From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sheng Yang Subject: Re: [PATCH] KVM: VMX: Judge MMIO based on PFN rather than HVA in EPT violation Date: Wed, 11 Feb 2009 11:29:31 +0800 Message-ID: <200902111129.32148.sheng@linux.intel.com> References: <1234259021-26007-1-git-send-email-sheng@linux.intel.com> <20090210121432.GA29702@amt.cnet> <200902111043.45193.sheng@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , Avi Kivity To: kvm@vger.kernel.org Return-path: Received: from mga10.intel.com ([192.55.52.92]:44744 "EHLO fmsmga102.fm.intel.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752782AbZBKD3g (ORCPT ); Tue, 10 Feb 2009 22:29:36 -0500 In-Reply-To: <200902111043.45193.sheng@linux.intel.com> Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: On Wednesday 11 February 2009 10:43:43 Sheng Yang wrote: > On Tuesday 10 February 2009 20:14:32 Marcelo Tosatti wrote: > > Hi Sheng, > > > > On Tue, Feb 10, 2009 at 05:43:41PM +0800, Sheng Yang wrote: > > > One page can be unmapped from userspace, then HVA seems legal, but in > > > fact, PFN is illegal. > > > > > > Signed-off-by: Sheng Yang > > > --- > > > arch/x86/kvm/vmx.c | 6 +++--- > > > 1 files changed, 3 insertions(+), 3 deletions(-) > > > > > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > > > index 9913a1d..a4fa1b5 100644 > > > --- a/arch/x86/kvm/vmx.c > > > +++ b/arch/x86/kvm/vmx.c > > > @@ -3061,7 +3061,7 @@ static int handle_ept_violation(struct kvm_vcpu > > > *vcpu, struct kvm_run *kvm_run) u64 exit_qualification; > > > enum emulation_result er; > > > gpa_t gpa; > > > - unsigned long hva; > > > + pfn_t pfn; > > > int gla_validity; > > > int r; > > > > > > @@ -3086,8 +3086,8 @@ static int handle_ept_violation(struct kvm_vcpu > > > *vcpu, struct kvm_run *kvm_run) } > > > > > > gpa = vmcs_read64(GUEST_PHYSICAL_ADDRESS); > > > - hva = gfn_to_hva(vcpu->kvm, gpa >> PAGE_SHIFT); > > > - if (!kvm_is_error_hva(hva)) { > > > + pfn = gfn_to_pfn(vcpu->kvm, gpa >> PAGE_SHIFT); > > > + if (!is_error_pfn(pfn)) { > > > r = kvm_mmu_page_fault(vcpu, gpa & PAGE_MASK, 0); > > > if (r < 0) { > > > printk(KERN_ERR "EPT: Not enough memory!\n"); > > > > Forgot to drop the additional reference acquired by gfn_to_pfn ? > > Sadly, yeah... :( > > > Hum, gfn_to_hva assumes the slot information is accurate, which is not > > the case if you simply munmap a page in the middle of a slot... we > > should provide a helper in userspace, and make sure nothing bad can > > happen otherwise. > > Yes. But maintain a list in kernel seems a little complex for it. I checked > the callings of gfn_to_hva, seems most of them are safe with a inaccurate > result(not sure about host_largepage_backed, seems this would be affected > if one 4k page was unmapped inside a large page). > > > Anyway, why don't you just let kvm_mmu_page_fault handle instruction > > emulation instead of opencoding it in handle_ept_violation ? > > It didn't work as expect. Checking it. Oh, seems it didn't work due to my fault... Update the patch, thanks for reminder. :) -- regards Yang, Sheng