31.148]:50956 "EHLO e23smtp06.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751456Ab3F0JuS (ORCPT ); Thu, 27 Jun 2013 05:50:18 -0400 Message-ID: <51CC0AD0.3080003@linux.vnet.ibm.com> Date: Thu, 27 Jun 2013 17:50:08 +0800 From: Xiao Guangrong User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: Gleb Natapov CC: avi.kivity@gmail.com, mtosatti@redhat.com, pbonzini@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH v3 4/6] KVM: MMU: fast invalidate all mmio sptes References: <1370595088-3315-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <1370595088-3315-5-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <20130627082900.GD18508@redhat.com> <20130627090110.GE18508@redhat.com> <20130627091424.GA10758@redhat.com> <20130627092152.GB10758@redhat.com> In-Reply-To: <20130627092152.GB10758@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13062709-7014-0000-0000-0000033CF0A7 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/27/2013 05:21 PM, Gleb Natapov wrote: > On Thu, Jun 27, 2013 at 12:14:24PM +0300, Gleb Natapov wrote: >> On Thu, Jun 27, 2013 at 12:01:10PM +0300, Gleb Natapov wrote: >>> On Thu, Jun 27, 2013 at 11:29:00AM +0300, Gleb Natapov wrote: >>>> On Fri, Jun 07, 2013 at 04:51:26PM +0800, Xiao Guangrong wrote: >>>>> This patch tries to introduce a very simple and scale way to invalidate >>>>> all mmio sptes - it need not walk any shadow pages and hold mmu-lock >>>>> >>>>> KVM maintains a global mmio valid generation-number which is stored in >>>>> kvm->memslots.generation and every mmio spte stores the current global >>>>> generation-number into his available bits when it is created >>>>> >>>>> When KVM need zap all mmio sptes, it just simply increase the global >>>>> generation-number. When guests do mmio access, KVM intercepts a MMIO #PF >>>>> then it walks the shadow page table and get the mmio spte. If the >>>>> generation-number on the spte does not equal the global generation-number, >>>>> it will go to the normal #PF handler to update the mmio spte >>>>> >>>>> Since 19 bits are used to store generation-number on mmio spte, we zap all >>>>> mmio sptes when the number is round >>>>> >>>> So this commit makes Fedora 9 32 bit reboot during boot, Fedora 9 64 >>>> fails too, but I haven't checked what happens exactly. >>>> >>> Something wrong with gfn calculation during mmio: >>> >>> qemu-system-x86-17003 [000] 3962.625103: handle_mmio_page_fault: addr:c00ba6c0 gfn 100000000ba access a92 >>> qemu-system-x86-17003 [000] 3962.774862: handle_mmio_page_fault: addr:ffffb170 gfn 100000fee00 access a92 >>> >> Hmm, so I wounder why get_mmio_spte_gfn() does not clear gen bits. >> > Hmm, something like patch below fixes it. Will test more. > > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index 1fd2c05..aec9c05 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -260,7 +260,8 @@ static bool is_mmio_spte(u64 spte) > > static gfn_t get_mmio_spte_gfn(u64 spte) > { > - return (spte & ~shadow_mmio_mask) >> PAGE_SHIFT; > + u64 mask = generation_mmio_spte_mask(MMIO_MAX_GEN) | shadow_mmio_mask; > + return (spte & ~mask) >> PAGE_SHIFT; > } Looks nice. Gleb, thank you very much for investigating the bug and fixing my mistake. I will be more careful in the further developments.