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 10:43:43 +0800 Message-ID: <200902111043.45193.sheng@linux.intel.com> References: <1234259021-26007-1-git-send-email-sheng@linux.intel.com> <20090210121432.GA29702@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: Avi Kivity , kvm@vger.kernel.org To: Marcelo Tosatti Return-path: Received: from mga05.intel.com ([192.55.52.89]:49775 "EHLO fmsmga101.fm.intel.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752567AbZBKCnt (ORCPT ); Tue, 10 Feb 2009 21:43:49 -0500 In-Reply-To: <20090210121432.GA29702@amt.cnet> Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: 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. -- regards Yang, Sheng