From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH] KVM: MMU: avoid fast page fault fixing mmio page fault Date: Thu, 18 Jul 2013 14:01:47 +0800 Message-ID: <51E784CB.1040402@linux.vnet.ibm.com> References: <1374123157-11142-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <20130718053154.GY11772@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: markus@trippelsdorf.de, mtosatti@redhat.com, pbonzini@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org To: Gleb Natapov Return-path: In-Reply-To: <20130718053154.GY11772@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 07/18/2013 01:31 PM, Gleb Natapov wrote: > On Thu, Jul 18, 2013 at 12:52:37PM +0800, Xiao Guangrong wrote: >> Currently, fast page fault tries to fix mmio page fault when the >> generation number is invalid (spte.gen != kvm.gen) and returns to >> guest to retry the fault since it sees the last spte is nonpresent >> which causes infinity loop >> >> It can be triggered only on AMD host since the mmio page fault is >> recognized as ept-misconfig >> > We still call into regular page fault handler from ept-misconfig > handler, but fake zero error_code we provide makes page_fault_can_be_fast() > return false. Yes. > > Shouldn't shadow paging trigger this too? I haven't encountered this on > Intel without ept. Since currently fast page fault only works for direct mmu. :)